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Pupils’ prior beliefs about bacteria and science processes : their interplay in school science laboratory… Maxted, Margaret Anne 1984

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PUPILS' PRIOR BELIEFS ABOUT BACTERIA AND SCIENCE PROCESSES THEIR INTERPLAY IN SCHOOL SCIENCE LABORATORY WORK By MARGARET ANNE MAXTED B.Ed., The University of Exeter, 1977 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS in THE FACULTY OF GRADUATE STUDIES Department of Mathematics and Science Education  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA July, 1984 © Margaret Anne Maxted, 1984  In p r e s e n t i n g  this  requirements  f o r an  of  British  it  freely  available  understood  that  financial  shall  for reference  and  study.  I  for extensive be  her  copying or shall  g r a n t e d by  publication be  the  of  tomHOAATics  Pr*i_. Sopice.  The U n i v e r s i t y o f B r i t i s h 1956 Main Mall V a n c o u v e r , Canada V6T 1Y3  Date  DE-6  (3/81)  t*\  further  Columbia  eot*-cKuod  thesis  head o f  this  my  It i s thesis  a l l o w e d w i t h o u t my  permission.  Department o f  make  copying-of t h i s  representatives.  not  the  University  Library  h i s or  gain  the  the  s c h o l a r l y p u r p o s e s may by  f u l f i l m e n t of  I agree that  permission  department o r  for  in partial  advanced degree a t  Columbia,  agree that for  thesis  written  ABSTRACT School science laboratory tasks involve the use of conceptual frameworks and scientific processes. Shayer (1978) has criticized Nuffield science curricula for their alleged mis-match with.the average pupil's cognitive ability to perform laboratory tasks involving scientific processes such as controlling variables. Researchers interested in pupils' conceptual frameworks view the context of the experiment as a significant influence on the pupils' understanding of the experiment and i t i s thought that prior beliefs may interfere with the pupils' ability to control variables.  This  study examines qualitatively the interplay between the pupils' substantive beliefs about bacteria, prior to instruction, and their influence on understanding of the scientific processes in a laboratory experiment about bacteria.  Thirty-one pupils in the second year (12/13 year olds) of a secondary school in England were interviewed in order to e l i c i t their substantive beliefs about bacteria.  These pupils then followed a  series of two experiments taken from Nuffield Combined Science coursework.  Nine pupils were interviewed after each experiment to  ascertain their understanding of the task they had undertaken.  Two  groups of pupils for each experiment were audio-taped while they set up the experiment and their discussion of the questions about the task were recorded. Written work was also examined to cross validate views held by other members of the class.  It was found that pupils  whose prior beliefs included concepts of bacterial l i f e connected with reproduction were able to understand the role of the control in the  iiiexperiment. be varied.  Pupils' concepts of the growth of bacteria were found to Pupils who held less scientifically based concepts of  bacterial growth were unable to explain the use of the control plate. Some pupils who had more sophisticated prior conceptions of growth failed to use them in explanations about the control plate and showed signs that their beliefs concerning the design of the equipment interfered with their ability to understand the role of the control plate.  Prior beliefs were found to be a major influence on the  pupils' understanding of the experiment.  Teachers are recommended to investigate pupils' prior beliefs of the concepts being taught and encourage pupils to reflect upon the activity engaged in by the pupil during school science laboratory tasks.  -iv-  TABLE OF CONTENTS  Abstract  i i  List  of Tables  List  of Figures  ix x  Acknowledgements  xi  Chapter One 1.1  Introduction  1  1.2  Background t o the problem  2  1.3  Statement o f t h e problem  4  1.31  General  4  1.32  S p e c i f i c research questions  1.4  problem area  Some g e n e r a l m e t h o d o l o g i c a l  6  issues  7  Chapter Two 2.0  Psychological context  2.1  C o g n i t i v e i s s u e s versus  2.2  2.3  9 conceptual  issues  9  2.11  P i a g e t ' s work as used by Shayer  10  2.12  Alternative perspectives  15  Concept L e a r n i n g  21  2.21  25  Pupils  1  concepts o f b a c t e r i a p r i o r t o i n s t r u c t i o n  2.211  P u p i l s ' concepts o f l i v i n g t h i n g s  25  2.212  Pupils' classification  26  of l i v i n g things  2.22  P u p i l s ' a b i l i t y t o i s o l a t e and c o n t r o l v a r i a b l e s  28  2.23  The demands o f p u p i l s ' work i n the s c i e n c e c l a s s r o o m  34  Educational  implications  41  2.31  Instructional strategies  43  2.32  Laboratory  44  work  -V-  2.33  Problem solving  45  Chapter Three 3.0  Methods of study  48  3.1  Introduction  48  3.2  3.3  3.11  Background to methods used in the study  51  3.12  The c l i n i c a l interview  53  3.13  Classroom data  55  Methods of data collection  57  3.21  57  Data collection schedule  Description of the c l i n i c a l interview  59  3.31  Description of the taped small group discussions  61  3.32  Written work  63  3.4  The subjects  63  3.5  Analysis of data  65  3.51  Introduction  65  3.52  Analysis used in the study  67  Chapter Four 4.0  Introduction  69  4.1  Pupils' substantive beliefs concerning bacteria  70  4.11  74  4.2  Pupils' sources of information  Pupils' beliefs elicited from Clinical Interview Two  78  4.21  Pupils' identification of bacteria  78  4.22  Bacteria as living units Pupil significance of sterile equipment and medium Pupil significance of the control plate in the experiment  79 79  4.23  84  Pupils' overall understanding of the experimental procedures  85  -vi4.3  P u p i l s ' b e l i e f s e l i c i t e d from C l i n i c a l Interview Three  88  4.31  Predicted r e s u l t s  89  4.32  P u p i l s ' views on the s i g n i f i c a n c e of the s t e r i l e equipment and medium  4.33  P u p i l s ' views on the s i g n i f i c a n c e of the c o n t r o l plate i n the experiment  4.34  4.5  92  P u p i l s ' o v e r a l l understanding of the experimental procedures  4.4  90  93  P u p i l s ' perceptions of the two experimental tasks  95  4.41  Experiment One "Bacteria i n the A i r "  95  4.42  Experiment Two "Bacteria on Ourselves"  Results of group work (written answers)  101 103  Chapter Five 5.0  Introduction  108  5.1  Discussion o f p u p i l s ' b e l i e f s about bacteria  109  5.2  Discussion of p u p i l s ' i n t e r a c t i o n of the experiments i n the study 5.21  5.22  113  A n a l y s i s of concepts required t o understand the experiments  115  Pupils' prior beliefs  117  5.221  I d e n t i f i c a t i o n o f bacteria  117  5.222  The concept of colony  118  5.223  P u p i l s ' concepts o f s t e r i l i z a t i o n  119  5.224  P u p i l s ' perceptions of the r o l e of the c o n t r o l plate  5.3  122  P u p i l held concepts a f f e c t i n g the understanding o f the experiments  123  -vii-  5.31  Pupils' concepts of sterile  123  5.32  Pupils' concepts of growth  125  5.33  The influence of concepts on problem solving  127  5.4  Discussion of group work (written answers)  129  5.5  Pupils' perceptions of experimental tasks  132  5.6  Conclusions  136  5.7  Implications for the study  138  5.71  Implications for teaching  139  5.72  Implications for further research  143  References  146  Appendices A1 Example of a transcript produced from Clinical Interview One A2  159  Examples of concept maps produced from transcripts of Clinical Interview One  162  B  Description of experiments Experiment one "Bacteria in the Air" Experiment two "Bacteria on Ourselves"  167  C1  Example of a transcript produced from Clinical Interview Two  C2  Example of a transcript produced from Clinical Interview Three  D1  170  Example of a transcript produced from audio-taped group work of experiment one "Bacteria in the Air"  D2  168  172  Example of a transcript produced from audio-taped group work of experiment two "Bacteria on Ourselves"  177  -viiiE  Examples of work produced from group work Answers from three groups (D,E, and F) Questions: Experiment two "Bacteria on Ourselves" Answers from three groups (A,B, and C) Questions: Experiment one "Bacteria i n the A i r "  180  F  Examples of work produced from homework Questions: Experiment one "Bacteria i n the A i r " Answers from Nicole, Mark, and Robert Questions: Experiment two "Bacteria on Ourselves" Answers from three groups  183  -ix-  LIST OF TABLES  Table I  Summary of data gathering schedule for Experiment One  58  Table II Summary of data gathering schedule for Experiment Two • 5 9 Table III Number of pupils involved in interviews  64  -X-  LIST OF FIGURES  Figure I  Sample concept map produced by teacher for comparison against pupils' concept maps  24  -xi-  ACKNOWLEDGEMENT Many friends have given their support and advice during the writing of this thesis.  Without the support and cooperation of the  staff and pupils at Audley Park Secondary School this study would not have been possible.  I am grateful to them for showing tolerance  towards my demands. Also, i t would have been impossible to have contemplated completing my graduate program without the financial support received from The Rotary Foundation and Mr. T.J. Hooper. I thank them for their generosity.  I am grateful Dr. G. Erickson and  Dr. R. Carlisle who often provided counsel that encouraged me into new areas of thought. Finally, but not least, thank you to Jane Smith who typed the manuscript and bore the brunt of my moans and groans.  -1-  CHAPTER ONE 1.1  Introduction The context f o r the f o l l o w i n g study i s found i n the N u f f i e l d Combined  Science curriculum p r o j e c t , an English science scheme that followed from the implementation of N u f f i e l d '0' l e v e l science courses.  The Combined  Science team, s e t up i n 1966, had the task o f synthesizing these m a t e r i a l s to provide work s u i t a b l e f o r c h i l d r e n i n the f i r s t two years of B r i t i s h secondary schools (ages from 12 to 14). The project work produced by t h i s team has been used e x t e n s i v e l y i n secondary schools as a complete text and as a resource i n mixed a b i l i t y teaching (Booth, 1975) but has received c r i t i c i s m with regard t o i t s alleged mismatch with the average p u p i l s ' c o g n i t i v e operational l e v e l (Shayer, 1978).  This study has been c a r r i e d  out i n an E n g l i s h Secondary School with average a b i l i t y second year p u p i l s and focuses on c h i l d r e n ' s b e l i e f s about b a c t e r i a . I t i s b e l i e v e d that the context of the experiments used should be i n t e r p r e t e d more i n terms of the p u p i l ' s understanding of b a c t e r i a and the s c i e n t i f i c procedures involved i n the experiments than purely the operational l e v e l of the task (Donaldson, 1978). Although t h i s work has been c a r r i e d out i n a school i n England, the s e l e c t i o n of the concept area, the problem i n which the concept i s embedded and the issues surrounding  the r o l e of the p u p i l ' s  c o g n i t i v e operational l e v e l i n school performance are a l l a p p l i c a b l e to current curriculum issues i n science education a l l over the world (Wollman, 1978).  -2-  1.2  Background t o the problem Science c u r r i c u l a f o r average B r i t i s h secondary school p u p i l s have  often been based on other s y l l a b i intended f o r the c h i l d of above average ability.  Of the curriculum used i n teaching average a b i l i t y p u p i l s *  N u f f i e l d Combined Science subject matter draws heavily on the materials developed by the separate N u f f i e l d '0' l e v e l science teaching projects i n biology, chemistry, and physics (Charles, 1976).  Parts of the biology  component Combined Science draws from N u f f i e l d '0' l e v e l Biology which was not designed f o r the average secondary school p u p i l (Shayer, 1974). The r e s u l t i s that t e s t s , l i k e N u f f i e l d Combined Science, experimental  include  work which, according t o Shayer s (1974) a n a l y s i s require the f  p u p i l t o have reached the Piagetian stage of formal operational thought i n order t o understand some o f the s o p h i s t i c a t e d ideas presented. Shayer has argued, based on an a n a l y s i s of the N u f f i e l d '0' l e v e l Biology c u r r i c u l a from a Piagetian operational perspective, that only the eleven year o l d p u p i l with an i n t e l l i g e n c e quotient of at l e a s t 125 would be able t o cope with the l e v e l of t h i n k i n g presented i n these m a t e r i a l s .  The r e s t of the  school population, he suggests, would gradually acquire the required formal o p e r a t i o n a l s k i l l s a t l a t e r ages. This would mean t h a t most p u p i l s would have spent two or more years attempting  t o cope with problems and  experiments which required formal operational t h i n k i n g when i n f a c t they were only capable of using concrete operational s t r a t e g i e s t o understand the p r i n c i p l e s and concepts found i n these m a t e r i a l s .  I t would appear  that some "borrowed" N u f f i e l d '0' l e v e l concepts would be equally unsuitable f o r the lower a b i l i t y c l a s s as they appear i n the N u f f i e l d Combined Science scheme.  -3-  In contrast to Shayer's position, outlined above, Charles ( 1 9 7 6 ) claimed the Nuffield Combined Science course could be adopted for use with nearly the whole ability range.  His survey, of teachers' and pupils'  judgements and intuitions about the course in a large comprehensive school, concluded that most of the Nuffield Combined Science course i s suitable and useful for approximately the upper 7 5 percent of the ability range.  Below that i t becomes increasingly d i f f i c u l t to adopt the  curriculum, and therefore, he argued i t would be unsuitable for the lower ability pupils.  A similar view was held by Carter ( 1 9 7 6 ) who found the  majority of teachers believed that many sections were suitable for second year ( 1 3 year old) pupils.  Views held by Charles ( 1 9 7 6 ) , Carter ( 1 9 7 6 ) , and Shayer ( 1 9 7 4 ) show conflict between teachers' judgements on the suitability of Nuffield Combined Science curriculum materials and Shayer's theoretical analysis which suggests the unsuitability of these materials for the majority of secondary school pupils. Donaldson ( 1 9 7 8 ) sheds light on the situation by citing numerous examples of research work that shows that the context of the problem and the form of language in which i t was presented w i l l affect the success in finding the correct solution. She claims that the operational level demanded by a task may be altered depending on the context in which i t i s set.  It i s to this issue of the role of context  that other researchers have addressed their interest (Driver and Erickson, 1983;  Gilbert and Watts, 1 9 8 3 ) .  These researchers suggest that more  importance should be placed on how student beliefs are manifest in complex classroom environments and whether student's commonsense concepts become " c r i t i c a l barriers" (Hawkins, 1978) thereby limiting their understanding  -4-  of the disciplinary concepts presented by the curriculum. Research i s also being directed towards obtaining perceptions of students' difficulties and the understanding of pupils' "alternative frameworks" (Driver and Easley, 1978; Erickson, 1981) regarding the topic and the task we are asking the pupil to approach and master in the classroom.  Although Shayer argues from the standpoint of operational levels being the important criterion as to whether a particular concept w i l l be understood, he nonetheless concludes (Shayer, 1978) that when teachers attempt to find curricula most suitable for their pupils they search for how particular teaching routines match the understanding of the pupil. Researchers interested in pupils' alternative frameworks, although working from a different viewpoint, see that matching teaching routines to the pupils' understanding i s also an important goal.  This study examined the pupils' beliefs and strategies used in the classroom while conducting two scientific experiments on bacteria taken from the Nuffield Combined Science Course.  1.3 Statement of the problem 1.31  General problem area The experiments under study, "Growing Bacteria from the Air" and  "Bacteria on Ourselves", constitute two of the experiments in the Combined Science course unit on microbes and are also found in a similar form in many other texts used by average and lower ability pupils i n the secondary schools throughout the world.  -5-  In spite of Shayer's (1974) claim that similar experiments in Nuffield '0' level Biology are beyond the operational capacities of many of the pupils, the section on microbes in the Combined Science scheme was judged by curriculum developers to be suitable for average ability pupils although much of the material in this section involves the use of operational schemes found in the Piagetian stages 3A and 3B.  This study will identify student beliefs and strategies with respect to the subject matter and the context in which i t i s presented.  It i s  anticipated that as a result of the knowledge obtained from this study, teaching strategies may be devised to promote greater understanding of the subject matter.  The student's knowledge of the subject area may play an important role in determining how the pupil interprets the experiments.  It i s  believed the students w i l l already hold some beliefs about bacteria since microbes, although not visible, are often discussed in relation to disease so we may assume that these beliefs might have some influence on how the experiments are interpreted and understood.  Along with beliefs about the subject matter, the pupil's understanding of a scientific experiment (i.e. how one i s conducted, what conclusions can be made, what relevence does i t hold, etc.) may influence how the pupil approaches the' task and interprets the results.  From teaching experience the author recognizes that the pupils find difficulty in interpreting the results of these experiments successfully.  -6-  Pupils have shown that they do not recognize the importance of controlling variables in science experiments.  Insight into the pupils' use of their  knowledge and the alternative roles that they perceive the control plate in the experiment to play could be the result of their concept of a scientific experiment.  This could influence how the pupils reach  conclusions regarding the experimental data.  Understanding how pupils view experimental procedures may provide the teacher with a new perspective as to how to make other similar tasks more meaningful.  Often the teacher i s unaquainted with the concepts held by  the pupil, or how they were obtained.  In turn, the student i s often  unaware that his beliefs of a curriculum area are mismatched with those of the teachers.  In may instances the teacher follows a curriculum assuming  that pupils are working withing the same framework of the teacher's viewpoint of science. The teacher w i l l often modify the curriculum to suit the ability of the pupil without being aware of the alternative frameworks belonging to the pupil.  It i s hypothesized in the present  study that these frameworks have more importance in understanding the nature of the d i f f i c u l t i e s experienced by pupils in particular content areas than has been generally recognized.  1.32  Specific research questions The specific research questions that this study addresses are as  follows: 1)  What are the beliefs that pupils possess concerning bacteria before being formally taught? and  -7-  2)  How do pupils' beliefs concerning bacteria interact with their understanding of experimental procedures involved in the two experiments used in this investigation?  More specifically, the following aspects of the experimental setting w i l l be examined: a)  methods of identification of bacteria,  b)  bacteria as living units,  c)  significance of sterile equipment and medium,  d)  significance of a control in the experiments, and  e)  pupils' overall understanding of the experimental procedures.  1.4 Some general methodological issues The study was conducted in an urban English secondary school with pupils of the second year (12-13 years old). These pupils were of average ability (based on streamed classes in the year) for the whole of the school aged population. None of the pupils had been taught formally any aspect of the syllabus pertaining to bacteria prior to this study. Pupils had experienced teaching sessions concerning the concept of l i f e in their f i r s t year of secondary school. During this period of time they would also have had limited experience in laboratory practical work involving controlling variables.  It i s thought that the substantive beliefs  elicited by the interview technique of the f i r s t c l i n i c a l interview can be generalized to other groups of children of similar backgrounds and experiences.  Given the types of comments made i t would appear that the  experiences these pupils used in responding to the interview questions (e.g.  citing experiences from viewing television programmes, discussion  -8-  with health professionals) would be typical of most school pupils of this age in Britain and other western countries. It i s expected that after following the same topic in the curriculum project based laboratory work that pupils of average ability would reach conclusions and hold similar beliefs and assumptions about bacteria and the scientific processes of the two experiments studied. The teaching experience of the author lends support to these observations.  The strategy adopted to collect information concerning pupils' beliefs and how these are used in one particular set of laboratory tasks has been labour intensive.  The data gained has revealed a richness in  meaning that could not have been obtained by less time consuming techniques.  The author i s conscious of the possible criticism of this  type of research. The number of subjects involved in the interviews was relatively small and this raises questions to the restricted nature of the findings. An attempt at the cross validity of data was made by the use of written work both from group tasks and individual assignments.  An  understanding of the nature of the problems in teaching and learning can only be gained by intensive study of specific problems.  Larger scale  procedures tend to lack the required sensitivity needed to investigate actual learner problems and difficulties.  A range of accurate  descriptions of these problems and difficulties together with precise information as to the context in which the problems or d i f f i c u l t i e s occur w i l l be considerable use both to teachers and to curriculum developers.  -9-  CHAPTER TWO 2.0  Psychological context  2.1  Cognitive issues versus conceptual issues In the United Kingdom new examination s y l l a b i have placed demands on  basic s c i e n t i f i c s k i l l development.  Along with t h i s trend there has been  an i n c r e a s i n g l y obvious i n t e r e s t i n P i a g e t i a n developmental i t s curriculum development.  psychology  and  Piaget's stage theory produced the hope that  i n s t r u c t i o n would become more successful i f l e a r n i n g tasks matched the c o g n i t i v e stages already reached i n the p u p i l s ' p s y c h o l o g i c a l development. Other researchers i n t e r e s t e d i n pedagogy but not agreeing w i t h Piaget's emphasis on the stages of c o g n i t i v e development have sought a l t e r n a t i v e theories f o r improving teaching.  Many of these researchers (e.g. Novak,  1977a; Wollman, 1978) have c r i t i c i z e d the use of Piagetian theory as a base f o r research and have claimed that i t i s i l l - s u i t e d t o f i n d i n g ways of improving i n s t r u c t i o n since the v e r a c i t y of the stages have been questioned by many (Brainerd, 1978; Brown and Desforges, 1972).  I t has  been suggested that the concept of stages should be used f o r d e s c r i p t i v e convenience  only (Toulmin, 1971). L i t t l e i s known concerning the r u l e s of  t r a n s i t i o n from one stage to another despite Piaget's mechanisms of stage transition.  Discrepant evidence supporting the idea that Piaget's  operational s t r u c t u r e s can be widely taught leaves the question of t r a n s i t i o n a l i v e l y t o p i c f o r debate.  With the development of the N u f f i e l d Science schemes and t h e i r "modification" to s u i t the average secondary school p u p i l , researchers i n  curriculum development with a Piagetian bias asked several questions: "Was  previous p r a c t i c e i n science teaching, developed by adaptation t o the  top 15-20 percent of the school population, a s a t i s f a c t o r y model for the other 80 percent of p u p i l s ? Was i t p o s s i b l e to keep our e x i s t i n g models of science education while modifying them s u i t a b l y f o r the l e s s able p u p i l ? " (Shayer, 1979).  Piagetians maintain that l e a r n i n g takes place  most e f f e c t i v e l y when the c h i l d ' s present conceptual l e v e l ( c o g n i t i v e structure) i s matched c l o s e l y with the operational demands of the subject matter.  Shayer (1974) assessed the s e c t i o n being studied i n t h i s t h e s i s ,  b a c t e r i a and disease, as r e q u i r i n g a 3A minimal conceptual age and that the tasks being demanded of the c h i l d were at l e a s t one year ahead of the c o g n i t i v e development of s e l e c t i v e p u p i l s (top 15-20 percent of school population).  This suggests that p u p i l s not a t t a i n i n g l e v e l s of formal  thought w i l l not gain as much from the experience as those already at t h i s Piagetian stage.  Great i n t e r e s t has been shown i n the match of science  c u r r i c u l a to the l e a r n e r i n the middle and secondary school.  This match  i s s a i d t o have been achieved through an operational a n a l y s i s of the curriculum and the assessment of the p u p i l .  2.11  Piaeet's work as used bv Shaver Shayer's research program (Concepts i n Secondary Mathematics and  Science, 1974-1979) developed methods f o r analysing the curriculum and assessing the l e v e l of t h i n k i n g of the p u p i l population.  Both the  a n a l y s i s and assessment have been c r i t i c i z e d with respect t o experimental design and Shayer's heavy r e l i a n c e on a P i a g e t i a n framework ( D r i v e r , 1979; Wollman, 1978).  This framework was used as i t was thought p o s s i b l e to  analyse both the demands of the curriculum and provide a method of  -11-  e s t i m a t i n g the c o g n i t i v e l e v e l o f the p u p i l . The u n d e r l y i n g model of CSMS work assumes P i a g e t i a n t e s t s do t e s t c o g n i t i v e development. Shayer (1981) r e j e c t s the a l t e r n a t i v e i n t e r p r e t a t i o n that the Piagetian t e s t s measure the p u p i l s ' grasp o f concepts they have learned and not c o g n i t i v e development.  A taxonomical method was implemented f o r analyzing the Piagetian l e v e l o f t h i n k i n g demanded by a Science Curriculum (Shayer, 1972). This was achieved by assessing the l e v e l of o p e r a t i o n a l development possessed by the c h i l d i n Piagetian terms then p r e d i c t i n g the supposed Piagetian l e v e l of t h i n k i n g demanded by an examination o f the content objectives and exam items o f the course.  The exam items were c l a s s i f i e d beforehand f o r  supposed Piagetian c o g n i t i v e stage development required f o r t h e i r comprehension.  Only p u p i l s a t the 3A stage of formal thought were  considered t o have an opportunity t o succeed on tasks designated as being 3B i n c o g n i t i v e demand.  C r i t i c i s m has been l e v e l e d a t t h i s a n a l y s i s (Driver, 1979) since the l o g i c a l demands o f the task may not be problematical t o the p u p i l but the context i n which these demands l i e , due perhaps t o the pedagogical approach adopted, may cause the pupil t o be unable t o cope with the c o g n i t i v e task.  Other researchers have suggested that memory demands may  a f f e c t the l o g i c a l performance on a problem (Pascual-Leone, 1969). Formal stage performance may r e f l e c t acquired knowledge t o a greater extent than acknowledged by Piaget (Wollman, 1978). One o f Wollman's c r i t i c i s m s o f p l a c i n g tasks i n l e v e l s o f cognitive demand i s that i n a s t a t i s t i c a l sense, the w i t h i n group variance of the tasks i s too great t o be u s e f u l .  -12-  He claims that Shayer's methods "have relied on either the prima facia similarity of a school concept within a Piagetian one or the researcher's best guess as to the d i f f i c u l t y of the concept. Since most school science concepts are not very similar to Piagetian concepts, informed guesswork has been the method of choice" (p. 42).  In Shayer's work the second component of the research, the method assessing the pupil's level of thinking, required the development of group tests along with data collected from a large enough population to be representative of secondary school pupils.  Data concerning the  development of thinking abilities in these pupils was essential for curriculum matching as i t was impractical to think that the original Genevan work (Inhelder and Piaget, 1958), assuming that a l l adolescents reached formal thought, would apply in Britain.  Instead, i t was assumed  that any level of thinking from pre-operational to late formal operational might be shown by different pupils.  About 30 percent of 15 year old  pupils demonstrated formal thinking ability with the rest showing a wide spread of cognitive ability (Shayer, Kuchemann, Wylam, 1976; Shayer and Wylam, 1978).  Driver (1979) criticizes the establishment of national norms as a hazardous procedure especially when only two tasks are used in the assessment testing early ( 3 A ) or late (3B) formal thinking. There i s a danger that pupils may perform indifferently on one or other of the tests and be classified as non-formal. An earlier attempt by Shayer (1974) used IQ scores as a classifying standard.  The general finding in this area i s  that Piagetian tests sometimes correlate moderately with IQ and scholastic  -13-  achieveraeht but again are not sensitive enough to be generalizable.  Alternative theorists in cognitive development have objected to the classification stages of the Piagetian model. Shayer (1979) has realized the doubt cast on the validity of Piaget's work by other researchers (Lunzer, 1973; Brown and Desforges, 1977) but in taking a "very hard hosed empirical view" and using Piaget's experimental methods, his idea was to show that performances at the same Piagetian level from task to task would be maintained. In his summary of the empirical evidence he claims support for Piaget's account of formal operational thinking.  Piaget's formal operational stage has come under heavy criticism from other workers.  Odum (1978) suggests that the problem of decalage (i.e.  the concept i s achieved with different tasks at different times) has proved decisive in the downfall of the usefulness of the stages of Piaget's theory.  The theory i s unable to predict performance and  performance i s the ultimate criterion for judging learning outcomes. Performance variability on tasks, supposedly demonstrating formal thought, have limited our knowledge of developmental  theory, argues Wollman (1978).  Grouping tasks in the same logical classifications has been seen to be unwise since from a performance perspective they are not a l l equivalent. Piagetian logical operations have been shown not to relate to performance and many researchers (Falmagne, 1975; Brainerd, 1977b; Revlin and Mayer, 1978; Siegel and Brainerd, 1978) have argued the insufficiency of concrete and formal logical operations on the ground that the postulated stages f a i l to show their discreteness. Piaget's description of formal operations i s quite confusing and i t i s d i f f i c u l t to understand the exact  -14-  meaning of the term.  There i s considerable question as to the time of  emergence of the formal operation dealing with verbal propositions (e.g. i f then statements). In respect to the INRC problems, Easley (1964) noted the occurence of this ability much earlier than Piaget would maintain.  Increasing numbers of studies show that abstract or formal operational tasks can be handled by young children.  Ennis (1976) has  shown that children in grades 1-3 (6-8 years) can use forms of conditional logic and Kuhn (1977) has observed that conditional reasoning can take place in concrete conversational situations.  Donaldson (1978) suggests  that thinking which no longer operates in a supportive context and i s often called 'formal' or 'abstract' should not be equated with 'formal operational thought' as determined by Piaget, but should instead be termed disembedded.  She cites more evidence that the context of the task i s as  important as the task i t s e l f when attempting to classify a task as e l i c i t i n g formal operational thought from a pupil.  Munby's (1980)  criticism i s that the research community i s running the risk of being careless i f the notion of being at a stage i s used.  The ambiguities in  research reports abound as to who w i l l have reached formal operational thought by a certain age and what forms of reasoning constitute this stage.  Munby reports that the temptation i s to "take things quite  l i t e r a l l y , to lose sight of the syntax and to begin to award the notion of stages a status i t does not deserve" (p. 130). The designing of curriculum and teaching strategies according to definite stages may be unwise especially in the light of views held by Brown and Desforges (1977). They make the point that "the exact proportion of heterogeneity which theorists w i l l tolerate without abandoning the stage concept, i s an  -15-  interesting one" (p. 1 1 ) . This statement lends support to Driver's (1979) criticism of Shayer's use of tasks to analyse the middle and secondary school population, claiming that tasks used were not successful in defining formal thought to a particular level and cannot be compared to class tests due to their differing contexts.  It is doubtful i f Piagetian stages can be used as indicators of "readiness" for sequencing subject matter in the curriculum. The discussion of sequence revolves around the question of how concrete or abstract the learning experiences must be at various stages of development. We have already seen evidence that tasks vary in their cognitive difficulty depending on their context.  Many educators treat  Piaget's observations as i f they are final statements in the theory about intellectual development and these observations are then used to determine content of the curriculum without considering other evidence or holding reservation.  Appraisal of Piaget's implications shows the structure and  sequencing of subject matter as somewhat pessimistic.  2.12  Alternative perspectives Theorists like Shayer are mainly concerned with the development of  frameworks for studying cognitive development. Acceleration of cognitive development i s effected by basing the teaching-learning process on theory. Piaget's educational contribution i s in the area of structure and sequencing of subject matter at appropriate developmental levels.  Many  researchers have spent a lifetime's work suggesting pedagogical strategies to promote efficient learning in contrast to the Piagetian ideas of matching the level of difficulty of the task involved with the cognitive  -16-  development present i n the c h i l d ' s t h i n k i n g c a p a b i l i t i e s .  These  researchers see the problems as more content and context s p e c i f i c and have spent time i n v e s t i g a t i n g t o p i c s which create teaching d i f f i c u l t i e s .  Gagne, Ausubel, and Bruner place l e s s emphasis on Piaget's operational s t r u c t u r e but more on how  information i s processed.  Ausubel  (1963, 1968) does not view h i s theory i n opposition t o Piaget's.  The  key  issue i s "whether c h i l d r e n develop general 'cognitive s t r u c t u r e s ' or 'cognitive operations' t o make sense out of experience, or i f instead, they acquire a h i e r a r c h i c a l l y organized framework of s p e c i f i c each of which or some combination  concepts,  permits them to make sense out of  experience" (Novak, 1977b, p. 455).  Novak believes that c h i l d r e n acquire  a h i e r a r c h i c a l l y organized framework of s p e c i f i c concepts and do not develop general cognitve operations as Piaget's theory claims. S i m i l a r l y for Bruner (1965) the s t r u c t u r e of the t o p i c l i e s i n the d i s c i p l i n e considered; how things are r e l a t e d w i t h i n a p a r t i c u l a r d i s c i p l i n e . Piaget's concept of s t r u c t u r e d i f f e r s from Bruner's since Piaget develops the idea of the c h i l d a c t i v e l y s t r u c t u r i n g h i s experience throught the operation.  "An operation i s thus the essence of knowledge, i t i s an  i n t e r i o r i z e d a c t i o n , which modifies the object of knowledge..." (Piaget, 1964, p. 8 ) . c h i l d ' s mind.  For Piaget the concept of s t r u c t u r e i s a property of the Duckworth (1964) contrasts Bruner with Piaget on the idea  of structure i n the curriculum: "The question comes up whether t o teach the s t r u c t u r e or to present the c h i l d with s i t u a t i o n s where he i s a c t i v e and creates the s t r u c t u r e s himself.... The goal i n education i s not to increase the amount of knowledge, but to create the p o s s i b i l i t i e s for the c h i l d t o invent and discover" (Duckworth, 1964, p. 3).  -17-  Since every pupil has their own way of structuring and attempting to dechiper the world around them, a class w i l l possess many unique learning styles and viewpoints.  Readers of Piaget can conclude that the child  structures the world in ways quite different from adults. Appreciation of other types of concept construction may facilitate the communication of knowledge. Bruner (1965) remarked that i f we present topics in the way children perceive things then the subject can be taught effectively underlining the basic concepts. the child's viewpoint.  Unfortunately teachers often do not know  Bruner's method of teaching i s to induce  understanding by tying down isolated segments of knowledge.  The  development of basic transformations of cognitive structure i s not in terms of S-R bonds as in Gange's tradition but of organized wholes and systems of inter-relationships.  The action of the person on the  environment leads to the development of a cognitive structure with this structure possessing an equilibrium and greater balance between ideas. The optimum sequencing of this action i s not step by step, in Bruner's view, but to allow the pupil the opportunity to organize their own learning according to their own requirements. Bruner advocates the spiral curriculum so that by the time subjects are presented a second time the pupil's knowledge has both broadened and deepened and therefore becomes more specialized.  This style of learning places emphasis on the child to  discover and learn.  In contrast, Ausubel sees the teacher as being more influential. Piaget's ideas about verbal learning place severe limitations on the curriculum maker. Bruner, however, i s optimistic concerning the role of language as a coordinator and integrator of experience.  Likewise  -18-  Ausubel's perspective i s more of an interactionist approach using verbal, didactic learning to aid the formation of concepts.  He criticizes the  Piagetian view for over emphasizing the person and behaviourists for their heavy emphasis on the influence of the environment. Ausubel et a l . (1978) have concentrated on cognitive process in school learning and describe the pupil as f i t t i n g new units of information into a category of preconceptions already  held by the learner.  New learning i s seen as a  process of subsumption by preconceptions (Ausubel, 1963). From studies reviewed by Driver and Easley (1978) there seems to be reasonable grounds to suggest these preconceptions may be resistant to instruction. Since "new  learning" i s related to a large array of information the pupil  already possesses (Novak, 1976) i t i s understandable why confusion arises in obtaining the 'correct' concepts when their prior conceptions are often based on a very different perspective of the world.  The task of the  school, explained by Ausubel in his meaningful verbal learning (1963), is to identify clear, stable, and organized bodies of knowledge within disciplines so that the learner incorporates them meaningfully own system.  into his  Meaningful verbal learning depends on the nature of the  material learnt, whether abstract or not in nature, and the availability in the subject's cognitive structure of relevant subsuming concepts for those being taught.  The two criteria of non-arbitrariness and  substantiveness gives the material its logical meaning. Its non-arbitrariness i s the relationship of the new item and i t s congruency with the person's existing ideas whilst substantiveness  concerns the  meaning of the relationship withing different but equivalent semantic contexts.  With this theory of concept acquisition Ausubel recommends the  use of advanced organizers to structure and sequence instruction but prior  -19-  t o t h i s , the teacher should possess some i n s i g h t i n t o the knowledge possessed by the t y p i c a l p u p i l .  Discovery of the c h i l d ' s point of view i s also a recommendation made by Margaret Donaldson (1978).  She c i t e s research which claims that  c h i l d r e n given a task with "human sense" i . e . a problem that does not possess abstract terms, the task w i l l be more s a t i s f a c t o r i l y solved and the p u p i l shows l e s s egocentrism and i n a b i l i t y t o decentre.  Piaget  considers that the growth of the a b i l i t y t o decentre i s c r u c i a l since the making o f inferences demands s k i l l i n the f l e x i b l e s h i f t i n g of point of view.  Donaldson claims that there i s good reason t o doubt whether the  c h i l d ' s d i f f i c u l t y with decentring i s as severe and widespread as Piaget claims.  In order to improve the a c q u i s i t i o n of s k i l l s i t i s suggested  that the c h i l d understand the general nature of the l e a r n i n g a c t i v i t y . This makes great demands on the teacher's capacity t o decentre since "an adult's knowledge of the general nature of the subjects taught t o c h i l d r e n when they f i r s t enter school i s apt t o be so w e l l e s t a b l i s h e d that i t blocks the r e a l i z a t i o n of p r e c i s e l y what the c h i l d r e n need t o be helped t o see" (Donaldson, 1978, p. 100). This could be the case i n secondary schools as w e l l . The c h i l d ' s approach to science may be determined by the concepts he/she sees as important and not those that the teacher sees as necessary.  The s i g n i f i c a n c e of  s c i e n t i f i c procedures may not be relevant t o the p u p i l i n the science laboratory.  Teachers need t o gain i n s i g h t i n t o what p u p i l s consider  relevant i n order t o make science more meaningful.  Making school science meaningful has been the purpose of the two dominant viewpoints that have influenced research on l e a r n i n g and problem  -20-  solving.  Piagetian researchers such as Lawson (1975, 1979), Renner and  Stafford (1972), and Walker, Hendrix and Mertens (1980) argue that the developmental stage of a student can be used to predict or account for success or failure with particular aspects of science.  Those researchers  in the Ausubelian tradition (Novak, 1977c) argue that relevant prior conceptual knowledge i s the most important factor in learning science content as well as using that knowledge to solve problems.  The  relationship between students' conceptual knowledge and problem solving strategies i s emerging from a third perspective. As an example, Greeno's (1978a) work emphasizes the interrelationships between the conceptual knowledge possessed by problem solvers and their knowledge of the procedures they use to solve problems. problem solving.  He calls this meaningful  Detailed analysis of the conceptual and procedural  knowledge that students use and learn from instruction may provide further basis for changing science instruction.  -21-  2.2  Concept learning There i s considerable evidence from recent research of the important  role played by the ideas that children bring with them to school. It i s not sufficient to limit oneself to the discovery of specific deficiencies inherent in student's viewpoints compared with the expert's knowledge, but for every lesson the teacher should attempt to appreciate the many mental and physical processes that are prompted into action i n order that the lesson be effective in terms of the teacher's aims and objectives.  The aim of every teacher i s to promote the pupils' acquisition of correct scientific concepts.  When a concept has been meaningfully learnt  or acquired the student can define i t s c r i t i c a l attributes and consequently recognize new, unfamiliar instances of the particular concept (Bruner et a l . , 1956; Ausubel, 1968; Klausmeier et a l . , 1974; Herron et a l . , 1977). Klausmeier (1976) has produced five levels of concept mastery based on the pupils* ability to define the attributes of a concept. The everyday use of language can hinder the ability of the pupil to define the attributes of a concept (Vygotsky, 1962). An example of this i s the often used false distinction between animals and birds.  The ability to assign  birds to the same group called animals requires the pupils to remove the division placed by everyday language and assign examples to their class on the merits of their defining attributes.  The ability to assign correctly  to i t s class examples of the concepts i s required in the third of the five levels of concept mastery proposed by Klausmeier (1976).  The five levels  of concept mastery according to Kausmeier (1976) can be summarized as follows:  -22-  Level 1  The a b i l i t y to use the word correctly or respond to i t appropriately i n conversation.  Level 2  The a b i l i t y to give spontaneously, examples of the concept, e.g. to provide examples of l i v i n g things.  Level 3  The a b i l i t y to assign c o r r e c t l y to i t s class examples of the concept, e.g. to c l a s s i f y  Level 4  l i v i n g or non l i v i n g things.  The a b i l i t y to give verbally some basis for the  classification,  e.g. to say what l i v i n g things do that non l i v i n g things don't. Level 5  The a b i l i t y to c l a s s i f y  instances and non instances accurately  and to show f u l l knowledge of a l l the defining attributes of the concept. In the process of concept learning there may individual's conceptual  well be a requirement for the  framework to undergo change i n order that the  b i o l o g i c a l concept becomes more precise.  Within the epistemological framework of conceptual change there  has  been developed two mechanisms of change - the "revolutionary" and the "evolutionary" process.  Strike and Posner (1982) regard the deep  restructuring of knowledge by the learner as a "large scale" change of 'accomodation'.  This revolutionary change would be hindered by e x i s t i n g  b e l i e f s acting as 'stumbing blocks' (West, 1982) and would seem a d r a s t i c conceptual process.  In contrast, the evolutionary change t i d i e s up the  student's b e l i e f s and these may 1982) for change.  The "small s c a l e " change or "assimilation" that S t r i k e  and Posner (1982) suggest may old and new  even provide the 'building blocks' (West,  knowledge.  be prompted when teachers attempt to l i n k  -23-  In order to understand the difference between pupils' beliefs and teachers' beliefs, teachers may need to know the beliefs students bring to the classroom and the concepts that are to be learnt.  In the experiments  investigated by this study there are three broad components that may influence the pupils' understanding of the results of the experiments. These are:  1)  prior beliefs held concerning bacteria,  2) the cognitive procedures used in isolating variables and controlling them, and 3) the demands of laboratory work, e.g. using new apparatus, accomodating new instructions, both written and verbal.  -24-  FIGURE I  Sample concept map produced by teacher f o r comparison against p u p i l s ' concept maps  NITROGEN CYCLE  caused by  used in PLANT/ANIMAL MATERIAL  PATHOGENIC  breakdown  because MICROSCOPIC HARr Fill  USEF UL  8ACTERIA are LIV INS  GJKM  MOVE  by AIR WATER GROWTH  REPRODUCE  1*  SENS ITIVE  RESP IRE by  ltd ANTIBI OTICS  INCRE-ASE IN CYTOP1ASH DISEASE I producM CONSUME S  PRODUCERS art  SAPROPHY IC  are AUTOTROPHIC  break down F000 MATERIAL  build up  -25-  2.21  P u p i l s ' concepts o f b a c t e r i a p r i o r t o i n s t r u c t i o n  I t i s p o s s i b l e t o examine the many concepts a s s o c i a t e d w i t h the term b a c t e r i a by g e n e r a t i n g a concept map. person's u n d e r s t a n d i n g o f t h a t term. produced  The concept map r e p r e s e n t s one F i g u r e 1 i l l u s t r a t e s a concept map  by t h e a u t h o r . The terms i n t h e boxes a r e c o n c e p t s and t h e s e a r e  connected by p r o p o s i t i o n s t o o t h e r c o n c e p t s . A comparison  o f a t y p i c a l map  drawn by a p u p i l w i t h t h a t o f one drawn by the t e a c h e r may a s s i s t t h e t e a c h e r t o understand b e t t e r some o f the d i f f i c u l t i e s e x p e r i e n c e d by p u p i l s i n i n t e r p r e t i n g a g i v e n i n s t r u c t i o n problem. understand t h e r o l e o f b a c t e r i a i n t h e experiments  F o r example, t o the p u p i l must have  some u n d e r s t a n d i n g o f the concept o f " l i v i n g t h i n g s " and s i z e o f "bacterial  2.211  organisms".  P u p i l s ' concepts o f l i v i n g t h i n g s  Although t h e r e has never been a s i n g l e d e f i n i t i o n o f the concept o f l i f e t h a t would be s a t i s f a c t o r y t o many b i o l o g i s t s , seven o f l i v i n g organisms  used i n s c h o o l a r e 1) growth, 2) r e p r o d u c t i o n , 3)  r e s p i r a t i o n , 4) n u t r i t i o n , 5) e x c r e t i o n , 6) i r r i t a b i l i t y , locomotion.  characteristics  and 7)  These seven c h a r a c t e r i s t i c s b e t t e r i l l u s t r a t e the animal  kingdom a t m u l t i c e l l u l a r l e v e l s .  I t i s not s u r p r i s i n g t h a t the concept of  b a c t e r i a as a l i v i n g u n i t may be more d i f f i c u l t because  i t i s n o t obvious  t h a t they comply w i t h any o f the above c h a r a c t e r i s t i c s s i n c e they a r e so s m a l l . P i a g e t (1929) i d e n t i f i e d f o u r s t a g e s which c h a r a c t e r i z e the development o f the " l i f e c o n c e p t " i n c h i l d r e n .  The f i n a l stage a c h i e v e d  by e l e v e n y e a r o l d c h i l d r e n and upwards showed t h e a b i l i t y  to correctly  i d e n t i f y o n l y l i v i n g c r e a t u r e s a s b e i n g a l i v e and p o s s e s s i n g  -26-  consciousness.  L i f e has many meanings as f a r as c h i l d r e n are concerned.  From a  study of 83 students, grades 5-9, 45 percent understood the c o n t i n u i t y of l i f e (Tamir et a l . , 1981).  T h i r t y - s i x percent r e a l i z e d that l i v i n g  organisms o r i g i n a t e from other l i v i n g organisms, but were not able t o e x p l a i n t h i s r e l a t i o n s h i p . Nineteen percent b e l i e v e d t h a t " i t i s p o s s i b l e for l i v i n g organisms to develop from n o n l i v i n g " .  Ninety-nine percent of  c h i l d r e n from grade 4 c l a s s i f i e d animals as l i v i n g .  Simpson and Arnold (1982) found a l l the primary p u p i l s interviewed could use the words ' l i v i n g things' appropriately.  They found that the  performances of p u p i l s i n the f i r s t two years of secondary school (12 and 13 year olds) were not markedly improved i n the c l a s s i f i c a t i o n of l i v i n g and non l i v i n g over the primary p u p i l s .  F i f t y percent of the fourth year  (15 year olds) biology p u p i l s were s t i l l unable to c o r r e c t l y c l a s s i f y eighteen items.  "A" l e v e l students found d i f f i c u l t y i n d i s t i n g u i s h i n g  between ' a l i v e and dead* and 'dead and non l i v i n g ' i n set tasks (Brumby, 1982). Even c h i l d r e n who c o r r e c t l y c l a s s i f i e d sixteen items as l i v i n g and non l i v i n g "possessed an imcomplete understanding of l i v i n g according t o associated b i o l o g i c a l a t t r i b u t e s (such as) n u t r i t i o n ... r e s p i r a t i o n ... reproduction" (Looft, 1974, p. 289).  2.212  P u p i l s ' c l a s s i f i c a t i o n of l i v i n g things Researchers have a l s o examined p u p i l s ' a b i l i t y t o c l a s s i f y l i v i n g and  non l i v i n g objects.  I t appears that i t i s e a s i e r to c l a s s i f y animals as  l i v i n g organisms than p l a n t s .  The a b i l i t y to c l a s s i f y has been regarded  -27-  by psychologists as an important aspect of the c o g n i t i v e process.  It is  based upon the formation, by the p u p i l , of precise concepts and the development of systematic ways of r e l a t i n g them to each other ( L o v e l l , 1968). Gagne (1970) suggests t h a t there are two kinds o f concepts:  those  of a concrete type that are derived from the experience of many examples, and those of a defined type that are more abstract i n nature and derived from d e f i n i t i o n s .  Some classes of l i v i n g organisms are of the  concrete  type since r e a l or p i c t o r i a l examples can be presented whereas other classes of l i v i n g organisms r e l y on verbal d e f i n i t i o n e.g. the d i f f e r e n c e between amphibians and r e p t i l e s .  Ryman (1974) found that many twelve year olds i n a comprehensive school were unable to c l a s s i f y plants and animals i n t o c l a s s e s . With a few exceptions they d i d not possess r e l i a b l e c l a s s concepts. This was  revealed  by t h e i r i n a b i l i t y to recognize instances and non instances of the concepts.  The misunderstandings revealed suggest that inadequate concept  formation and language problems contribute to the d i f f i c u l t i e s of c l a s s i f y i n g plants and animals. The c l a s s i f i c a t i o n of s t a r f i s h and j e l l y f i s h as " f i s h " i l l u s t r a t e s t h i s problem. A study of t h i r t y - n i n e ten to f i f t e e n year olds revealed t h a t a l l but s i x used the number of legs t o c a t e g o r i z e instances and non instances of the concept of "animal".  The  common meaning of the word "animal" appeared to r e f e r to the r e s t r i c t e d category of the four-legged, t e r r e s t r i a l rnammals. Size was used as a c r i t e r i o n by approximately  one t h i r d of the p u p i l s at l e a s t once. Results  showed t h a t the smaller the organism the l e s s l i k e l y i t would be animal. A few p u p i l s used the c r i t e r i o n of movement as an a t t r i b u t e of l i v i n g things ( B e l l , 1981).  -28-  Simpson and Arnold  (1982)  and others have shown that pupils who have  experienced two years of secondary school science do not posses a precise concept of l i v i n g things, despite the fact that their science courses were designed to teach this concept. There was also a considerable gulf between the level of concept attainment actually reached by the pupils and the level of attainment assumed by the teachers.  It i s unlikely to be useful  to commence teaching about bacteria in the second year when "living" i s a vague, unstable concept, the word "animal" takes on diverse meaning, and bacteria in their physical sense are so small as to be non-existent.  2.22  Pupils' ability to isolate and control variables The procedures of classification, hypothesizing, sorting out relevant  material from experiments, analyzing data, etc. involve not only conceptual understanding but use cognitive processes (Imenda,  1984).  These processes may provide the framework for a set of ideas or rules that can be used to interpret and explain data obtained in a given situation.  According to Piaget the highest cognitive process - formal  operations - allows reality to be c r i t i c a l l y examined from a sense of the many possibilities that i t contains. With formal operational capabilities, the pupil can handle complex problems consisting of three or more variables by controlling a l l but one of these variables and examining the influence of the uncontrolled variable.  Although Piaget's stages of cognitive development have come under close scrutiny and have not provided a panacea which some researchers had expected, some insight has been provided into pedogogical problems concerned with pupils' cognitive development. A relevant problem in  -29-  teaching science i s the c h i l d ' s a b i l i t y to c o n t r o l v a r i a b l e s ; t o keep a l l but one v a r i a b l e the same so the e f f e c t of one v a r i a b l e can be i n v e s t i g a t e d . According t o P i a g e t , as c o g n i t i v e maturity i s a t t a i n e d i n a v a r i e t y of concepts there i s a s h i f t i n the reasoning about r e a l or observed events t o reasoning about a l l the p o s s i b l e events i n a given situation.  The l e s s mature p u p i l i s l i m i t e d t o reasoning about the  s p e c i f i c content of the problem because he cannot generalize and apply an o r g a n i z a t i o n a l p r i n c i p l e learned about one v a r i a b l e (e.g. length) t o another v a r i a b l e (e.g. weight).  In contrast, c o g n i t i v e maturity brings  the c a p a b i l i t y of organizing any data, even v e r b a l l y presented information, by using generalized p r i n c i p l e s . The p u p i l can separate the i n d i v i d u a l v a r i a b l e s of the problem and consider the p o s s i b l e e f f e c t each v a r i a b l e might have. When the p u p i l reasons about these p o s s i b i l i t i e s , he i s not d e a l i n g with the objects themselves, but with t h e i r " t r u t h values". The p u p i l must therefore use p r o p o s i t i o n a l l o g i c .  In agreement with Inhelder and Piaget (1958), Treagust (1979) argued that p r o p o s i t i o n a l l o g i c i s a fundamental part of formal reasoning. Inhelder and Piaget have observed that the p u p i l who has obtained formal operations can use 16 operations of p r o p o s i t i o n a l l o g i c .  Of these 16  operations the b i c o n d i t i o n a l ( i f and only i f ) i s used i n s c i e n t i f i c hypothesis t e s t i n g . The reasoning behind hypothesis t e s t i n g would seem to require that an i n d i v i d u a l knows what i s expected assuming the hypothesis i s true.  Lamb and Betkouski (1980) suggest that once one knows t h i s then  he i s i n a p o s i t i o n to compare the expectations w i t h a c t u a l r e s u l t s . P r o b a b i l i s t i c and p r o p o r t i o n a l reasoning should develop only a f t e r b i c o n d i t i o n a l reasoning as they involve more complex operations such as  -30-  mentally formed r e l a t i o n s h i p s and comparisons.  The a b i l i t y t o form  r e l a t i o n s h i p s and comparisons i s p r o p o s i t i o n a l l o g i c and i s e s s e n t i a l f o r the  success i n the s k i l l of c o n t r o l l i n g v a r i a b l e s . However, Ennis (1975),  i n an a n a l y s i s of Piaget's schema, showed that the a b i l i t y t o "handle p r o p o s i t i o n a l l o g i c " i n Piaget's terms does not d i f f e r e n t i a t e young c h i l d r e n from adolescents.  Some of the complex operations are used  c o r r e c t l y by seven and eight year olds, others are used poorly by adolescents.  Ennis concludes "there appears t o be no connection between  i s o l a t i n g v a r i a b l e s and possessing the combinatorial system".  Further  support f o r the inadequacy of the 16 operations i n e x p l a i n i n g formal operations comes from Osherson (1974).  Using a s e r i e s of r e l a t e d  l o g i c a l problems the research attempted t o p r e d i c t success and f a i l u r e based on which operations were needed t o solve each problem.  He found  t h i s approach inadequate f o r p r e d i c t i n g patterns o f success i n i n d i v i d u a l subjects.  I t i s possible that the concept of a c o n t r o l l e d experiment develops e a r l y i n what Piaget c a l l s the concrete stage of development w i t h the idea of a f a i r comparison.  Fairness i s an e s s e n t i a l concept required i n the  c o n t r o l of v a r i a b l e s . Wollman (1977a) found that students remain unaware of general c r i t e r i a of f a i r n e s s even when they are capable of c o r r e c t l y judging a v a r i e t y o f comparisons as f a i r or u n f a i r .  Also l a c k i n g was a  c l e a r idea of how t o e x p l a i n or determine the causes of an event. Students were found not t o analyze the event i n terms of a complete s e t of v a r i a b l e s . Even when these a r e s p e c i f i e d , they do not then s y s t e m a t i c a l l y determine the r o l e s o f the v a r i a b l e s by varying them one a t a time. Piaget's formal stage i s supposed t o remedy t h i s s i t u a t i o n and development  -31-  seems to take place along systematic l i n e s .  In a school based p r o j e c t Kamm (1971) concluded that a programme on microbes appeared not to have f u l f i l l e d i t s secondary aim of teaching p u p i l s how to i s o l a t e v a r i a b l e s and the need f o r c o n t r o l s i n s c i e n t i f i c investigations.  This study concluded that c h i l d r e n automatically and  p r o g r e s s i v e l y a t t a i n the a b i l i t y to i s o l a t e v a r i a b l e s as t h e i r mental ages increase and that t h i s i s not a process that can be speeded up since i n " t r a i n i n g " i t was found that t r a n s f e r of reasoning from one p a r t i c u l a r problem to another was  Key ideas presented  slight.  i n other research (Wollman, 1977a, 1977b)  suggests that 1) even very young c h i l d r e n have acceptable s t r a t e g i e s f o r s o l v i n g some c o n t r o l l i n g v a r i a b l e s tasks and 2) a p r i n c i p a l dimension of d i f f i c u l t y may be the amount of information simultaneously  i n demand.  Based on a method of task a n a l y s i s devised by Pascal-Leone (1970), Case (1974) obtained evidence supporting the contention t h a t on the c o n t r o l l i n g v a r i a b l e s task the s p e c i f i c performance may processing information.  be l i m i t e d by the capacity for  Case (1974) conducted a t r a i n i n g study i n which  the separation of v a r i a b l e s procedure was taught to seven and eight year olds.  Responsiveness to t r a i n i n g was r e l a t e d t o the match between  a t t e n t i o n demands of the i n s t r u c t i o n a l method and the working memory and a t t e n t i o n capacity of the subjects.  Case's subjects d e a l t with three  informational items or three schemes at the same time.  A s i m i l a r set of  items f o r t h i s study could be: 1) Why 2)  does b a c t e r i a grow on X-1  p l a t e s ? (X = the t o t a l number of p l a t e s )  I t could grow because the a i r l e t i n has b a c t e r i a  -32-  3)  I t could grow because the agar wasn't s t e r i l e .  Case (1974) found that pupils,whose working memory was only capable of dealing with two items at the same time f a i l e d t o p r o f i t from the i n s t r u c t i o n a l procedure.  The next phase of the t r a i n i n g programme was  followed by those p u p i l s successful i n dealing with the three items.  information  These p u p i l s l e a r n t to deal with an added information item.  For  example, 1)  Why  does b a c t e r i a grow on X-1  plates?  2)  I t could grow because a i r l e t i n had b a c t e r i a  3)  or the agar wasn't s t e r i l e  4)  I f the agar was the same; i t can't be the agar.  When demands d i d not exceed capacity, t r a i n i n g was very s u c c e s s f u l , otherwise i t was not. Case's methods d e a l t w i t h "chunking" of items and making new  items s a l i e n t .  taking account of t h i s .  New  information  The subject becomes accustomed t o  ideas, new schemes are introduced simply i n  the context of a f a m i l i a r background. This necessitates that the tasks to be taught must be c a r e f u l l y analyzed. The learner's i n i t i a l knowledge l e v e l needs to be ascertained and l e a r n i n g a c t i v i t i e s l o g i c a l l y presented t o b r i n g the l e a r n e r from h i s i n i t i a l s t a t e to the desired s t a t e . At each step i n the l e a r n i n g process care i s taken to minimize the load on working memory.  information  Case's approach d i f f e r s from that of most  Piagetian influenced education researchers since there i s no attempt t o c l a s s i f y learners as concrete or formal.  Instead, Case's developmental  approach "advocates assessment of the learner's i n i t i a l state i n terms of the strategy which he a p p l i e s to the c r i t e r i o n task spontaneously" (Case, 1974).  -33-  Two important features of Case's (1974) work are that the information i s "chunked" to make salient items and that any new information i s absorbed into a familiar background.  Case believes that the ability to  control variables may be context dependent.  Therefore, i t i s important  that teachers at least ensure that pupils understand the basic variables presented in the context before expecting them to apply a general strategy of controlling variables.  Understanding the basic variables in the  context of this study would require the pupil to understand the living nature of bacteria, their distribution in the air and equipment, and the concept of sterilization.  -34-  2.23  The demands of p u p i l s  1  work i n the science classroom  The d i f f e r e n c e s between s c i e n t i s t s ' science, school teachers' science and school p u p i l s ' science ( G i l b e r t , Osborne and Fensham, 1982) create dilemmas which require addressing i f progress i n science education, i n the area of concept a c q u i s i t i o n , i s t o be achieved.  For many p u p i l s school  science i s an obscure a c t i v i t y f u l l of statements which are d i f f i c u l t t o make meaningful and worthwhile (Watts and G i l b e r t , 1983).  Teachers attempt t o promote conceptual change i n t h e i r classrooms toward more c o r r e c t s c i e n t i f i c views. Much c u r r e n t research i n t o how  this  process can be achieved has been based on an epistemological framework derived from recent development i n the philosophy of science often l a b e l l e d the "conceptual change" viewpoint (Kuhn, 1970; Toulmin, Lakatos and Musgrave, 1970).  1972;  The conceptual change b e l i e f can be  summarized as f o l l o w s : 1)  I n d i v i d u a l s approach any i n q u i r y with t h e i r i n d i v i d u a l p r i o r conceptions,  2)  The nature of these conceptions s i g n i f i c a n t l y determines the nature and the products of i n q u i r y ,  3)  I n q u i r y , rather than being an accumulation of f a c t s , i s the transformation of current knowledge, and  4)  R a t i o n a l i t y c o n s i s t s i n viewing new problems, ideas, and p r a c t i c e s against a backround of accepted conceptions and b e l i e f s ( i . e . against a t r a d i t i o n or heritage)  (Posner, 1982, p.  107).  C h i l d r e n have been encouraged t o change t h e i r concepts by i n t e r a c t i n g  -35-  with t h e i r environment.  Laboratory work appears t o be a perfect  opportunity f o r c r e a t i n g conceptual change.  However, when attempts have  been made t o measure the l e a r n i n g t a k i n g place f o l l o w i n g p r a c t i c a l work, a rather p e s s i m i s t i c p i c t u r e emerges (Johnson and McCallum, 1972; Johnstone and Wood, 1977; Gunning, 1978; Solomon, 1980).  Tasker (1981) i s not  surprised that science teaching i s not as e f f e c t i v e as we might have thought.  He found that i n many science classrooms  1) p u p i l s tend t o consider each lesson as an i s o l a t e d event w h i l e the teacher assumed that the p u p i l s appreciated the connecting l i n k between the lesson and the previous l e a r n i n g experiences, 2) p u p i l s sometimes invented a purpose f o r the l e s s o n which was subtly but s i g n i f i c a n t l y d i f f e r e n t from the purpose intended by the teacher, 3) p u p i l s often showed l i t t l e i n t e r e s t i n , or concern about those features of an i n v e s t i g a t i o n which the teacher, or textbook w r i t e r , considered t o be c r i t i c a l s c i e n t i f i c design features, 4) p u p i l s ' knowledge s t r u c t u r e s , against which l e a r n i n g experiences were considered, were frequently not the s t r u c t u r e s the teacher assumed p u p i l s had, and 5) p u p i l s ' understandings, developed from the outcomes of experimental work, were frequently not those that the teacher assumed were developed. Tasker (1981) a l s o found that p u p i l s are more concerned w i t h deciding what t o do next i n science experiments than i n considering s c i e n t i f i c concepts. Taskeer's (1981) view of p u p i l p r a c t i c a l work i s supported by Johnstone and Wham (1982).  P u p i l concern with the p h y s i c a l tasks o f the experiment  may be the r e s u l t of assessment procedures rewarding w e l l - w r i t t e n laboratory accounts, but omitting c r e d i t f o r p u p i l s ' statements about how  -36-  they r e a l l y view the procedures.  Being c r i t i c a l about the  students'  "recipe type" approach may be u n f a i r since t h i s may be the i n e v i t a b l e r e s u l t of the way  i n which p r a c t i c a l work i s frequently presented  organized by laboratory texts and curriculum guides. point of view the m a t e r i a l may organized.  seem to be w e l l explained and  To the l e a r n e r , the s i t u a t i o n may  incoming information may  From the  and  teacher's  coherently  look very d i f f e r e n t .  The  have no apparent meaning as p u p i l s could l a c k the  conceptual s t r u c t u r e to i n t e r p r e t t h i s new  information.  Freyberg  and  Osborne (1981) point out that c h i l d r e n often m i s i n t e r p r e t the ideas that they are taught i f they c o n f l i c t with t h e i r own personal views.  The  w i l l i n g n e s s to construct meaning and t e s t these against experience  and  s t r u c t u r e s i n long term memory i s c r i t i c a l i n terms of developing learner-generated meanings.  P u p i l s have to be motivated to construct  new  meaning f o r concepts since t h i s often requires much mental e f f o r t . Motivation depends on i n d i v i d u a l s accepting a major r e s p o n s i b i l i t y for t h e i r own l e a r n i n g (Wittrock and Lumsdaine, 1977).  P u p i l s often view p r a c t i c a l work as an i n t e l l e c t u a l non event.  "The  teacher asks, ' I wonder i f something w i l l happen when we add A to B?'; p u p i l thinks ' i f nothing was going to happen, he wouldn't be doing i t . Anyway he w i l l t e l l us the answer at the end even i f the experiment doesn't work!'" (Johnstone and Wham, 1982).  Postman and Weingartner  (1971) suggested that unless p u p i l s perceive a problem to be a problem and what i s to be learned to be worth l e a r n i n g , they w i l l not become a c t i v e and committed i n t h e i r s t u d i e s .  the  -37-  Another working hypothesis that has been advanced (Johnstone and K e l l e t t , 1980; Johnstone, 1980) i s t h a t l e a r n i n g i s severely hampered i n a high information s i t u a t i o n i n which the working memory i s overloaded incoming data.  with  The term working memory i s used t o describe the area of  memory that i s s o r t i n g and processing information i n t o short term or long term memory. Posner (1982) a l s o t a l k s o f a "problem space" and the f a c i l i t y of memory t o create t h i s space.  "In many problems, s e t t i n g up  the problem space leads t o the establishment achieved" (Posner, 1982).  of one or more goals t o be  Planning takes place next and subgoals are  determined and a p r i o r i t y system decides which subgoal i s worked on f i r s t (Greeno, 1977).  The problem solver thus plans work on a subgoal using  previous experience w i t h s i m i l a r problems and h i s framework of the concept as an a i d . The mental a c t i v i t y that p u p i l s engage i n t o construct meaning and t e s t constructions against sensed experience and s t r u c t u r e s i n long term memory are the r e s u l t of motivation.  Motivation i s c l o s e l y t i e d t o  i n t e n t i o n s , plans and previous experience and r e l f e c t s more than momentary environmental s t i m u l a t i o n .  A t t e n t i o n t o the p r a c t i c a l task i s influenced  by aspects of long term memory and c o g n i t i v e processes. A t t e n t i o n becomes s e l e c t i v e due t o these past experiences and therefore r e s u l t s i n s e l e c t i v e perception.  A t t e n t i o n involves both attending t o the unexpected and a  sustained i n t e r e s t i n the experience and requires v o l u n t a r i l y c o n t r o l l e d e f f o r t (Wittrock, 1981).  In order t o construct meaning from the sensory information provided by the experiment, l i n k s need t o be generated t o perceived relevant information i n the long term memory.  In the event that l i n k s are not  generated between new information and information i n long term memory the  -38-  l e a r n e r i s r e q u i r e d t o employ a l t e r n a t i v e s t r a t e g i e s ( C o l l i n s , Brown L a r k i n , 1980).  and  These i n c l u d e :  1) r e c o n s i d e r i n g t e n t a t i v e l i n k s and  attempting to l i n k a l t e r n a t i v e  a s p e c t s o f memory s t o r e t o the sensory  information,  2) c o n s i d e r i n g the p o s s i b i l i t y t h a t unfounded assumptions were used as a b a s i s f o r a t t e n t i o n and  s e l e c t i v e perception,  3) a t t e m p t i n g t o l i n k d i f f e r e n t a s p e c t s o f the sensory i n f o r m a t i o n memory s t o r e , 4)  to  and  s y s t e m a t i c a l l y considering a l l p o s s i b l e l i n k s to d i f f e r e n t aspects of l o n g term memory i n an attempt t o c o n s t r u c t meaning.  I t i s conceivable,  however, t h a t these a l t e r n a t i v e s t r a t e g i e s c o u l d  y i e l d d i f f e r e n t views o f the phenomena b e i n g  studied.  p l a u s i b l e , as some have suggested, t h a t c h i l d r e n and  Although i t may scientists  meaning i n b a s i c a l l y s i m i l a r ways from t h e i r e x p e r i e n c e s , c h i l d r e n generate are o f t e n very  d i f f e r e n t t o those o f  be  construct  the views  scientists.  Osborne, B e l l and G i l b e r t (1982) suggest a number o f p o s s i b l e reasons f o r this: a)  C h i l d r e n tend t o view t h i n g s from a s e l f - c e n t r e d or human-centred p o i n t o f view and  tend t o c o n s i d e r  that follow d i r e c t l y b)  from everyday  only  those e n t i t i e s and  constructs  experiences,  C h i l d r e n ' s e x p e r i e n c e s o f the w o r l d a r e l i m i t e d and  tend not  to  include contrived experimental s i t u a t i o n s , c)  C h i l d r e n tend t o be  i n t e r e s t e d i n p a r t i c u l a r explanations  s p e c i f i c events and  tend not t o be concerned w i t h the need t o have  m u t u a l l y coherent and phenomena,  and  non  contradictory explanations  for  for a variety of  -39-  d)  The everyday use of language tends t o be subtly d i f f e r e n t from the language of science, p a r t i c u l a r l y with regard t o basic and  important  words, l i k e "animal", " f r i c t i o n " , and "force", and these everyday meanings tend t o shape c h i l d r e n ' s constructions.  Research conducted t o date suggests that c h i l d r e n ' s ideas r e l a t e d t o science concepts can remain unaltered since science teaching has not encouraged conceptual change. change t h e i r conceptions.  Children may have no r e a l motivation t o  Symington (1981) found that c h i l d r e n who  could  provide t h e i r own reasoning f o r an everyday phenomenon tended not t o be i n t e r e s t e d i n what other p u p i l s had t o contribute as an explanation of that phenomenon - they already had an explanation that was p e r f e c t l y s a t i s f a c t o r y to them.  An understanding  of some aspects of current  s c i e n t i f i c thought would seem t o require a major r e s t r u c t u r i n g of c h i l d r e n ' s e a r l i e r ideas.  The student may choose to see a personal model  as i n v a l i d and replace i t with another model which could be that of the teacher or a f e l l o w student.  Sometimes the change i f f a r from that  envisaged by the teacher. Examples can be found where o l d e r c h i l d r e n have ideas which appear l e s s congruent w i t h the views of s c i e n t i s t s than the views of younger c h i l d r e n (Osborne, 1981; B e l l , 1981; Gunstone and White, 1981).  Tasker's (1981) f i n d i n g s concerning classroom experiences implied: 1) meanings are frequently generated by p u p i l s which are s u b s t a n t i a l l y d i f f e r e n t to those hoped f o r by teacher, textbook w r i t e r , or curriculum developer, 2) lessons are not l i n k e d by p u p i l s t o the appropriate knowledge from  -40-  previous lessons, 3) p u p i l s generate a purpose f o r a l e a r n i n g a c t i v i t y which i s d i f f e r e n t t o the teacher's intended purpose, 4) i n s u f f i c i e n t l i n k s are made, or are able t o be made, t o s c i e n t i f i c patterns of thought i n memory t o ensure that f u l l consideration i s given t o the c r i t i c a l design features of the experiment, and 5) the knowledge structures i n long term memory used t o generate meaning from a l e a r n i n g experience are sometimes inadequate, or inappropriate, and t h i s leads t o non s c i e n t i f i c outcomes. Freyberg and Osborne (1981) i n d i c a t e that i t i s easy f o r p u p i l s t o make l i n k s t o inappropriate aspects of knowledge i n long term memory.  Much of  science p r a c t i c a l work does not encourage the p u p i l t o f i n d l i n k s between knowledge i n long term memory and incoming information, or t o construct meaning and evaluate t h i s meaning against t h e i r own experiences.  Teachers are u n l i k e l y t o view laboratory work as obscure, meaningless, i s o l a t e d events since they are able t o construct meaningful l i n k s between the knowledge s t r u c t u r e s provided by the previous lesson and those concepts that are t o be presented i n the next lesson.  I t i s more  probable that teachers have considered the problems caused by d e t a i l e d laboratory work and the amount of information that p u p i l s have t o deal with i n the form of w r i t t e n i n s t r u c t i o n s , verbal i n s t r u c t i o n s , r e c a l l of manipulative s k i l l s , e t c . More thought needs t o be applied by teachers i n the area of l i n k i n g the incoming information t o knowledge structures held by the p u p i l .  This necessitates teachers knowing the substantive b e l i e f s  o f the c l a s s and how the p u p i l s are going t o view the l a b o r a t o r y event and use the incoming information.  -41-  2.3  Educational i m p l i c a t i o n s The b e l i e f s that p u p i l s b r i n g t o the science laboratory are often a t  variance with those that teachers wish them t o hold.  A transformation of  these a l t e r n a t e viewpoints i n t o viewpoints more acceptable t o the science teacher often requires accomodation of new information. This change of viewpoint can be achieved using i n s t r u c t i o n a l s t r a t e g i e s t h a t promote c o n f l i c t with the p u p i l s ' b e l i e f s .  Laboratory work i s often used by  teachers t o promote concept l e a r n i n g , but as we have seen (Section 2.2), t h i s i s not always successful since p r a c t i c a l s are often viewed as i s o l a t e d events and l i n k s between the concepts they should provide and theory work are often not formed.  P u p i l s often do not know how t o solve  some of the problems i n experiments due t o t h i s poor l i n k i n g o f concepts or t h e i r l a c k of knowledge s t r u c t u r e s . E x i s t i n g personal frameworks can therefore have a great influence on concept l e a r n i n g .  Preconceptions, a l t e r n a t i v e frameworks or c h i l d r e n ' s science are a l l terms r e f e r r i n g t o a person's e x i s t i n g conceptual framework.  They "are  amazingly tenacious and r e s i s t a n t t o e x t i n c t i o n " (Ausubel e t a l . , 1978) and can often i n t e r f e r e w i t h intended l e a r n i n g outcomes.  The student may  understand new information d i f f e r e n t l y from what was intended.  This new  information may w e l l take be a s s i m i l a t e d i n t o the p u p i l ' s own framework but continue t o be at variance with accepted s c i e n t i f i c conceptions.  Teaching attempts t o promote accomodation t o new concepts.  The term  "accomodation" i s taken from Piaget's (1964) theory t o denote what happens i n the student's mind as he modifies h i s preconceptions t o reach consonance with the perceived data.  Accomodation, then, requires  -42-  r e c o g n i t i o n by the l e a r n e r of d i f f e r e n t views of concepts which cannot be r e a d i l y accepted w i t h t h e i r e x i s t i n g conceptions.  According t o Hewson (1980), i f c h i l d r e n are to change t h e i r views they must f i r s t f i n d t h e i r present conceptions u n s a t i s f a c t o r y i n some way. I t seems that d i s s a t i s f a c t i o n with a present view i s not an important enough reason f o r the p u p i l to change viewpoints.  Children need an  a l t e r n a t i v e idea to replace the present view and t h i s i s required to be 1) i n t e l l i g i b l e i n that i t appears coherent and i n t e r n a l l y c o n s i s t e n t , 2) p l a u s i b l e i n that i t i s r e c o n c i l a b l e with other aspects of the c h i l d ' s view, and 3) f r u i t f u l i n that i t i s preferable t o the old viewpoint on the grounds of perceived harmony and usefulness (Hewson, 1980). Any change i n viewpoint may be a slow process since often s c i e n t i s t s ' views may appear to the pupil t o be l e s s i n t e l l i g i b l e , p l a u s i b l e , and f r u i t f u l than the p u p i l ' s own view (Osborne, B e l l , and G i l b e r t , 1982). The l e s s i n t e l l i g i b l e , p l a u s i b l e and f r u i t f u l view does not provide the motivation to generate the e f f o r t needed t o construct meaning from new views and l i n k them with ideas i n memory that w i l l develop a u s e f u l and sound understanding.  P u p i l s need t o f e e l that generating new meaning i s  worthwhile and s u c c e s s f u l . Often what i s required i n the l e a r n i n g of science i s the r e s t r u c t u r i n g of e x i s t i n g ideas so that p u p i l s see things from a d i f f e r e n t framework.  This personal r e s t r u c t u r i n g has been  l i k e n e d t o Kuhn's (1970) d e s c r i p t i o n of a major paradigm s h i f t (Walters and B o l d t , 1970). This may be achieved by showing p u p i l s the inadequacies i n t h e i r present conception and p r o v i d i n g them with l i n k a g e s and a l t e r n a t i v e frameworks which w i l l help toward generating new and u s e f u l  -43-  ideas.  New frameworks can s i m p l i f y r e a l i t y although they do not capture  a l l that i s going on.  2.31  Instructional strategies I t i s important that the teacher understands both the s c i e n t i s t s '  views and c h i l d r e n ' s views of a science concept. The teacher also needs t o be able to assess whether or not a c e r t a i n conceptual change i s a reasonable teaching goal with a s p e c i f i c group of p u p i l s .  Tasks need t o  be provided so that a p u p i l may c l a r i f y t h e i r own view about the p a r t i c u l a r phenomenon under d i s c u s s i o n .  P u p i l s need the opportunity t o  debate the pros and cons of t h e i r e x i s t i n g frameworks w i t h each other (Nussbaum and Novick, 1982). Nussbaum and Novick (1982) view the f i r s t phase i n an i n s t r u c t i o n a l strategy f o r f a c i l i t a t i n g accomodation should be that of making every student aware of his/her own preconceptions.  They  suggest an "exposing event", a s i t u a t i o n that evokes the student's own preconceptions.  The "exposing event" should " n a t u r a l l y i n v i t e a student  to e x p l a i n i t i n terms of h i s own preconceptions". E x p l i c a t i o n of p u p i l s ' preconceptions i n v o l v e s developing an atmosphere which enables students t o make e x p l i c i t t h e i r own frameworks.  Their productions might be verbal  using c l a s s or small group techniques ( G i l b e r t and Osborne, 1980; Nussbaum and Novick, 1981), i n w r i t t e n from (Watts and Z y l b e r s z t a j n , 1981), presented g r a p h i c a l l y (Pope, 1981), or some combination of these. should be encouraged t o state t h e i r ideas c l e a r l y and c o n c i s e l y .  Pupils This  process encourages a t t e n t i o n (Osborne and Wittrock, 1983) i n that p u p i l s are aroused t o defend t h e i r own ideas and concentrate on relevant issues. The l e a r n i n g environment i n which d i s c u s s i o n takes place needs t o be supportive and a p p r e c i a t i v e of the r i s k p u p i l s take i n d i s c l o s i n g personal  -44-  ideas.  Where the s c i e n t i s t ' s view o f a concept i s not represented i t may  be appropriate f o r the teacher t o introduce the s c i e n t i f i c viewpoint as an a l t e r n a t i v e view. For the s c i e n t i f i c view t o be considered s e r i o u s l y i t needs t o be introduced i n a way which takes i n t o account the views p u p i l s c u r r e n t l y hold.  2.32  Laboratory work I f teachers examine the presentation o f laboratory work they f i n d  methods that can be improved so as t o a i d the p u p i l s ' l i n k i n g o f concepts w i t h new conceptual information. When we develop a general concept i n lessons we often begin with a s i n g l e idea and 'elaborate' i t with examples.  For p r a c t i c a l work i t seems that the reverse occurs - complex  and numerous s t a r t i n g points lead t o or obscure the main point we t r y to make. To reduce t h i s problem we could adopt three ground r u l e s : 1)  Give a c l e a r statement o f the point o f the  experiment,  2)  State c l e a r l y what i s p r e l i m i n a r y , p e r i p h e r a l , and preparatory,  3) Avoid p o s s i b l e overload o f i n f o r m a t i o n by t r y i n g t o teach manipulative or i n t e r p r e t i v e s k i l l s a t the same time as data i s being obtained. Lawson (1983) suggests that without e s t a b l i s h i n g a d i r e c t connection between hypothesis and experimental r e s u l t s , v i a p r e d i c t i o n s already based on e x p l i c i t l y stated hypotheses, the f o r c e o f s c i e n t i f i c experimentation as a means o f generating knowledge i s weakened. a l l experiments  I t i s recommended that  should be conducted and reported w i t h not only a statement  of hypotheses t e s t e d and r e s u l t s obtained, but with p r e d i c t i o n s generated as w e l l .  During the experiment the p u p i l can experience d i f f i c u l t y  r e l a t i n g t o the main point of the experiment  and the relevance of incoming  sensory i n f o r m a t i o n . When the p u p i l can "chunk" incoming i n f o r m a t i o n some  -45-  of i t can be declared redundant and other preliminary and preparative work, such as labelling equipment and drawing tables for data, can be separated and organized accordingly.  A variety of visual representations  of information may enable the learner to process the information in the way he finds more appropriate.  Instructional material may be used to provide retrieval cues so that appropriate meaning i s generated from the material. Teachers could provide advanced organizers and questions to direct thought with the student clarifying thought through summaries, perhaps pictorally (Buzan, 1974) e.g. in flow charts and alternative explanations.  Rigney and Lutz  (1976) found in chemistry that supplementary verbal description with graphic analogies resulted in better learning and more positive student attitudes than presenting only verbal descriptions. There i s an aim to increase attention so to influence an increase in the learner's voluntary control.  Written material may need carefully worded headings, sub  headings, and focus questions to clarify the intent of the lesson. Attention can be influenced by the questions teachers ask pupils or learners ask themselves.  Pupils can be taught to ask each other  questions or ask themselves questions (Fraze and Swartz, 1975). Pupils need to be encouraged to develop or be explicity taught strategies to direct their own  2.33  study.  Problem solving Osborne and Wittrock (1983) believe that pupils find difficulty in  beginning stages of solving a problem.  Pupils appear to be unable to  construct meaning from the problem statement or connect their constructed  -46-  meaning o f the problem t o t h e i r knowledge s t r u c t u r e s . to l a c k of linkages or inadequate knowledge s t r u c t u r e s .  This i s e i t h e r due Research i n t o  problem s o l v i n g does not appear t o have discovered a l l that i s going on i n the student's head.  I t seems that i t i s not very u s e f u l t o think o f  problem s o l v i n g as a " s i n g l e , uniform c a p a b i l i t y " and s t r a t e g i e s devised t o a t t a i n a general problem s o l v i n g s k i l l " i s p r a c t i c a l l y hopeless a t t h i s stage of our understanding" (Greeno, 1977, p. 17). appears t o be highly content s p e c i f i c .  Problem s o l v i n g  Michael Polanyi (1967) points out  that much of human knowledge i s " t a c i t " i n t h a t , under ordinary conditions, i t can be e x p l i c a t e d i n words.  Perhaps t h i s applies t o the  s k i l l s of problem s o l v i n g as L a r k i n (1979) explains: " i f these t a c i t processes remain unexplicated, then, t o help a beginner l e a r n , there i s l i t t l e one can do beyond providing examples and p r a c t i c e , and hoping that the beginner w i l l somehow 'pick up' these unspecified s k i l l s . But i f one can begin t o b u i l d e x p l i c i t models f o r formerly t a c i t processes then i t becomes possible t o teach these processes, e i t h e r d i r e c t l y or through appropriately selected p r a c t i c e and example. I n a d d i t i o n e x p l i c i t models f o r t a c i t processes can aid i n i d e n t i f y i n g and remedying e r r o r s i n the developing s k i l l s of l e a r n e r s . " I f we want t o improve problem s o l v i n g a b i l i t y i n schools we could begin by analyzing the kinds o f problems c h i l d r e n are asked t o solve.  E l k i n d (1972) takes the p o s i t i o n that i n s t r u c t i o n i n c o n t r o l l e d experimentation generally should not be introduced u n t i l adolescence. In contrast Lawson and Wollman (1976) suggest a very gradual i n t r o d u c t i o n and continued r e i n t r o d u c t i o n o f lessons i n v o l v i n g concrete materials and a c t i v i t i e s t o enable students t o make comparisons and judgements. Wollman (1977b) suggests that a v a r i e t y o f experiences providing s i t u a t i o n s t o develop a general procedure may be useful since research on memory confirms the p o s i t i v e value o f varying the contexts i n which an idea  -47-  appears.  Setting up a controlled experiment requires the organization of many parts into a coordinated whole. sufficient.  Understanding the separate parts i s not  Time i s required for integration of the parts.  Not only i s  time required (perhaps more time than we alot in class) but practice too. Teachers may be able to integrate the parts by organizing the practical experience so that probing questions and memory retrieval cues lead pupils to generate the kind of meaning we want them to generate.  To create the  basic notion of fairness students could be confronted by the question of the validity of their judgements (Wollman, 1977b). As a result i t i s hoped that pupils might retrieve ideas from long term memory in order to better understand and interpret this situation.  Knowledge of inappropriate  contexts which pupils are likely to retrieve for the construction of meaning i s also important.  Pupils' prior knowledge structures should be  built on where possible and not ignored.  Stevens and Collins (1980) point out that good teaching requires the teacher to investigate student understandings and their deeper meanings. The teacher requires some idea of the likely knowledge structures in order to build on and modify pupils' ideas but at the same time to be generally sensitive to and supportive of pupils' ideas and reasoning  processes.  -48-  CHAPTER THREE 3.0  Methods o f study  3.1  Introduction The recent p u b l i c a t i o n o f numerous research s t u d i e s , with t h e i r focus  on the l e a r n e r ' s c o g n i t i v e s t r u c t u r e , represent a major s h i f t i n the r o l e and status given t o the learner i n the educational process. By using q u a n t i t a t i v e or q u a l i t a t i v e methodologies many of the researchers have explored the organization of s c i e n t i f i c concepts i n semantic memory. Those using a q u a l i t a t i v e methodology i s s u i n g from the i n t e r p r e t i v e ethnographic paradigm have i n the past received heavy c r i t i c i s m concerning i t h e i r v a l i d i t y , u n g e n e r a l i z a b i l i t y and subjectiveness. describes such studies as ideographic.  Power (1976)  In these studies students'  conceptualizations are analyzed on t h e i r own accord without reference t o "an e x t e r n a l l y defined system" (Driver and Easley, 1978).  Clinical  interviews and case studies are often i n the ideographic t r a d i t i o n . Supporters o f ideographic studies have moved towards personal, f l e x i b l e , interview techniques (e.g. Pines, 1979; Pines e t a l . , 1978) with loose a n a l y t i c a l forms o f conversation used t o i d e n t i f y student perceptions and construct a conceptual inventory.  In contrast "nomothetic s t u d i e s " assess students' understanding " i n terms of the congruence of t h e i r responses with 'accepted' ideas" (Driver and Easley, 1978).  scientific  Since these methods are often  q u a n t i f i a b l e , Power (1976) sees them as a r e f l e c t i o n o f the a g r i c u l t u r a l - s c i e n t i f i c paradigm.  The nomothetical approach i s a l s o  -49-  c h a r a c t e r i s t i c of many researchers engaged i n mapping c o g n i t i v e s t r u c t u r e (e.g. Deese, 1965; Shavelson, 1974; Preece, 1976) using various forms of word a s s o c i a t i o n techniques.  Considerable disagreement e x i s t s over tine appropriateness of these two methodological stances. D i f f e r e n t researchers value and t r u s t the two approaches d i f f e r e n t l y and the pursuant of one tends t o r e j e c t the other. Debate concerning the two method types does not centre only on the r e l a t i v e advantages and disadvantages of q u a l i t a t i v e and q u a n t i t a t i v e methods but a l s o on the c l a s h of methodological paradigms. As R i s t (1977, p. 43) s t a t e s " U l t i m a t e l y , the issue i s not research s t r a t e g i e s per se. Rather the adherence t o one paradigm as opposed t o another predisposes one to view the world and the events w i t h i n i t i n profoundly d i f f e r i n g ways".  Or as Roberts (1982) suggests - research i s not a " d i r e c t  inspection on r e a l i t y " . constructions on r e a l i t y .  People have used d i f f e r e n t ways i n order to put I t has been argued that paradigmatic  c h a r a c t e r i z a t i o n s i n f l u e n c e constructions on r e a l t i y .  Pepper (1942)  believes that understanding the d i f f e r e n t approaches used i n i n t e r p r e t i n g r e a l i t y i s aided i f one d i s t i n g u i s h e s between the four "adequate" world hypotheses of formism, mechanism, contextual ism and organism. L i n k i n g the two "adequate" world hypotheses of contextualism and organism, which use q u a l i t a t i v e data, does not r e s o r t t o a r i g i d and f i x e d approach since the three a n a l y t i c a l devices Pepper uses t o describe and compare the world hypotheses provide d i f f e r e n t o r i e n t a t i o n s f o r research.  Paradigmatic  c h a r a c t e r i z a t i o n s , those of the q u a l i t a t i v e methodology being phenomenological,  i n d u c t i v e , h o l i s t i c , s u b j e c t i v e , process o r i e n t a t e d and  o f a s o c i a l a n t h r o p o l o g i c a l world view, are based on two assumptions (Cook  -50-  and Reichardt, 1 9 7 9 ) .  Firstly, i t i s assumed that a method type i s  irrevocably linked to a paradigm and secondly that the quantitative and qualitative paradigms are assumed to be rigid and fixed.  Cook and  Reichardt ( 1 9 7 9 ) argue that these points should not be assumed.  No  discipline i s entirely "pure" with respect to world hypotheses and the emphasis of the different hypotheses function when conducting research in the process of putting constructions on reality.  Broad research paradigms should not be the sole determinant of the choice of methods. The choice of research method should also depend on the demands of the research questions and the research situation at hand. Quantitative methods have been developed mostly for verification or confirming hypotheses whereas qualitative methods were purposely for the task of discovery and generating hypotheses.  developed  The emphasis of  evaluation research has shifted away from the verification of presumed effects toward the discovery and elucidation of possible underlying structures influencing educational outcomes. Much of this evaluative research relies on qualitative methods.  The conduct of research is essentially aimed at developing an argument. In quantitative research argument rules and principles test the sufficiency of the data.  Qualitative research i s appraised on a parallel  basis - the argument has to be made defensible. The rules and  conventions  that warrant our moves from data to conclusion can be termed "warrants" (Roberts, 1 9 8 2 ) . Establishing warrants appropriate for use in qualitative research has been problematical due to the complexity of the interaction which occurs in the events of Science Education.  However, Peters, Hirst,  -51-  S h e f f l e r and others have c l a r i f i e d what educational concepts mean i n an educational s i t u a t i o n while Stephen Toulmin's work helps with regard t o constructs such as discovery and i n q u i r y , which are used extensively i n science education.  The l i n k a g e that e x i s t s between paradigm and method can u s e f u l l y guide one's choice of research method, but the research s i t u a t i o n i s a l s o an important f a c t o r .  The s o c i a l s c i e n t i s t of the " a g r i c u l t u r a l  s c i e n t i f i c " school (Power, 1976) c r i t i c i z e s the ideographic t r a d i t i o n c l a i m i n g that groups or i n d i v i d u a l s studied only once with a t o t a l absence of c o n t r o l produce data of l i t t l e s c i e n t i f i c value (Campbell and Stanley, 1966).  However, Campbell has since r e v i s e d h i s p o s i t i o n and acknowledges  t h e i r usefulness i n educational research (Easley, 1977).  Although one of  the strongest arguments against these ideographic s t u d i e s i s t h e i r l a c k og g e n e r a l i z a b i l i t y , Cronbach (1975) suggests t h a t "we  reverse our p r i o r i t i e s  because the observor i s appraising p r a c t i c e i n i t s normal s e t t i n g and observing i t s e f f e c t s i n context".  3.11  Background to methods used i n the study Any research programme w i t h aims t o enhace teaching and l e a r n i n g i n  the classroom must have meaning and f i l l the needs of the involved practitioners.  Recognizing t h i s P a r l e t t and Hamilton (1977) and Stake  (1974) e s t a b l i s h e d classroom research with emphasis on what was going on i n the educational s e t t i n g where the needs of the p a r t i c i p a n t s are given prominences.  A f u r t h e r s h i f t has then been t o pay more a t t e n t i o n t o the  learner as the focus of the education process.  For the teacher to obtain useful insight into his pupils' present ideas, reliable techniques are required for both finding out about a person's conceptual structures and for representing them on paper. Several techniques have been used in attempts to probe the learner's structure of ideas: 1)  Clinical interviews with individual pupils (Pines et a l . ,  1978;  Lybeck, 1979; Erickson, 1979), 2) Word association or word sorting tasks (Preece, 1978;  Shavelson,  1974;  Schaefer, 1979), 3)  Learners writing definitions (Schaefer, 1979), and  4)  Bipolar dimensions using semantic differential tests (Osgood et a l . , 1957) or repertory grids (Kelly, 1955).  In Sutton's (1980) review of research techniques for probing the organization of a learner's prior knowledge, he pointed to the limitations of some of these techniques when i t comes to their use in the classroom as part of the science teacher's repertoire.  Although the word association  and word sorting tasks are quantifiable, there are problems with the infinite associations, randomness, and the lack of the nature of the relationship between words (Stewart, 1979). Writing definitions may prove too d i f f i c u l t for the pupils whilst selecting definitions, although quantifiable and easier, may thought.  s t i l l not provide the dynamic quality of  Using methods involving bipolar dimensions may not be useful in  the classroom due to their application d i f f i c u l t i e s and the s k i l l s required in analysis.  As Fensham et a l . (1981) point out, i f research procedures were to  -53-  become part of the regular pattern o f teaching and l e a r n i n g i n science classroom they would have t o meet a number of c r i t e r i a focussed on issues such as: 1) the amount o f i n s t r u c t i o n a l time required, 2) congruency with teacher  behaviour,  3) providing tasks w i t h i n the a b i l i t i e s of students and teachers, 4) teachers are able t o use i n t e l l e c t u a l s k i l l s and procedures i n v o l v e d i n data gathering and a n a l y s i s , 5) a n a l y s i s and data meeting the requirements of the teacher, and 6) l e a r n i n g w i l l be helped as a r e s u l t .  With many of the above c r i t e r i a i n mind and considering the teaching s i t u a t i o n the c l i n i c a l interview and other d e s c r i p t i v e ethnographic techniqes were used t o c o l l e c t some of the data f o r t h i s study.  These  techniques w i l l be described i n more d e t a i l i n the f o l l o w i n g two s e c t i o n s .  3.12  The c l i n i c a l interview The c l i n i c a l interview as used i n science education research i s  derived l a r g e l y from Piaget's (1929) work and has been used e x t e n s i v e l y t o f i n d c h i l d r e n ' s responses t o a v a r i e t y of p h y s i c a l phenomena.  The  interview has been defined as "a conversation d i r e c t e d t o a d e f i n i t e purpose other than s a t i s f a c t i o n i n the conversation i t s e l f " (Bingham e t a l . , 1959, p. 3 ) . The purpose i s f i x e d i n the i n v e s t i g a t o r ' s mind and i f care i s not taken may lead t o the " s i t u a t i o n of interviewer seeking information from interviewee, and a t the other (end) a troubled interviewee seeking help from the i n t e r v i e w e r " (Posner and Gertzog, 1982, p. 195).  -54-  The c l i n i c a l interviewer's goal is to ascertain the nature and extent of an individual's knowledge about a particular topic area by identifying the relevant conceptions held and the relationships among those concpetions. In order to do this questions are used to e l i c i t information and encourage the pupil to take the lead and talk more freely.  "The art  of questioning, does not confine i t s e l f to superficial observations, but aims at capturing what i s hidden behind the immediate appearance of things" (Piaget, 1926, pp. x i i i - x i v ) .  Pines et a l . (1978) have produced much work using c l i n i c a l interview techniques.  It i s pointed out that the researcher has to deal with two  aspects of the interview.  Pines sees these as being the inflexible and  flexible parts. The. inflexible parts are as follows: 1) establishing rapport, 2) setting the scene of the interview including the arrangement for recording, and 3) declaring of the content f i e l d by the researcher and i t s acknowledgement by the learner. The flexible part involves the interviewer's judgement as to how much to encourage pupils with unbiased 'I see', 'Go on', 'And so' statements before refocusing the learner on the original conception. E l i c i t i n g these original conceptions i s achieved by semi-structured question framework. This framework i s made up of questions that are general enough to be placed in a variety of places within the interview. The questions openended nature should encourage the child to respond freely in his own words therrefore revealing the nature of their perspective. If the answers are judged irrelevant the question may be asked again in another form (Pines  -55-  et a l . , 1978).  Conversations overcome the reluctance on the part of the  subjects t o respond f u l l y i n w r i t i n g t o questions.  However, there are  d i f f i c u l t i e s i n o b t a i n i n g q u a l i t a t i v e data using the interview.  The  interviewer has t o r e a l i z e the danger of allowing h i s preconceived ideas to lead t o suggestions that the student may take up, thereby o b t a i n i n g misleading data on the c h i l d ' s genuine ideas.  Nuances i n phrasing, a  p a r t i c u l a r word, or the s e l e c t i o n and ordering of queries can a l l stimulate suggested c o n v i c t i o n s .  A f t e r the interview, t r a n s c r i p t s are  made from the recorded interviews and these become the b a s i s f o r l a t e r analysis.  3.13  Classroom data The classroom teaching s i t u a t i o n has more p o t e n t i a l to d i s t o r t the  students' responses toward a more 'accepted' school view of the t o p i c area under c o n s i d e r a t i o n than the c l i n i c a l interview s e t t i n g .  This i s because  the classroom i s seen as an assessment environment. Hence classroom based research has always been faced with a number of d i f f i c u l t methodological problems regarding the v a l i d i t y of the data c o l l e c t e d .  Douglas Barnes  (1979) has suggested an approach that may a l l e v i a t e some of these d i f f i c u l t i e s and be more manageable to handle i n the classroom.  After  working w i t h d i f f e r e n t small groups of p u p i l s on a v a r i e t y of topics he concluded t h a t small group work allows discussion, recording of experiences w i t h speech being used t o communicate or r e f l e c t thoughts. Gagne and Smith (1962) have also indicated t h e i r support f o r student v e r b a l i z a t i o n f o r c l a r i f y i n g t h e i r ideas.  Barnes (1979) found that p u p i l s tend t o organize thoughts on a  -56-  c l e a r e r b a s i s f o r f e l l o w p u p i l s than they do f o r teachers.  This seems  dependent on the knowledge of the audience; the l e s s knowledge the audience i s expected t o have then the more e x p l i c i t the explanation.  He  also found that taped discussions o f c h i l d r e n working on t h e i r own on a problem that had been c l e a r l y defined produced t r a n s c r i p t s w i t h examples of "exploratory speeach".  The t a l k i n g out of problems, rearranging o f ,  ideas and t e n t a t i v e moves towards hypotheses were seen as relevant t o the pupil.  Occasionally the interviewer i n the c l i n i c a l s e t t i n g may perceive  something as i r r e l e v a n t whereas the student sees these ideas as important to h i s "framework".  Groupwork may be a safety net t o catch these ideas.  Once c h i l d r e n have become used t o e x p l a i n i n g t h e i r groupwork t o a tape recorder the "exploratory speech" may r e f l e c t more of the nature of the c h i l d r e n ' s ideas than would a more formal s e t t i n g , such as an i n t e r v i e w or a large c l a s s d i s c u s s i o n , which would normally produce a "formal" response.  I n many examples shown by Barnes and Todd (1975) the p u p i l s discussed questions posed on a task card.  The task had been c l e a r l y explained,  p u p i l s had been introduced t o the equipment and shown how t o operate i t . These researchers were anxious t o preserve i n t h e i r a n a l y s i s o f the r e s u l t i n g conversations the features of c h i l d r e n ' s t a l k that they viewed as t h e o r e t i c a l l y important, i . e . the construction of the p u p i l ' s own knowledge would be conserved.  This i s e s s e n t i a l since the s t r u c t u r i n g of  concepts i s thought t o be an ever changing, dynamic framework.  -57-  3.2  Methods of data collection The methods of data collection used in this study were selected  because they could be accomplished within a normal teaching situation. Pupils did not need to learn new s k i l l s and a learning situation was created by these methods.  Clinical interviews with individual pupils and transcripts from children's group work experiments have been used to identify the beliefs concerning bacteria and the interaction of these beliefs during experimental procedures.  Group work tapes have also been used, although  less rigorously, along with written work.  3.21  Data collection schedule The collection of data was organized to f i t into the normal school  timetable.  Science lessons were available within the time limitations of  the curriculum.  These consisted of one seventy minute lesson and, two  days later, one thirty-five minute lesson per week. It was also possible to use a thirty-five minute library period that ran concurrently to the single science period. When pupils were interviewed during this time they were provided with a word search task on "diseases" and after being interviewed they returned to the library.  The c l i n i c a l interview to obtain the pupils' beliefs concerning bacteria (interview one) took place prior to the introduction of the topic in the f i r s t half of the second school term. pupils.  This involved thirty-one  -58-  In the second half of the term the topic of "bacteria" was using the two experiments in the study.  introduced  Due to curriculum constraints a  maximum of three weeks was allowed for this topic so tasks and interviews were arranged for the two experiments within this time span.  Clinical  interview two involved nine individual pupils while two groups of four and three pupils respectively provided tapes of group work for the experiment •Bacteria in the Air*.  Clinical interview three involved another nine  pupils and two more groups of two and three pupils respectively were taped performing the experiment 'Bacteria on Ourselves'.  TABLE I  Summary of data gathering schedule for experiment one "Bacteria in the air it  Time  Class period 1  Task  set up experiment 'Bacteria in the a i r '  Data Gathering Method  small groups taped during experiment Group 1 A (4 pupils) Group 1 B (3 pupils)  Between class  Class period 2 group discussion of experiment  individual c l i n i c a l interviews (interview 2) (9 pupils)  small group discussions presentation of overhead materials laboratory write up centred on specific questions  -59-  TABLE II  Summary of data gathering schedule for experiment two "Bacteria on Ourselves" Class period 3  Task  set up experiment 'Bacteria on Ourselves'  Data Gathering Method  small groups taped during experiment Group 2 A (2 pupils) Group 2 B (3 pupils)  3.3  Between class  Time  Decription of the clinical  Class period 4 group discussion of experiment  individual clinical interviews (interview 3) (9 pupils)  small group discussions presentation of overhead materials laboratory write up centred on specific questions  interviews  Each pupil's ideas were recorded on tape for the f i r s t interview.  initial  Whilst every pupil willingly participated in the interviews,  the researcher f e l t that the goodwill of the pupils would be put to the test i f each pupil was interviewed for each experiment and timewise this was prohibitive.  Thus for both experiments one and two nine pupils were  interviewed.  Pupils were asked for permission to record their conversations. Each interview was intended to be as relaxing as possible and i t was stressed that in essence i t was a private interview and a non assessment situation. Each interview lasted approximately ten minutes. Clinical Interview One The purpose of this interview was to e l i c i t the pupils' beliefs about  -60-  bacteria. Pupils were interviewed prior to any school learning experience concerning bacteria.  The interview was structured around a series of  questions intended to e l i c i t student beliefs.  In this f i r s t set of  interviews the typical questions asked were: 1)  Have you ever been i l l ?  2)  What kind of things cause these illnesses?  3)  How do people catch these illnesses?  4)  Are bacteria/germs alive?  5)  How can you t e l l ?  6)  (If so) where would they live?  7)  What do bacteria/germs look like?  8)  Do you think a l l bacteria/germs are harmful?  Clinical Interview Two The purpose of this interview was to e l i c i t the understanding of the experiment and i t s results, 'Bacteria in the air' (Experiment 1).  The  class carried out the experiment in small groups after the researcher had explained the procedure and shown the petri dish and the agar to the class. Pupils were asked to think about the questions reproduced from the Combined Science text and answer these for homework.  A few days later, before the next lesson and after some growth had been achieved on the plates, nine pupils were interviewed.  The interview  was structured around the questions considered for homework but in a less formal manner. The following questions are typical of an interview at this stage:  -61-  1)  Why did we s t e r i l i z e the agar?  2)  How could we t e l l that there aren't any germs i n the j e l l y when we started?  3)  Why d i d we have clean hands a t the s t a r t of the experiment?  4)  Why d i d we have a p l a t e f o r a draughty place (plate 1) and a draughtless place ( p l a t e 2)?  5)  Why d i d we have t o open the dishes f o r so long?  C l i n i c a l Interview Three The purpose of t h i s interview was t o e l i c i t the understanding o f the experiment and i t s r e s u l t s , 'Bacteria on Ourselves'  (Experiment 2 ) .  The  whole c l a s s c a r r i e d out the experiment according t o i n s t r u c t i o n s reproduced from the Combined Science Text. small groups and afterwards the experiment.  Again the p u p i l s worked i n  considered questions concerning the method o f  These questions formed the basis o f the the t h i r d  c l i n i c a l i n t e r v i e w . Nine p u p i l s were interviewed; the f o l l o w i n g questions are t y p i c a l of an interview: 1)  Why do you t h i n k we had p l a t e s A and B?  2)  What do you expect t o see on these plates?  3)  I f there weren't b a c t e r i a on plate C what was the purpose of having p l a t e C?  4)  Does i t r e a l l y matter that a l l the p l a t e s were s t e r i l e a t the beginning of the experiment?  5)  3.31  Why d i d we put p l a t e s i n the incubator?  D e s c r i p t i o n of the taped small group discussions The taped small group discussions involved four groups of p u p i l s i n  -62-  total.  Two groups of pupils were selected for each experiment. Twelve  pupils were involved in this part of the project.  Each group was provided with a work sheet explaining the procedure for the experiment and a question sheet for the group to answer. The groups were shown how to use the tape recorder and asked to record their work as soon as they got to their desks.  Each group worked in a separate  room until they f e l t that they had set up the experiments and answered the questions satisfactorily. Small group work CIA and 1B) during class period 1 Pupils were selected so as to be representative of the class. For this experiment "Bacteria in the Air" group A consisted of four boys. Originally only three boys were in the group but a new boy came late to class and social considerations dictated that he joined this group. Group B consisted of three g i r l s .  The members of both groups were a l l used to  working with each other and were cooperative and able to work on their own with minimal supervision.  The pupils were also considered to be  sympathetic with the project and enjoyed taping their ideas.  The groups' task was set out on a printed sheet and they were asked to record the setting up of the experiment and discuss and answer six questions on an acetate overhead projector sheet (See Appendix E for a description of these instructions and questions). Small group work (2A and 2B) during class period 3 Two more groups were selected to participate in the taping of  -63-  experiment two "Bacteria on Ourselves".  Group A consisted of two g i r l s ;  their third member of the class being absent. three boys.  Group B was made up of  Again the group task was set out on a printed sheet, tape  recorders were provided along with equipment for the experiment.  After  setting up the experiment the pupils were asked to discuss their answers to seven questions and also record these answers on an overhead projector acetate (See Appendix E for a description of these instructions and questions). Other group work During class periods two and four the pupils worked in their original groups and a spokesperson for each group presented the group's ideas and answers to the questions answered in the previous lesson.  Each group  produced an overhead for this purpose.  3.32  Written work The written work produced was of two types, 1) as a result of group  discussion, or 2) write ups from laboratory experiments with questions. The questions used in each case were given to pupils for consideration as a group and for homework.  3.4  The subjects The subjects used in the study were of the same age group that the  curriculum developers of the Nuffield Combined Science Scheme had in mind when writing the section on microbes.  The pupils attend a secondary  modern school in a suburban environment. A l l of the class were considered  -64-  to be in the second quartile of the school population for IQ scores. The class consisted of thirty-one twelve/thirteen year olds who already had been taught Science as a group for one term by the researcher. This class was chosen for the research project since they were responsive and enthusiastic and i t was considered that they would benefit from the research approach taken. concerning microbes.  None of the pupils had had any formal teaching  In the f i r s t term a l l had learnt to use microscopes  and taught some basic concepts of cells.  Their f i r s t year curriculum  had included work on living things. A l l the members of the class were involved in the f i r s t c l i n i c a l interview.  In the second and third interviews approximately one third of  the class was used in each case. the third portion of the class. TABLE III  The schedule i s summarized below:  Number of pupils involved in interviews  c l i n i c a l interview number of pupils groupwork  Pupils selected for group work made up  -1st 31  2nd (1st experiment)  3rd (2nd experiment)  9  9  7  5  For the group work pupils were selected on their ability to work without help, in a group, with a willingness to discuss and listen to other pupil's views.  This was essential in order to obtain some sort of  interaction of ideas. The prior selection of these pupils l e f t two thirds of the class available for other interviews.  Interviews took place in a  normal school setting and they were used as a learning situation for the pupils.  -65-  3.5  Analysis of data  3.51  Introduction As already mentioned earlier in Section 3.12, various methods have  been used in the past to represent a subject's knowledge.  Deese (1965)  was among the f i r s t to investigate cognitive structure using word association tasks that provided quantifiable data which could be used to construct concept maps. Researchers (Deese, 1965; and Shavelson, 1974) interpreted the pattern of interconnections among associations as being a major aspect of cognitive structure.  Shavelson (1974) has stressed the  importance of examining an hypothesized structure or organization of concepts in a subject's memory and i t s possible relationship with subject matter.  He attempted to determine this hypothesized mental structure  using word association and represented these in diagraph form and spatial maps. These assessment techniques assumed that the response retrieval from long term memory reflects part of the structure within and between concepts. However, a major problem with associative mapping techniques i s that concepts learnt at the same time may only be associated in temporal terms.  The researcher needs to make sure that the assessment technique  does in fact test cognitive structure.  Sutton (1980) also has  reservations concerning mapping since this suggests a lack of fluidity in mental structure.  However, Preece (1978) suggests that concept maps only  describe the format of the data base.  In science learning the links  between concepts are precise propositional statements that have very definite meaning. Scientific concepts have a multiple of private meanings which change or extend their meanings.  Stewart (1979) argues that  associative mapping procedures do not allow this f l e x i b i l i t y .  -66-  The human inforaation processing view directs i t s efforts towards the development of theoretical models of how knowledge might be stored in a propositional format. Many different assessment techniques have been used to acquire information.  Of the many, c l i n i c a l interviews provide  researchers with the opportunity to gain insights into how people store and recall knowledge and use i t in thinking.  However, care should be  taken in the c l i n i c a l interview situation by the researcher to make sure that he/she i s pursuing the line of thought of the subject and not his/ her own.  During analysis of data derived from the c l i n i c a l interview there i s a danger in the possible misinterpretation  of responses.  Piaget suggests  that "the psychologist must in fact make up for the uncertainties in the method of interrogation by sharpening the subtleties of interpretation" (1929, P. 9 ) .  Rowell (1978) used c l i n i c a l interviewing as the principal technique for evaluating concept learning and evaluated each child's interview responses by categorizing his or her overall performance. The outcome was one response rating per child which characterized the degree of the child's use of models.  Movement toward characterizing a particular child  as a "modeler", "partial modeler" or "non modeler" has obscured the capability for describing the substantive qualities and interrelationships of the concepts being learnt.  According to Posner and Gertzog (1982),  Rowell failed to establish a useful or valid measure of concept learning.  Another study of science concept learning was carried out by Pines  -67-  (1977) using a modified Piagetian c l i n i c a l interview.  Pines disagreed  w i t h c a t e g o r i z i n g c h i l d r e n since they " e x h i b i t responses c h a r a c t e r i s t i c of many categories i r r e s p e c t i v e of the category system used" (1977, p. 192). In h i s a n a l y s i s he attempted t o reduce the interviewee's discourse t o manageable u n i t s while at the same time preserving i t s i n t e g r i t y .  This  system of "conceptual p r o p o s i t i o n a l a n a l y s i s " (CPA) was designed t o e l u c i d a t e "substantive content, i n d i c a t i n g c o g n i t i v e d i f f e r e n t i a t i o n and enabling the comparison o f discourse a n a l y s i s " (Pines, 1977, p. 74).  The  CPA process could a c t t o increase the danger of f a i l i n g t o recognize suggested c o n v i c t i o n s by i n c l u d i n g i n c h i l d r e n ' s responses phrases taken d i r e c t l y from the i n v e s t i g a t o r ' s questions.  Although the basic sense of  the discourse i s maintained, the o r i g i n s o f c e r t a i n concepts and a s s o c i a t i o n become unclear.  3.52  A n a l y s i s used i n the study As mentioned i n Section 2.21 the concept map i s a device' t o e x p l i c i t y  represent a number of concepts, they can a l s o be used t o determine the framework o f p u p i l b e l i e f s toward t h i s subject matter.  Concept maps have  a p p l i c a t i o n i n the teaching o f a l l sciences a t a l l l e v e l s and can provide the teacher with much valuable information. r e l a t i o n s among other concepts. r e l a t i o n s with other concepts.  A concept, then, i s a s e t of  The q u a l i t y of the concept i s due t o the The map i l l u s t r a t e s - t h e data base present  i n the p u p i l ' s long term memory (Preece, 1978) and the p r o p o s i t i o n a l r e l a t i o n s between the concepts a t that one p a r t i c u l a r time.  The terms i n  the boxes are concepts and the verb or l o g i c a l connective c o n s t i t u t e s a propostion.  "The nature of a person's understanding  o f a concept changes  as i t i s associated w i t h a wider array of concepts and s p e c i f i c  -68-  p r o p o s i t i o n s " (Malone and Dekkers, 1984).  Based on Ausubelian  (1978)  l e a r n i n g theory i t would be a n t i c i p a t e d that concept maps demonstrating meaningful l e a r n i n g would possess an organization o f concept d i f f e r e n t i a t i o n ranging from the most general, more i n c l u s i v e concepts a t the centre t o more s p e c i f i c and l e s s i n c l u s i v e concepts a t the perimeter. Examples of p u p i l s ' concept maps are shown i n Appendix A2.  P u p i l ' s p r o p o s i t i o n a l statements extracted d i r e c t l y from the f i r s t c l i n i c a l interview data were used i n the construction o f the concept map for  that p u p i l . Using these p r o p o s i t i o n a l statements, and with the a i d o f  the concept maps constructed from them, the substantive b e l i e f s held by the c l a s s concerning b a c t e r i a were obtained and summarized.  In order t o detect the b e l i e f s p u p i l s held concerning the two experiments being studied p r o p o s i t i o n a l statements supplied by the interviewed p u p i l s were again i s o l a t e d .  These were a l s o used t o compare  with the substantive b e l i e f s obtained from the f i r s t interviews i n order t o detect any general conceptual  change. I t was f e l t necessary t o e x t r a c t  statements from the interviews as close t o the o r i g i n a l p u p i l statements as possible since i t was thought e s s e n t i a l t o capture the subtle meanings of each statement.  Although concept maps were used i n the f i r s t  instance  t o i s o l a t e substantive b e l i e f s i t was thought that the p r o p o s i t i o n a l l i n k s between concepts provided i n the interview were not s t a t i c and showed s i g n s of f l e x i b i l t y that a concept map could not d i s p l a y . To lend support to interview data extracts from group work and w r i t t e n work were also used.  -69-  CHAPTER FOUR 4.0 Introduction This study has been conducted with the knowledge that the prior beliefs which pupils take into the science laboratory interplay with their understanding of the scientific processes of experiments, or as Finley (1983) suggests that the concepts "drive" the scientific processes. By this statement Finley means that the exact nature of science processes are dependent upon the conceptual knowledge that i s used to understand a particular phenomena. In order to examine the way in which pupils' beliefs concerning bacteria interact with their understanding of the experimental procedures involved in the two experiments studied, i t was, f i r s t l y , necessary to extract the substantive beliefs pupils held concerning bacteria from the f i r s t c l i n i c a l interview. As an aid to analysis, concept maps were constructed for the elicited beliefs obtained from individual pupils.  The next step  involved extracting pupils' viewpoints relating to specific aspects of the experimental setting from c l i n i c a l interviews two and three. The three c l i n i c a l interviews conducted provided data for the following research questions: 1)  What methods of identification of bacteria are used?  2)  Are bacteria viewed as living units and i f so, why?  3)  Is i t important to have sterile media and i f so, why?  4)  Is i t important to have, a control in the experiment and i f so, why?  5)  What i s the overall understanding of the experimental procedures elicited from the pupils?  -70-  This chapter presents answers to these research questions.  The material extracted from the transcripts i s true to the pupils' recorded speech.  The nature of this pupil speech is truncated and  hesitant and in many cases the sentence construction i s incomplete due to pupils reflecting on their argument and then starting a new line of thought.  Where appropriate, the missing words have been added in  parentheses to help the reader understand the text. The author views the original transcript material as an important data source since i t provides opportunity for closer inspection of the nature of the pupils' thinking. Written material provided by the pupil is not able to reveal the nature of pupils' thinking in such detail.  Due to the vast amount of data collected, i t was not feasible to reproduce a l l utterances made by the pupils. Selected parts of transcripts have been used in the following sections as illustrative material of substantive beliefs held by a number of pupils or of unique viewpoints held that are particularly interesting. Selected complete transcripts for a l l data gathering methods can be viewed in the appendices.  4.1  Pupils' substantive beliefs concerning bacteria The following substantive beliefs were obtained from transcripts of  the i n i t i a l c l i n i c a l interview.  This f i r s t interview involved thirty-one  pupils in the second year class (12-13 year olds) being taught by the interviewer at the time.  -71-  In the class of thirty-one pupils, eleven pupils provided spontaneous convictions that bacteria cause many diseases.  Thirteen pupils used the  word "germs" while three pupils used both germs and bacteria and indicated that the word germs was a general term that included bacteria. Two pupils used the word germs to include the group they knew as viruses. pupil used the colloquialism "bugs".  Only one  A l l , except one pupil, related the  belief that diseases were caused by bacteria, germs or "bugs". However, in the class there were ideas that environmental circumstances e.g. getting cold, cold weather and water, washing hair and going out would cause a cold.  Eight pupils concurred with these beliefs but only one  believed that personal habits and environmental factors as mentioned were the only causal agents of disease.  Bacteria or germs were considered small and could only be seen with the aid of a microscope (24 pupils) and they were small and light, usually floating in the air (10 pupils).  Nineteen pupils believed that diseases  were spread by breathing in these bacteria and germs either from someone else or from the air; of these, ten pupils identified sneezing or coughing as mechanisms that spread disease.  Fifteen pupils said that they thought  that different types of germs or bacteria cause different diseases.  In  the following exerpt, Sharon and Mark give their reasoning for this idea: Int: How Sharon: Int: How Sharon:  come there i s such a difference between colds? Types of germs. could you t e l l they were different types? They react to different parts of your body.  Int: Do you think there are lots of different types of germs around? Mark: Yes. Int: How do you know? (that there are different types of germs around) Mark: Because there are loads of diseases you catch. A different germ for every different disease.  -72-  Apart from bacteria or germs causing a variety of different ailments they were different in shape (8 pupils), size (4 pupils), and complexity of appearance (1 pupil).  A l l pupils with ideas about germs or bacteria  thought they were living although the reasoning behind this was not too coherent.  Only two pupils identified three activities of living  organisms, but they didn't use these as their reasons for bacteria being living as can be seen i n the following extract: Int: What makes you think they are living? Sharon: Because they form plaque in your teeth and .... Int: But you're always brushing away this plaque, don't these bacteria disappear? Sharon: Yes, but they must be alive because they come back a l l the time.  Sharon mentioned that bacteria can grow and become "bigger like families do, you know they were reproducing and that", and, in her words, also "eat cells".  However, these beliefs were not given as reasons for  the organism to be considered living.  Other pupils appear to be able to discuss the attributes of "living things" better than the characteristics of live microorganisms: Int: How do you know that they are living? Deborah; I don't know, (I) think they do. Int: What kind of things do "living things" do? Deborah: They eat. Int: So what would a virus eat? Deborah: Blood cells. Int: So they live i n the blood, do they? Deborah: Yes. Int: I f there i s only one virus in your body i t won't do you much harm will it? Deborah: No, they can multiply though. Int: How would you know that things are living or not? Mark: I f they move around they are probably living. Int: Are there any other reasons? Mark: They eat and drink.  -73-  Many students used other reasons not related to the normal characteristics attributed to living organisms.  For example:  Int: How would you know whether they (bacteria) were alive? Philip: Because they wouldn't know where to go else, would they - in your teeth and your throat and that. Int: How do you know they (bacteria) are living? CIive: They've got to be haven't they. Int: Well no - there are lots of things that are dead. Clive: Well i f they were dead they wouldn't be causing any illnesses because you get different germs inside you that k i l l them so you don't get the disease. Int: So how would you know that they (bacteria) were living? Justine: Because i f they weren't you wouldn't have the disease else and they would be dead and wouldn't be able to get inside you anyway. The belief that bacteria or germs were living because they caused a disease was held by five pupils.  There was a range of locations where one might find bacteria; in the air (ten pupils), in animals' bodies (nine pupils), everywhere (seven pupils), in the earth or dirt (three pupils), on skin (three pupils), in water (three pupils), in blood (two pupils), and in cold places (one pupil).  Only two pupils thought that bacteria required a living host.  There was a l o t of optimism that these bacteria could be killed and even might be useful when dead for making medicines or vaccinations. When alive good germs fight off bad germs and these same germs could also be used for testing against other germs.  Nine pupils mentioned that the  body had a defense system against such pathogens as bacteria and a few talked about immunity (two pupils), antibodies (one pupil) and antibiotics (one pupil).  -74-  In summary, many pupils had a wide range of beliefs concerning microorganisms that caused disease. Pupils expressed most of their information about bacteria through their beliefs of disease. A surprisingly high proportion of the class used the term bacteria whilst others were more familiar with the term "germ".  Both words were associated with organisms  that are small and living. However, l i f e concepts throughout the class were mostly unsupported by other concepts.  Bacteria and germs were  considered to be quite common organisms easily passed on through the a i r by people sneezing and coughing and they were often considered alive because they could cause disease. People often were thought to become i l l through contact with water and bacteria had some role to play in this belief.  It was reassuring to note that many of the pupils believed that  these bacteria caused short term illnesses and that the body had some mechanism of fighting disease.  Each pupil viewed the relationships between their concepts of bacteria/germs in a slightly different and unique way.  So as to provide  an overview of each pupil's beliefs and their relationship to one another a concept map was constructed from substantive beliefs taken from each pupil's f i r s t c l i n i c a l interview.  The linkages do not indicate the  strength of the relationship but simply that one exists and that this relationship was expressed by the pupil. Appendix A2 provides examples of this type of annotation of pupil responses.  4.11  Pupils' sources of information In the previous section the variety of substantive beliefs elicited  -75-  from the f i r s t c l i n i c a l interview were discussed without reference to the pupils' sources of information. From the multiformity of beliefs shown there could be a variety of information sources.  It i s to these sources  that this section i s addressed.  Pupil's vocabulary often reflects the nature of the source of information.  Television documentaries use the word bacteria rather than  germ and could influence the pupils to use the word bacteria. Three pupils related information that they obtained from watching television programs, but apart from programs pupils view advertisements that provide information regarding "germs" and hygiene. Some of the pupils who used the word bacteria had watched T.V. documentaries, one had even viewed the plating of cultures as the following excerpt shows: Mark: I watched a program on television where they got this jelly stuff and they smeared one, they smeared a mumps smear over i t and then they got something out of this bloke's body and smeared i t on top of i t to see what happened and a l l the germs from the mumps had split up into l i t t l e groups so the b i t that they put on top had spread out with i t and the mumps germs were sort of shrinking and getting smaller. These events have the potential for modifying frameworks or even in Lewis's case, extending them: Lewis: Int: Lewis:  Sometimes they've (doctors) got the dead disease and they inject into you so you can get white corpuscles and things like that to fight i t (bacteria). Where did you learn about white corpuscles? I watched a program on t e l l y .  Others had had discussions with respected authorities such as dentists. I t i s possible that dentists could influence pupils' conceptual frameworks by providing additional information about bacteria. This would be in addition to sources from television and books. An extract from  -76-  Philip's interview shows the concepts he gained from a v i s i t to the dentist: Int: What happens to bacteria and your teeth? Philip: Umm... i t gets in your teeth and they rot away. Religious education classes at school provided more information about bacteria for Sharon: Sharon:  I know in R.E. we did about Lepers. Um, just means the conditions where you catch i t and the way you l i v e .  Apart from this sort of conceptual input from professionals and the media, the pupils also gained beliefs from their own experiences of illness.  Although many believed living organisms were causal factors of  disease, i t was also apparent that many took note of "folklore" that stress the value of keeping warm, not getting wet feet, not going out with wet hair, or getting dirty.  Neil and Mark provided views of this type in  their interviews: Neil:  I went swimming and I didn't dry my hair properly and I got i t (a cold) that way. I've got a bit of a cold a l l the time because I've got asthma.  Anthony: Well i f you were dressed up and you didn't get wet you wouldn't get a cold.  Pupils who have produced quite detailed frameworks of beliefs have done so by recounting stories of their own illnesses and what they have observed on the television.  A few talked of the value of medicines and  vaccinations and how the body copes with disease with knowledge more likely to have been gained from documentaries and books than their doctor. Examples of this are shown in the following interview extracts:  -77-  Robert:  Lee:  Um, i f you have an antibiotic i t usually gives you a very small amount of the germ that you've got, just enough so that your white blood cells can fight back and get used to fighting them.  I think the white blood cells become stronger than the germs and that they eventually take over from them and the next time you get the disease i t doesn't last long because the germs, no not the germs, the blood cells know how to fight i t .  It i s a possibility that pupils have already built complex conceptual frameworks concerning germs or bacteria from many sources.  The pupil has  not come to class with blank minds, he/she has already acquired beliefs concerning bacteria from many possible sources. How tine beliefs making up conceptual frameworks interplay with the experiments investigated i s analyzed in the following sections.  -78-  4.2  Pupils' beliefs elicited from Clinical Interview  Two  The second interview took place after tine pupils had set up the experiment "Bacteria in the A i r " in their practical groups. The interview was conducted before the next lesson when colonies of bacteria were observable on the agar plates.  This section presents the results to the  research questions pertaining to: a)  pupils' identification of bacteria,  b)  pupils' views of bacteria as living units,  c)  the significance of sterile equipment and medium, and  d)  the significance of the control plate.  4.21  Pupils' identification of bacteria A l l pupils who were interviewed identified bacterial colonies on  their agar plates and recognized that there were different types of bacteria on the agar.  This notion was supported by the belief that  different bacteria would have different colours.  Only one pupil used the  idea of shape to distinguish between bacteria but realized that the naked eye could not use this characteristic and the microscope would be needed. A third of the pupils mentioned the colonial nature of the bacterial growths and appreciated the great number of bacteria present in a small colony.  Two pupils commented on the size of the colonies and gave  explanations as to why the colonies varied in size.  Steven appreciated  the relative differences in size between the colonies and justified his statement with an argument that the bacteria had a different rate of division.  This concept was held in the preliminary interviews.  from both interviews are included:  Excerpts  -79-  Clinical Interview One: Steven:  I t (the bacteria) divides every twenty minutes doesn't i t ? I t makes two more so in an hour you've got two, four, eight.  Clinical Interview Two: Steven: I think i t (size of colony) depends on how quickly they divide or i t could be the bacteria in the air and how much there i s of each.  In summary, pupils were as adept at identifying different types of bacteria as one would expect from within the limitations of tine experiment.  Few extended the opportunity for observation by suggesting  looking at the shapes of individual bacteria with a microscope. The concept of the coiony was only at the descriptive level and few could explain why the sizes of the colonies varied.  This lack of explanation  may be due to their concepts of l i f e and the characteristics of living units.  We now turn out attention to the beliefs pupils have about  bacteria as living units.  4.22 Bacteria as living units The pupils' beliefs concerning the l i f e functions of bacteria were revealed in their responses to two questions.  The questions were:  1)  What i s the significance of the sterile equipment and medium? and  2)  What i s the significance of the control plate?  Typical pupil responses of how the experimental procedures can be interpreted i n terms of the l i f e functions of bacteria are provided in the following two sub-sections. Pupil significance of sterile equipment and medium A l l the pupils interviewed argued that i t was important that the agar  - 8 0 -  medium and in some cases the glass petri dishes (plates) should be sterile and that the potential source of contamination was mostly from the a i r . Nicole provides a response that i s typical of the type of arguments used: Nicole: I f i t (the agar) wasn't clean you wouldn't have the bacteria that you wanted because you'd already have something from the a i r when you open them before they came out of the pressure cooker.  Only three of the pupils mentioned the possibility of bacteria being present on the unsterilized glass plates and only two pupils out of the ten interviewed for this experiment suggested that contamination may occur from the agar i t s e l f , although one would have thought the agar appears more likely to be viewed as a food source for bacteria than the glass. For most pupils the main reason for having performed the sterilization procedure, was to obtain a particular type of germ - i.e. bacteria.  the airborne  The other bacteria are the wrong sort as Jane confirms in her  interview: Jane:  There may be bacteria on the dishes before we started and they might be the wrong sort of bacteria that we wanted on the dishes.  There was general agreement as to the importance of sterilization and the source of contamination from the air.  Bacteria are mostly viewed as  disease causing organisms living in some type of host.  It must seem  unusual to pupils that bacteria can be grown on agar in petri dishes. The bacteria are likely to appear on the agar later on in the experiment although how tin i s occurs i s not well understood. The relationship between the bacteria and the glass dish i s such that the bacteria may be on the glass but not be a contaminant since pupils view them as inconsequential. Bacteria are acknowledged to be on the glass but not living.  Philip's  -81-  transcript demonstrates this notion although later he expands upon his position. Int:  Are you saying that the control told us how clean the j e l l y was when we put i t in? Philip: Yes Int: O.K. would i t t e l l you anything else? Would i t t e l l you how clean the glass plates are? Philip: No, you didn't really want to know that we want to know about bacteria in the j e l l y .  Philip's i n i t i a l concepts show him to believe that bacteria cause disease and that they are passed on through the a i r . In his f i r s t interview he stated that bacteria l i v e inside living structures e.g. teeth and the throat.  This appeared to be, for him, a requirement for them to  l i v e and multiply. In this instance he suggests that bacteria could be on the agar j e l l y , but he doesn't view any bacteria on the glassware as being important.  This suggests that he does not believe that the bacteria are  l i v i n g and multiplying in these environments. However, he appreciates the sterilization procedure:  "... i f you didn't (sterilize the plates) the  control would be the same as the others".  Sterilization of the equipment i s viewed as an important procedure, but students do not verify i f the procedure was successful or devise a way to check i f there are any bacteria in the agar at the beginning of the experiment. Question:  The following excerpts from transcripts show this:  How could we t e l l that there aren't any germs in that j e l l y when we started?  Nicole: Because they were cleaned. Int: How do I know that they are absolutely clean? Nicole: Could have looked down at them under a microscope to make sure that there were no germs.  -82-  Steven:  I f you put i t i n the pressure cooker i t i s bound t o get r i d of the bacteria because of the steam and the pressure.  I t appears that although pupils accept the idea of airborne bacteria contaminating the agar r e s u l t i n g i n colonies of bacteria at the end of the experiment, only a few appreciated other sources of contamination such as the glassware or the agar.  Most revert to looking for physical signs of  contamination, which are unavailable, at the s t a r t of the experiment to confirm these sources of contamination.  The time element i . e .  waiting  for the contaminant b a c t e r i a l colonies to grow i n the sealed plate proves to be problematic Question:  as these excerpts  suggest:  How could we t e l l that there aren't any germs i n that j e l l y when we started?  Chris:  Well i t (the agar) would be really c l e a r . Put i t under a microscope, put some under i t . (later):But i f you l e f t i f (plate 4) i t would do what these (plates 1,2,3) have done.  Michelle:  Cause they were s t e r i l i z e d f i r s t and, er, you'd probably see the germs l i k e cause now i t s come out a l l blotchy and that.  Andrew: They were s t e r i l i z e d . Int: How do you know that the s t e r i l i z a t i o n worked? Andrew: Well i t didn't leave any marks.  Andrew seems to believe that bacteria w i l l grow on the glass i n time but does not r e l a t e t h i s idea of growth to what could happen i n the agar. The following t r a n s c r i p t passage reveals t h i s idea: Int: Could we t e l l i f the bacteria were i n the j e l l y before we started? Andrew: I don't know that Int: Could we t e l l there were bacteria on the glass before we started? Andrew: No, I don't think so, i t depends on how long they've been there - i f they're there for quite long they'd be noticeable.  -83-  As seen i n the earlier transcript provided by Philip i t was thought unnecessary to check for bacteria on the glass plates.  He was able to  reason why the bacteria on plates 1 , 2 , and 3 came from the air and why the jelly didn't possess contaminants before innoculation.  He argues:  "Because they've been put in the pressure cooker for fifteen minutes so they must have been clean". ."Because number 4 hasn't got any bacteria in and the other three has" and " i f you didn't (have the agar sterile at the beginning) the control would be the same as the others." Other pupils were unable to include in their frameworks that contamination of the plate may come from the glassware or agar i t s e l f and looked for other sources. These were again related to bacteria being in us and being breathed out as was the explanation in the f i r s t c l i n i c a l interview for pathogens. Nicole:  Er... could come from us because we were breathing every so often.  Therefore, although i t was important that only airborne bacteria were collected, there were few rational ideas as to how to prove that this was indeed the case.  In summary, sterilization was seen as important so as to exclude any but airborne bacteria.  A few pupils believed that bacteria could be on  the glass and agar before sterilization, but i t appeared that even i f they were on the glass after sterilization this was not as important as i f they were on the agar.  It seems that pupils may believe that those on the  glass may not be able to grow. Most students recognized only one source of contamination and that was from the air.  Understanding that sterile  equipment and sterile medium are equally important to the success of the experiment i s necessary to completely understand the significance of the control plate.  -84-  P u p i l s i g n i f i c a n c e o f the c o n t r o l p l a t e To a s c e r t a i n how p u p i l s viewed the c o n t r o l p l a t e (plate 4) they were asked the f o l l o w i n g question: what i s i t ? "  "Is there any purpose f o r p l a t e 4?  I f so  I f p u p i l s appreciated the s i g n i f i c a n c e of the c o n t r o l p l a t e  they would be able t o reason that 1) the unopened s t e r i l i z e d p l a t e with s t e r i l i z e d agar would not produce any b a c t e r i a l growth, even a f t e r f i v e days and that 2) t h i s would prove t h a t no b a t e r i a could have come from the agar or i n s i d e the glass i n the other plates (1,2 and 3) i f these plates were treated equally at s t e r i l i z a t i o n .  3) The only source of  contamination would be the a i r that had been l e t i n t o plates 1,2 and 3 after s t e r i l i z a t i o n .  Samples o f answers t o the above question f o l l o w : Steven:  ...so that we could see i f b a c t e r i a seeped i n through the g l a s s , through the gaps or even through the glass onto the agar.  Andrew:  To see i f the germs could get i n there. Through these l i t t l e gaps at at the bottom and could see i f they could go i n a place that hadn't been touched with anything they can breed there.  Jane: To see i f the, um, germ or b a c t e r i a could get i n t o p l a t e 4 while i t was closed i n any way. Jonathon:  Philip: Chris:  ...see i f there were any bacteria i n the p l a t e before we s t a r t e d . . . . i f the p l a t e stays closed (we) would see i f anything grows at a l l with i t closed... see i f any could get i n , yes. I f i t ' s closed they can't r e a l l y get i n .  You've got t o get a l l of i t clean. I t ' s so you can compare the d i f f e r e n c e s , so you can see how much more one's got t o the one that wasn't open.  -85-  Michelle:  We wanted t o see what the one outside would be l i k e and then put i t against t h i s one and see what d i f f e r e n c e there would be. I t t e l l s us that the agar was s o l i d and i t ' s j e l l y . I f i t wasn't clean i t would be a d i f f e r e n t colour t o t h a t and i t ' s j u s t a l l one colour and you couldn't see any germs i n i t . You could j u s t see what i t would be i n comparison w i t h um the other two dishes but there's not r e a l l y a point f o r having p l a t e 4.  There were three major ideas produced by the answers t o the question concerning the c o n t r o l p l a t e : 1) That i t was t o see i f b a c t e r i a could get i n t o a closed p e t r i d i s h , 2) So t h a t we can compare t h i s p l a t e to the other three t o see the amount of growths on the p l a t e s , and 3)  To see i f there were any b a c t e r i a i n the p l a t e s before the experiment started.  The f i r s t two major ideas were popular w i t h p u p i l s . P u p i l s e s p e c i a l l y l i k e d the idea of comparing the absence of b a c t e r i a i n p l a t e 4 with b a c t e r i a present i n p l a t e s 1,2 and 3.  At l e a s t w i t h t h i s idea confirmed  to themselves that the experiment had worked!  The p u p i l s who held the  t h i r d i d e a (two, i f P h i l i p ' s previous statements are included) d i d not say how p l a t e 4 could show that no b a c t e r i a were i n the p e t r i dishes a f t e r s t e r i l i z a t i o n and before the i n n o c u l a t i o n of a i r b a c t e r i a . They a l s o were unable t o s t a t e that t h i s p l a t e would i n d i c a t e a high p r o b a b i l i t y that the b a c t e r i a from p l a t e s 1,2 and 3 were from the a i r .  4.23  P u p i l s ' o v e r a l l understanding of the experimental  procedures  Apart from s t e r i l i z a t i o n and c o n t r o l procedures, there were other i n s t r u c t i o n s that had t o be taken i n t o account i n order t o understand  -86-  the experiment and i t s results.  A l l the pupils interviewed appreciated the need for washed, clean hands while handling the plates i n order to prevent contamination i n the agar.  Pupils believed that the petri dishes were placed outside, or in  a draughty place or in a draughtless place to assess the different amounts of bacteria in the air currents.  It was also generally accepted that the  plates i n the draughty exposures would catch more bacteria since there would be more bacteria "flying" over the plate and likely to drop in. Nicola makes a statement with this view: "To see what the difference would be i f you put one in a non draughty thing there probably wouldn't be as many germs flying around the air when i n the draughty one there'd be more germs flying around." To achieve a draughtless place a cardboard barrier approximately  three  centimetres high was used to encircle the plate. This provided conflicting results and different explanations by pupils.  Here i s an  example from one transcript: Chris:  Well in the draughty room the germs are blown over i t and go into i t more easily and when, cause they wouldn't be able to get into the cone around i t so easily.  For Jane the plate l e f t outside had more bacteria because there were more "germs" outside than i n . The draughtless plate with the shield stopped germs getting in. Steven i s less sure in his explanation: "I think that in the non draughty you would get more of the, because of the um well i t isn't draughty so the bacteria just goes down but in a draughty place the bacteria goes over i t but i f you put i t outside bacteria also goes over i t and i t slows down and goes on i t . In a draughty place i t ' s always draughty a l l the time.  -87-  I t was v a r y i n g and  not a p p r e c i a t e d  be  constantly  t h a t by k e e p i n g the p l a t e s open f o r twenty minutes an  o f the c o n d i t i o n s was open f o r l o n g e r s e t t l e on the  The  t h a t " l o c a l " wind speeds may  achieved.  than a few  A l l p u p i l s claimed  minutes i n o r d e r  t h a t the p l a t e s were  t o a l l o w enough b a c t e r i a t o  agar.  main problem w i t h t h i s experiment was  b a c t e r i a l source was  s o l e l y from the a i r .  t r y i n g t o show t h a t  P u p i l s saw  In order  t o understand the c o n t r o l and  the  the need f o r t h i s  but f a i l e d t o match up b e l i e f s w i t h v i s u a l e v i d e n c e p r o v i d e d control.  average  by  the  i t s usefulness  for  e l i m i n a t i n g sources o f c o n t a m i n a t i o n the p u p i l s needed t o a p p r e c i a t e  that  a l l b a c t e r i a i n s i d e the p l a t e were p o t e n t i a l contaminants s i n c e they a l l were l i v i n g and appreciated  showing c h a r a c t e r i s t i c s o f l i v i n g t h i n g s .  not  by most s t u d e n t s s i n c e p u p i l s appeared t o have vague b e l i e f s  about the l i f e concepts o f b a c t e r i a . revealed  T h i s was  b e l i e f s concerning  In t h i s experiment p u p i l s have  the l i f e o f b a c t e r i a which suggests t h a t  the  b a c t e r i a can be found i n the a i r , sometimes on the g l a s s p e t r i d i s h ,  and  sometimes i n the agar medium.  However, b a c t e r i a a r e not always viewed as  l i v i n g i n these environments s i n c e p u p i l s do not always r e c o g n i z e they are c o n t i n u a l l y undergoing d i v i s i o n f o r r e p r o d u c t i o n .  If this  concept i s h e l d the b a c t e r i a on the g l a s s are not mentioned as important.  A more l i k e l y  explanation  i n t o the c l o s e d  r a t h e r than the s t e r i l i z a t i o n process h a v i n g f a i l e d and i n the p l a t e as a l i v i n g ,  being  f o r p o s s i b l e contamination of  c o n t r o l p l a t e would have i n v o l v e d b a c t e r i a seeping  being  that  reproducing  unit.  The  bacteria lack of  the dishes  still  life  c o n c e p t s appear t o p l a y an important p a r t i n p u p i l s ' u n d e r s t a n d i n g o f experiment.  T h i s w i l l be d i s c u s s e d  i n more d e t a i l  i n Chapter  5.  the  -88-  The third phase of the study involved a second experiment "Bacteria on Ourselves" which uses the same practical techniques and w i l l be discussed in the next section.  4.3  Pupils' beliefs elicited from Clinical Interview Three This third phase of the study involved interviewing ten more pupils  from the same second year class. After performing the f i r s t experiment i t was believed that the pupils would use this prior learning experience and gain a greater depth of understanding of the second experiment. This third interview was given after the experiment "Bacteria on Ourselves" but before the results were available.  This enabled pupils to predict the  results they thought they would obtain. The information gained from this part of the interview i s reviewed in the f i r s t subsection presented. Other subsections deal with pupils' views of the significance of sterile equipment and medium, pupils' significance beliefs about the importance of the control plate, and finally, the overall understanding of experimental procedures.  -89-  4.31  Predicted results A l l pupils were asked to predict the results of the experiment. This  provided a fairly uniform answer that can be summarized as follows: Plate A  Unwashed Hands: This plate was expected to have the most bacteria on i t .  Plate B Washed Hands: The plate that was innoculated with bacteria from washed hands would provide a smaller source of bacteria since washing was expected to remove bacteria from the skin. Plate C Unopened: A l l pupils expected this to be free from bacterial colonies since the plate had remained unopened and later they were sealed with cellotape and put in the incubator. Justine used her home experiences to justify this prediction: "Because i t hasn't been opened and when you i f you have food at home and you just close i t up i t doesn't go mouldy or anything." Although the plate was closed, Mark revealed a common idea that was also apparent i n the previous experiment: "... but some could seep because i f they were floating in the air and i t wasn't cellotaped up and i t wasn't sealed in so I don't (know). Some bacteria might have been able to come in from the air but i t would spoil the experiment." In fact, six of the nine pupils believed that the bacteria may enter the plates from contaminated air because bacteria may enter the plates i f they were opened too long.  Lewis provides an example of this belief:  "... because when we opened i t the air got to i t as well." A third of the students believed that although there may be airborne bacteria in the cultures they could be distinguished from those on the hands.  An example of such a statement i s provided by Nicola:  -90-  "Well in the previous ones which we had done were a l l different colours but ones that just come from our hands are white ones so we could t e l l the difference between them cause the other ones were like they were fungi and that you know and wouldn't be able to get those on your hands and so you would have that on the agar which was from the hands' experiments." Robert also suggests: "We could compare them with these (point to drawings of bacteria from previous experiment)."  Another distinguishing factor i s  provided by Mark: "There's two different kinds of bacteria probably the one in the air you know, you know is detailed. Got lots of, you know, dirty marks and that, but on your hands i t probably hasn't got very much, you (know), because you wash them ...."  The predicted results show that a l l the pupils have an understanding of the experiment as far as an expectation of results. However, there i s s t i l l some doubt about the role of plate C - the control plate in this experiment.  Although the pupils believed that i t would remain clear, two  pupils s t i l l believed that some bacteria might be able to seep into the agar plates.  Pupils appear to have learnt from the previous experiment  that airborne bacteria could contaminate the plates when the petri dishes were opened and that identification of these bacteria might be useful in order to discriminate between the bacteria from the air and bacteria from the pupils' hands. Contamination of plates and i t s consequences as pupils see them i s discussed in the next section.  4.32 Pupils' views on the significance of the sterile equipment and medium A l l the pupils appreciated the need to sterilize the equipment and most pupils provided an argument as to how they knew that the sterilization had worked.  Pupils had to control contamination from not  -91-  only the air, as they found out in the f i r s t experiment, but also from the equipment.  Several pupils provided examples of their beliefs as to  why sterilization was done. Richard:  Sharon:  So there aren't any germs in there so you can t e l l or know that you only got the germs from your hands. They'd been sterilized so no dirt could be on them... you'd be able to see the colours of them.  Mark: I f they weren't clean the bacteria from the air and your hands would get in there before the actual experiment because we are trying to find out that bacteria are on our hands and not in the a i r . Most pupils view the need to controlling contamination as important and in this interview seven pupils provided suggestions as to how the success of the sterilization procedure may be proved. Evidence for successful sterilization are provided in the following excerpts: Lewis:  Heat them up very hot and leave them to cool down. If you put i t in an incubator and take i t out after a while there shouldn't be any bacteria on i t .  Lewis does not reason why bacteria are absent on the plates but Robert does: "I suppose you could test i t i f you put some agar in and you had a l o t of them and you just took one and put some agar in i t then i f any bacteria grows then you know that the dish isn't sterile but i f there i s nothing there then you know i t i s . " However, there are problems s t i l l occuring with the time lapse incurred by having to wait for the bacteria to grow. There are s t i l l views that one could t e l l i f the agar and glass plates were sterile by examining the plates immediately after the sterilization process as can be seen by the following excerpt:  -92-  Nichola: I suppose there'd be a different bacteria for that j e l l y because um i t ' s meant to be sterile before we started so i t would probably just have l i t t l e black bits in i t i f i t wasn't really clean.  If the sterilization process i s fully appreciated pupils should be able to cite plate C as proof that sterilization has been successful and that this in turn t e l l s us that the bacteria growing on the agar are, most probably, from our hands.  The views of pupils concerning the  significance of the control plate i s discussed in Section 4.33.  4.33 Pupils' views on the significance of the control plate in the experiment The two pupils who showed the most logical argument on the significance of the sterilization process connected their argument to' the purpose for plate C - the control plate.  This is Robert's argument for  plate C: "... oh, um to test whether the dishes are sterile and um don't know about i t .  ... to make sure the bacteria in these plates isn't the  bacteria from the actual dish or the agar."  Robert indicated in an  earlier interview an understanding that bacteria are able to multiply and make more germs. Deborah also revealed the belief that bacteria could reproduce themselves and claimed that plate C would prove the other plates sterile " i f there wasn't any bacteria on C at the end of the experiment." Deborah did not extend this argument to eliminate unwanted contaminant bacteria and prove the bacteria growing had come from the hands only. The other pupils confidently expected Plate C to be free from bacteria but this was only because the plate hadn't been opened.  Sharon suggested  checking the agar with a microscope therefore indicating that she may not expect to see the bacteria easily. When asked about the purpose of plate  -93-  C, Sharon  v o l u n t e e r e d , "... t o show what t h e p l a t e would l o o k l i k e  any germs i n . " Sharon  produced  without  one o f t h e more complex concept maps  i n c l u d i n g t h e l i f e concepts from the f i r s t b e l i e v e d t h a t b a c t e r i a reproduced  clinical  interview.  " l i k e f a m i l i e s do".  a p p a r e n t l y d i d not use t h i s concept o f r e p r o d u c t i o n  She  However, she  when d i s c u s s i n g t h e  purpose o f p l a t e C.  J u s t i n e a l s o c l a i m e d t h a t p l a t e C reminded looked l i k e i n the f i r s t common i d e a  place  so we c o u l d  us what the experiment  see how much i t changed - a  p r e s e n t e d by p u p i l s i n b o t h e x p e r i m e n t s . She saw t h e need f o r  s t e r i l i z i n g t h e p l a t e s a t the b e g i n n i n g o f the experiment stated,  s i n c e she  " b a c t e r i a from o t h e r experiments might be on i t . "  Although p u p i l s viewed  t h e need f o r c o n t r o l l i n g c o n t a m i n a t i o n as  important, t h e l i m i t e d number o f p u p i l s b e i n g a b l e sterilization  had t a k e n p l a c e  resulted in s t i l l  t o prove  that  fewer p u p i l s h a v i n g a  full  u n d e r s t a n d i n g o f t h e r o l e o f the c o n t r o l p l a t e i . e . t h a t 1) p l a t e C demonstrated eliminated  that s t e r i l i z a t i o n  had been s u c c e s s f u l , and 2) t h a t i t  c o n t a m i n a t i o n from the agar and g l a s s so l e a v i n g c o n t a m i n a t i o n  only occuring  from the hands.  I t i s possible that l i m i t e d l i f e  may a f f e c t t h e way p u p i l s view proving s t e r i l i z a t i o n  4.34  e s p e c i a l l y with reference  has occured and t h e r o l e o f t h e c o n t r o l p l a t e .  P u p i l s ' o v e r a l l u n d e r s t a n d i n g o f t h e e x p e r i m e n t a l procedures  The p u p i l s appeared for  the experiment  concepts  the experiment  to find  even though  i t easy t o make the c o r r e c t  predictions  they e x p e r i e n c e d some d i f f i c u l t y i n  e x p l a i n i n g t h e i r r e a s o n i n g behind t h e s e p r e d i c t i o n s .  Throughout t h e  to  -94-  interviews i t was also apparent that pupils were more satisfied with obtaining an answer that they saw as correct rather than having a logical explanation.  Examples of this attitude are revealed in Section 4.4.  Pupils were accomplished answer seekers without being reasoners.  Pupils found the second experiment easy to perform.  This was  probably because i t only involved three plates and uncomplicated procedures.  Pupils did not attach a l o t of importance to the agar in i t s  role as a food source or as a potential source of contamination.  Three  pupils mentioned that the agar provided food for the bacteria while two pupils said that the bacteria did not feed on the agar.  This i s an  indication that l i f e concepts are not very strong and may influence the pupils' judgement as to what i s going on in the petri dishes.  The air was seen as the chief source of contamination and the idea that bacteria may get up through the glass occured on two occasions. However, most pupils appeared to have reasoned that contamination through the gap in the petri dish happen and confirmed this by predicting plate C to be free from bacteria. Beyond the physical appearance of plate C, most pupils were unable to state i t s role in the experiment. Sterilization had an important part to play in the task but most pupils were unable to relate this belief to any sort of meaning for the control plate.  With these conclusions in mind, i t i s pertinent to look at the pupils' perceptions of the two experimental tasks when parts of the experiment have limited relevance to the task , e.g. in experiment one plate 4 and in the second experiment plate C.  -95-  4.4  P u p i l s ' perceptions o f the two experimental tasks The dialogue of two groups of p u p i l s were recorded while they  set up each experiment.  The p u p i l s were then asked t o provide w r i t t e n  answers t o questions concerning the method of the experiment (provided i n Appendix E ) . T r a n s c r i p t s of recordings were then produced and analyzed for p u p i l s ' views on a) i n s t r u c t i o n s being followed, b) a c t i o n s being c a r r i e d out, and c) r e s u l t s . These are three aspects of laboratory work s i m i l a r t o those discussed by Tasker (1980).  4.41  Experiment one: " B a c t e r i a i n the A i r " The f i r s t experiment " B a c t e r i a i n the A i r " produced two t r a n s c r i p t s  from a boys' group and a g i r l s ' group. These were l a b e l l e d Group 1A and Group 1B r e s p e c t i v e l y . Group 1A The boys were q u i t e comfortable being recorded and commenced recording when they were a l l seated and ready t o s t a r t .  The i n s t r u c t i o n s on the printed work sheet were followed i n a recipe-type fashion with i n d i v i d u a l p u p i l s reading out the i n s t r u c t i o n s . I t appeared t h a t p u p i l s had glanced over the i n s t r u c t i o n s before s t a r t i n g , but t h i s provided confusion since they d i d not obtain enough information about the general plan o f the experiment. Features such as how long the agar p l a t e s were open were not questioned, but s t r i c t timing of how long  -96-  the plates were open was observed.  This i s demonstrated in the following  excerpt: Robert: Mark: Steven: Robert: Mark: Robert: Mark: Robert: Steven: Mark: Robert: Steven: Robert:  (reads) Choose a draughty place in the laboratory, take off the l i d and expose the .... Open the window - draughty place. Yes, there i s . It says put the f i r s t one Plate One (reads) Expose i t to the air. Yes, plate one. (reads) For twenty minutes. Right on your marks get set. I ' l l time i t . Look, there's a clock up there. Alright, what do we do now? Haven't you got something to put 'round i t ? You put both plates out don't you? No, only one.  Why they are following the instructions and how these f u l f i l l the purpose of the experiment i s only revealed when one member of the group asks what they are doing and why. Only one person discloses that he understands the whole structure of the experiment at this point. (The group i s labelling up the plates) Mark: Martin: Mark: Martin: Mark: Martin: Robert: Mark: Robert: Mark: Steven: Mark: Martin: Steven: Mark: Robert: Mark:  There, do i t on number two, do i t on the l i d of number two. What was in that one? Er. What was in that one? Was that the lid? The j e l l y , i t ' s the j e l l y . What are we doing? What we are doing i s testing for bacteria and we've got some jelly here. And on.the windowsill in the draught. We're testing the bacteria in the air. And here we're going to exclude (the) draught from the jelly and see... For twenty minutes. No, i t doesn't. It i s . How are you going to test what bacteria's in that one? It's going to take two days. Well this w i l l test i f there's bacteria in the air, won't i t ? Yes. And this w i l l test to see i f there's bacteria just floating about and not in the draught. What i s number three then?  Mark states that the plates have to be l e f t open for twenty minutes with the draught excluder, but he i s unsure that i t w i l l take at least two  -97-  day s, according to Steven, to obtain a result to the experiment.  This  confusion i s revealed once again when the boys answered the questions about the methods used.  The boys go on to answer the questions about the experiment and they reveal a common misconception concerning bacteria seeping into the petri dish.  They also show a commitment to their task in the following  excerpt: Martin: Bacteria could seep into the closed container. Steven: Yes. Robert: If you could break into the seal. Mark: (Steven) Lang's just messing around. Robert: I know and blabbing into this recorder i s important....  Although the group was asked why the petri dishes had to be sterile at the beginning of the experiment, Robert inadvertently changes the emphasis of the question by only considering why the agar solution has to be clean without a challenge (from the other members of the group). A l l the boys agreed that bacteria would be everywhere and on our hands so equipment and hands had to be clean. Robert also influenced the group's decision that plate 4 was l e f t open to see i f anything could get in although Mark did suggest that i t was l e f t to see i f i t changed after being l e f t for a while.  Pupils were asked to predict their results.  Although Steven has already stated that the results would take two days to assess from the plate, the other members of the group ignored this part of the experiment and produced results.  Part of the problem i s that Steven  suggests that the dirt and dust on the plates i s bacteria, but he i s not totally sure about this. The others are not convinced either and probably think that i f i t i s only dust they would not be able to write down any  -98-  results immediately so they take i t to be bacteria. This may suggest that the boys perceive the recording of a result for the experiment as extremely important. Robert: Mark: Robert: Steven: Robert:  Let's have a look at (plate) number 3. This i s the worst one exposed to the most a i r . The one exposed to the most a i r Is that bacteria? The one exposed to the most air  Steven: Martin: Robert:  Hey look, i s that bacteria? Or the draughtiest place. Of course i t ' s bacteria.  Later on in the transcript: Steven: Mark: Robert:  It says you have to wait two days in an incubator. Just say what the results are now. Here are our results now after exposing our plates to certain whizzes and a i r . Steven: On plate one we have a swirl effect with minute pieces of dust. Robert: What was plate one, where was i t ? Steven: And plate one was outside our room near a draughty door. Mark: Martin: Robert:  Plate 3 seems to have a l o t of bacteria on i t because i t was outside on a ledge and has grains of dirt from the wind blowing bacteria onto i t . Right, i s that i t ? Yes.  Group 1 B This group consisted of three g i r l s .  They read part way through the  instructions and then proceeded, in not quite as recipe-following a fashion as the boys and apparently with more independence from the instructions. Nicole: We have to put this around i t , don't we? Sally: Er, yes, do that a minute. Nicole: Do we (do) that - i t says, oh that's three isn't to do a draughty thing. Nadine: No, you can choose any number you want.  -99-  When i t came to timing how long the plates were open, they were careful to be accurate.  However, they could not decide how open to leave  the plates and so a discussion arose: Sally: Nadine: Nicole: Sally: Nadine: Sally: Nicole: Sally: Nicole: Sally: Nadine: Nicole: Nadine:  Here, just leave i t here or on the windowsill. Just put i t near the window here. Inside. Yes. Ajar. Ajar. Just a l i t t l e bit ajar. Half way. Half way. The outside one should have been ajar, No, i t shouldn't, Half way. Um, i f you want, alright.  Eventually i t was decided that i f one plate was to be opened half way then a l l the others should be placed open half way.  This concept of fairness  of equal conditions for each plate i s not the same as the concept of fairness portrayed in the following paragraph.  The notion of fairness in this section refers to avoiding cheating to obtain the correct results. The results are seen as important, after a l l the experiment would be a success i f bacteria grew. Although growth of bacteria i s the required aim of the experiment, the bacteria must only come from the air. Nadine: We started the experiment with clean hands. Nicola: So that we never had any bacteria on our hands. Do you agree with that? Sally: Yes, so we started the experiment - well, i f you hadn't i t wouldn't have been f a i r , would i t ? Nicola: It wouldn't really have worked. Sally: It would have been cheating in a way. Nadine: We started the experiment with clean hands. Nicola: ... to prevent getting bacteria on the plates. However, the questions that were answered by the group were seen as something to be assessed and not as a tool that w i l l aid their  -100-  understanding by encouraging pupils to listen to other viewpoints. Nadine: Question 4, 'the plates were l e f t open for a long time. Why was this?' Nicola: Because they could get enough, to make sure they get enough bacteria. Sally: That's quite a good answer, I think that'll do. The answers to the questions were viewed as likely to be assessed and so some sort of answer was required. Nadine: Is there a purpose for plate 4? Sally: I think so. Nadine: Yes. Sally: What do you think, I think there probably i s a reason for i t , a purpose. Nicola: Yes. Sally: We reckon there i s a purpose for i t . Nadine: We can't put reckon. Nicola: Yes, we think there i s . Sally: It says what i s i t i f there i s one. Nadine: Um, er, just leave i t . (Discussion goes on) Sally: Have we got to do question 5? Nadine: Oh, shut up. Nicola: Listen, to leave on that hasn't got bacteria on i t and to leave open one that i s you could see the difference maybe. Nadine: That's probably the idea, yes yes, just write that down anyway. Nicola: Go on then.  This gives the impression that the idea w i l l do although i t i s not certain that the statement answers the question correctly.  Any internal  conflict within Nadine i s quelled by having an answer for the question.  The two groups of pupils worked through the experiments with different styles.  Both were negligent in reading through a l l the  instructions to the experiment prior to commencing the setting up of the experiment.  However, the girls appeared to reflect more on the  construction of the experiment and perceived no problem in reordering the order of completing each activity with the plates. The boys were far more  -101-  cbncerned with following the experiment in a recipe-like fashion. The boys' reflection on their activity only occured when one member of the group asked what was happening and how the bacteria were going to be tested. This resulted in the pupil organizing his own thoughts about the experiment.  In the other group, the girls decided that being f a i r in  opening the plates a l l the same distance was important therefore showing that they considered the process in the experiment. Pupils only began questioning procedures in the experiment when they became involved in answering the questions provided by the researcher. In the boys' group there was an incident that suggests that pupils view the questions as a task not an opportunity to clarify their ideas concerning the experiment.  The task i s to answer the questions as quickly as  possible even i f i t requires a restructuring of the question.  4.42  Experiment two:  "Bacteria on Ourselves"  Again there were two groups, one female, one male who recorded their progress through the experiment.  Unfortunately, the girls edited their  tape during the experiment by switching i t off between procedures, therefore cutting out the excerpts of discussion that show the progress in argument resulting in understanding the experiment. This i s an interesting move that the g i r l s made. Obviously they did not appreciate that their discussion was of any value to the teacher.  Perhaps this i s a  reflection of how they view their work and how they see a l l school work being assessed in i t s final form and not during i t s synthesis. Further discussion on these attitudes and others reflected from these group work transcripts i s provided in Chapter 5.  -102Group 2B This group, comprised of three boys, quickly engaged themselves with the experimental tasks without any problems. Previous experience should have helped and they also only had to use and open two plates while the third was left alone and unopened.  From the transcript it was not apparent whether they read a l l the experimental procedures prior to innoculating the plates. These pupils did not show any signs that they were mechanically following the procedures listed on the work sheet since i t appears they quickly decided on the practical procedures of the experiment.  After setting up the plates this group embarked on answering the questions.  The questions were not seen as important. Between diversions  to look at the laboratory animals i t took l i t t l e effort to agree on the answers to the quesions. Only when they came to discuss plate C was there uncertainty and Chris attempted to air his views. Andy: Michael: Andy: Chris: Andy: Chris: Michael: Chris: Andy: Chris: Andy: Chris: Andy: Michael: Chris:  Do you think bacteria will grow on plate C? No. No, because.... No, because i t hasn't been opened. Because i t hasn't been, well it might have been. Yes, because the bacteria.... Plate C. I know, because the bacteria could be out (side), could get through to the plate. No, I don't think so. No, that's good. Just put no. Well I think i t should. Well you're wrong. Two against one. What's number five? No, what's number six?  Although Andy does not give reasonable objections against Chris's  -103-  argument, he succeeds in gaining Michael's approval and Chris gives up his challenge.  The transcript shows that group pressure wins this discussion  and this results in Chris not participating in the rest of the discussion. Andy: Chris: Andy: Michael: Chris:  Why do you think we had plate C? Er, to.... Because we could. To see i f bacteria could grow in plates taped up? Yes. Come on question number seven, we are on the last one.  It appears that the dynamics of the group have prevented Chris from developing the conversation any further. This may be a tactic of the other members of the group i f they consider answering the teacher's questions as the task and do not view other pupils' views as helpful in clarifying their own views of the experiment.  Although the practical work does not appear to have been very stimulating, this i s perhaps a reflection of the dynamics of the group. Individual interviews provide much more insight into an individual pupil's thinking about specific concepts and laboratory procedures, but these transcripts have the merit of disclosing some very relevant problems of teaching laboratory work and the use of group work in laboratory situations.  4.5  These issues w i l l be discussed in more detail in Chapter 5 .  Results of group work (written answers) For both of the experiments, the pupils worked in groups of two's or  three's and after each experiment they were asked to reflect on aspects of the experiment and record their ideas.on an overhead acetate sheet with the intention of later presenting their answers to the class.  From the  analysis of these data sources i t i s possible to look at the substantive  -104-  beliefs of a large proportion of the class concerning the sources of contamination, sterilization procedure, and the role of the control plate in both experiments.  For the f i r s t experiment there were eleven examples  of group work and from the second experiment there were nine pieces of group work presented. "Bacteria in the Air" Pupils claimed that the sterilization procedure, implemented before the practical work commenced, resulted in a l l the plates being free from bacteria.  A popular belief about sterilization was that once i t was done  i t was successful.  Five groups reasoned that sterilization was necessary  to prevent bacteria being present in the dishes before the experiment began.  None of the pupils explicitly claimed that the potential  contaminating bacteria from the agar or the glass plates could be mixed with airborne bacteria in the f i r s t experiment, but there were justifications suggesting that bacteria would be present i f sterilization didn't take place and that these would nullify the experiment.  A l l the pupils appreciated that our hands could introduce contamination into the plate, either in the form of "dirt", "germs", or bacteria. jelly.  Two groups mentioned that the "germs" could spread onto the  This suggests that the pupils either view the bacteria as having  the potential to move or to grow and cover the agar.  Predicted results for experiment one showed that pupils expected the j e l l y to show "blobs" of bacteria or germs that mark the agar.  Three  groups believed that the amount of bacteria covering each plate would depend either on the amount of air that the plates had been exposed to or  -105-  the situation in which the plates were placed.  One group suggested that  the plate that had been covered the whole time (the control plate) would have no germs.  When asked the purpose of plate 4 (control plate, experiment one) another group suggested that this plate would be germ free but would also act as a comparison for the other plates.  Three groups believed this,  while two groups suggested that perhaps i t could test i f bacteria could seep into the plate.  Another group suggested that plate 4 had a purpose  to show that no bacteria could contaminate the agar.  Although they did  not clearly verbalize the role of the control plate, their previous thoughts concerning the purpose of the sterilization process suggests that they have a clearer concept of plate 4 than most other groups.  They  stated that after sterilization "no germs could create on the dishes and they (the dishes) would be sterile."  Their statement "... their i s a  purpose to plate 4. No bacteria can get to i t " may be a reflection on the previous statements cited by this group, but none of the groups went on to say what plate 4 would be able to prove.  In the second experiment seven groups thought that bacteria would not grow on the control plate; four of these suggested that this was because the plate hadn't been opened. successful.  A l l have assumed that sterilization was  Two other groups probably held this assumption, but these  pupils believed that there may be a chance of the bacteria entering through the "gap in the jar" or just by getting through to i t .  Another  group did not think this "seepage" was possible because the bacteria could not get into the dish.  This group later went on to say that plate C (the  -106-  control plate) was in the experiment "because we can see i f bacteria can grow on an unopened plate."  They did not reveal where they thought the  contaminating bacteria would have come from so they could not be said to have grasped the total meaning of the control.  Although, in the second experiment, the pupils put forward the view that no bacteria would grow on the control plate, this plate s t i l l held l i t t l e importance for them. The control did take on some meaning in each group but mostly in a comparative role. Four groups believed i n this role ignoring the obvious that i t was easy to compare something in plates A and B against "nothing" i n plate C. The use of this idea increased in this experiment while the notion of the control being useless decreased to n i l . This could be a reflection of the influence the f i r s t experiment had on the pupils' perceived functions of procedures in the experiment.  Also on  the increase was the belief that the control plate was to check i f bacteria were seeping into the experiment.  Three groups believed in this  despite, in the previous experiment, having evidence that this was unlikely to occur since past control plates had negative bacterial growth. Two groups wanted to see that no bacteria had grown in the control plate, but they did not explain what this would prove and they did not suggest where the bacteria may have come from.  This written work shows that in general the pupils have not appreciated the f u l l extent of the sterilization procedure and how this i s linked with the role of plate C. Although they hold a general idea that bacteria are everywhere, pupils do not explicitly state where contaminating bacteria could have come from and how this could be proved.  -107-  However, i t must be said that pupils attempted to reason the purpose of the sterilization procedure instead of dismissing i t as a task that i s just done and the control plate gradually took on a purpose - for some this was s t i l l the comparison of plates, for others to see i f bacteria could seep in, and for a small number to see that bacteria w i l l not grow. This latter concept goes part way towards a more scientific explanation of the purpose of the control plate, but development of this concept may depend on other beliefs such as nature of l i f e processes that bacteria possess.  The influence of these other beliefs and their possible  interplay with pupils' perceptions of the experiment w i l l be discussed in the next chapter.  -108-  CHAPTER FIVE 5.0  Introduction This chapter discusses p u p i l s ' b e l i e f s about b a c t e r i a and examines  the way i n which p u p i l s ' b e l i e f s concerning b a c t e r i a i n t e r a c t with t h e i r understanding of experimental procedures involved i n the two experiments used i n t h i s i n v e s t i g a t i o n .  The chapter reviews p u p i l s ' use of p r i o r  b e l i e f s when i d e n t i f y i n g b a c t e r i a on the agar p l a t e s , looking at colonies and t h e i r varying s i z e s , explaining the purpose of s t e r i l i z i n g the medium and p e t r i dishes, and the r o l e of the c o n t r o l p l a t e .  From the a n a l y s i s of the data i t was found that some concepts are useful i n helping p u p i l s explain s i g n i f i c a n t aspects of the experiments. The concepts of growth and reproduction were useful i n explaining the importance of the s t e r i l i z a t i o n process and the r o l e of the c o n t r o l p l a t e . Other p u p i l s who d i d not possess the correct s c i e n t i f i c framework o f these concepts were l e s s successful i n i n t e r p r e t i n g the data obtained from the two experiments. S e c t i o n 5.3 i s a d i s c u s s i o n of the use that some p u p i l s make of t h e i r concepts when explaining the purpose of the s t e r i l i z a t i o n process and the r o l e of the c o n t r o l p l a t e .  The a n a l y s i s of group work t r a n s c r i p t s and the w r i t t e n work produced by these groups revealed p u p i l a t t i t u d e s towards laboratory work.  The  importance of these a t t i t u d e s and p u p i l s ' p r i o r b e l i e f s i s discussed, reference t o teaching s t r a t e g i e s , i n section 5.71. Suggestions f o r f u r t h e r research are presented i n the f i n a l section of the chapter.  with  -109-  5.1  Discussion  o f p u p i l s ' b e l i e f s about b a c t e r i a  The i n i t i a l interview of thirty-one p u p i l s produced p u p i l s ' substantive  b e l i e f s concerning b a c t e r i a .  I t was not s u r p r i s i n g t o  discover that p u p i l s have b e l i e f s about b a c t e r i a p r i o r t o formal i n s t r u c t i o n since the l i f e experiences of a c h i l d i n today's world would provide many l e a r n i n g o p p o r t u n i t i e s ,  e.g. v i s i t s t o the d e n t i s t or doctor,  and watching t e l e v i s i o n .  The concept of a bacterium i s not i s o l a t e d from other concepts. The m u l t i p l i c i t y o f the p u p i l ' s concept of b a c t e r i a can be seen as a set of r e l a t i o n s h i p s between concepts w i t h i n a conceptual framework.  To c l a r i f y  the r e l a t i o n s h i p between concepts and t o g r a p h i c a l l y demonstrate the r e s u l t i n g framework, concept maps can be used (see Appendix A2).  I n each  map there are many d i f f e r e n t concepts making up the composite b e l i e f of bacteria.  Some concepts e.g. the concept "small" are w e l l defined and  present i n many of the p u p i l s ' frameworks.  Others such as the concept  "bacteria are l i v i n g " are present but do not possess subsuming concepts that give meaning t o the concept.  This may be because the concept of  " l i v i n g " i s not w e l l understood, p a r t i c u l a r l y with respect t o micro-organisms.  Many p u p i l s believed that b a c t e r i a were l i v i n g , but p u p i l s ' b e l i e f s about b a c t e r i a varied throughout the c l a s s because each p u p i l held a v a r i e t y o f r e l a t e d subsuming concepts that made up his/her b e l i e f s about bacteria.  The meanings attached t o the r e l a t i o n s h i p s between these  subsuming concepts gave v a r i e t y t o the p u p i l s ' conceptual frameworks. For many p u p i l s the concept " l i v i n g " assumed a d i f f e r e n t meaning with respect  -110-  to t h e i r b e l i e f s about b a c t e r i a , but the heterogeniety of the b e l i e f i s a r e s u l t of the r e l a t i o n s h i p between concepts i n the conceptual framework.  Concepts make up the framework of p u p i l s ' b e l i e f s about b a c t e r i a . These concepts, as has already been s t a t e d , are not i s o l a t e d from each other.  Teachers could be more e f f e c t i v e i f they recognize these concepts  and researchers discover how they are r e l a t e d t o each other.  In the  r e s u l t s s e c t i o n (4.1) i t was recorded that many p u p i l s viewed b a c t e r i a as s m a l l microscopic " t h i n g s " t h a t cause disease. These diseases are thought to spread from animals or, more commonly, from people breathing, coughing and sneezing. I t was thought t h a t d i f f e r e n t diseases were caused by d i f f e r e n t types of b a c t e r i a and some p u p i l s reasoned that i n order f o r diseases to occur, b a c t e r i a must be a l i v e .  A few p u p i l s declared that  b a c t e r i a had t o be a l i v e to get i n t o our bodies and t o know where t o go. Many p u p i l s possessed a l t e r n a t i v e concepts of " l i v i n g " which were d i s t i n g u i s h a b l e from the s c i e n t i f i c concept since few s c i e n t i f i c c h a r a c t e r i s t i c s were used.  This supports Looft's (1974) f i n d i n g s that  many p u p i l s have an incomplete understanding of l i v i n g according t o associated b i o l o g i c a l a t t r i b u t e s such as n u t r i t i o n , r e s p i r a t i o n , reproduction, e t c .  The concept of l i f e has important meaning i n the way  p u p i l s perceive b a c t e r i a t o f u n c t i o n i n the context of the two experiments s t u d i e s .  I t was a n t i c i p a t e d (1.31) that the p u p i l s ' conceptual framework of b a c t e r i a might i n f l u e n c e the p u p i l s ' understanding of the experimental content examined i n t h i s study. I f the experiments  are examined i n d e t a i l  i t can be seen that i n order f o r the p u p i l s t o i n t e r p r e t them c o r r e c t l y ,  -111-  p u p i l s need t o be able t o use a number of concepts that make up the conceptual framework of b a c t e r i a .  In both experiments p u p i l s need t o  appreciate that b a c t e r i a are widely d i s t r i b u t e d i n the environment i f they are  t o p r e d i c t the r e s u l t s of the i n v e s t i g a t i o n s . Most p u p i l s appreciated  that b a c t e r i a are widely d i s t r i b u t e d since most claimed the widespread existence of b a c t e r i a i n the i n i t i a l c l i n i c a l interview.  This idea i s  necessary f o r understanding the p o s s i b i l i t y of contamination o f the s t e r i l e p e t r i dishes and media used i n the experiments.  Another concept  required t o understand how contamination might occur i s that of b a c t e r i a being l i v i n g u n i t s . the  Of the seven supporting concepts that contribute t o  concept o f l i f e , that of reproduction i s the most fundamental t o these  experiments since i f reproduction does not occur, the b a c t e r i a do not become v i s i b l e as c o l o n i e s .  The concept of reproduction can be used t o  e x p l a i n the increase i n t h e s i z e o f b a c t e r i a l c o l o n i e s . P u p i l s may not be able t o d i f f e r e n t i a t e between the growth i n the s i z e of a b a c t e r i a l colony i n v o l v i n g many c e l l s and the growth taking place i n one c e l l .  For growth  to take place, whether i t be m u l t i c e l l u l a r i n terms o f colony growth or the  increase i n the s i z e of one c e l l , a source of food i s necessary. The  concept of n u t r i t i o n t o support growth and reproduction i n b a c t e r i a i s a p r e r e q u i s i t e concept t o understanding the l i v i n g nature of b a c t e r i a . Thus i t seems evident that p u p i l s are required t o have an understanding of a number of r e l a t e d concepts i n t h i s area before i t would be reasonable t o expect p u p i l s t o understand the two experiments i n t h i s study.  I f the p u p i l uses the term germ or b a c t e r i a i t places the p u p i l ' s mastery of the concept a t l e v e l one on KLausmeier's (1976) f i v e l e v e l s of mastery.  The a b i l i t y t o give meaning t o the concept by showing knowledge  -112-  of a l l the d e f i n i n g a t t r i b u t e s of the concept promotes concept mastery to l e v e l f i v e (Klausmeier, 1976).  Although a l l the a t t r i b u t e s of b a c t e r i a  are not required, b a c t e r i a l l i f e concepts are important i n understanding the  experiments i n q u e s t i o n . In order t o reach mastery l e v e l f i v e f o r the  concept of b a c t e r i a l l i f e the p u p i l would need t o c l a s s i f y instances of n u t r i t i o n , e x c r e t i o n , s e n s i t i v i t y , reproduction, growth and movement.  To  understand these experiments p u p i l s should have concepts of movement, reproduction, growth and n u t r i t i o n i n r e l a t i o n to b a c t e r i a .  From the  r e s u l t s obtained i t i s found that p u p i l s commencing these experiments do not r e l a t e concepts of movement, reproduction, growth and n u t r i t i o n to bacterial l i f e .  These appropriate concepts were held by only two p u p i l s  i n the c l a s s and these were held i n r e l a t i o n t o the general term " l i v i n g t h i n g s " and not s p e c i f i c a l l y t o b a c t e r i a .  Other p u p i l s did not possess  any understanding of b a c t e r i a as l i v i n g organisms.  In the i n i t i a l  interview p u p i l s were not asked about the c o n t i n u i t y of l i f e i n b a c t e r i a l c o l o n i e s , but Tamir et a l . (1981) reported that 45 % of h i s grade 5-9 sample of p u p i l s understood the c o n t i n u i t y of l i f e and 36 % r e a l i z e d that l i v i n g organisms o r i g i n a t e from other l i v i n g organisms.  This would be an  important concept to hold i f one were to ask the p u p i l s t o p r e d i c t the r e s u l t s of the f i r s t experiment.  This task would be u n r e a l i s t i c f o r the  p u p i l s since only one p u p i l had previously seen b a c t e r i a l c o l o n i e s .  The  i d e n t i f i c a t i o n of b a c t e r i a was not problematical f o r p u p i l s since they showed that they had basic ideas of s o r t i n g things according t o physical properties such as shape, s i z e , e t c . The a c q u i s i t i o n of s o r t i n g s k i l l s associated w i t h c l a s s i f i c a t i o n was most probably obtained i n the previous school year and r e i n f o r c e d w i t h everyday experiences. I t was also expected that p u p i l s would have a greater mastery of the concept of l i v i n g  -113-  since t h i s concept was taught i n the f i r s t year science s y l l a b u s .  P u p i l s approached the two experiments without, i n the researcher's view, s u f f i c i e n t s c i e n t i f i c conceptual knowledge to be able to make meaningful conclusions from the r e s u l t i n g data. type of s i t u a t i o n i s never intended by teachers.  The occurence of t h i s However, i n the  researcher's experience, t h i s cannot be unusual since i t was  the  researcher's expectation that p u p i l s would have reached higher l e v e l s of mastery i n the concept of l i f e as a r e s u l t of p r i o r l e a r n i n g experiences and only through the i n i t i a l interviews were the concepts of b a c t e r i a l l i f e found absent.  The researcher's f i n d i n g s confirm Tasker's C1981)  conclusions that p u p i l s ' knowledge s t r u c t u r e s , against which l e a r n i n g experiences occur, are frequently not the s t r u c t u r e s the teacher assumed p u p i l s had. This would seem t o compound p a t t e r n s of teaching new  concepts  since the " b u i l d i n g b l o c k s " of the concept may not be there or, i f present, possess d i f f e r e n t r e l a t i o n s h i p s than those possessed by the teacher.  In t h i s study remedial work was not embarked on and p u p i l s  commenced t o use t h e i r knowledge i n the two experiments.  The r e s u l t s of  the p u p i l s ' endeavours t o understand the two experiments are discussed i n the f o l l o w i n g s e c t i o n s .  5.2  Discussion of p u p i l s ' i n t e r p r e t a t i o n of the experiments i n the study This s e c t i o n describes the r o l e played by p u p i l s ' b e l i e f s as they  r e l a t e to the p u p i l s ' attempts t o i n t e r p r e t the experiments " B a c t e r i a i n the A i r " and "Bacteria on Ourselves".  These b e l i e f s were revealed during  the second and t h i r d c l i n i c a l interviews r e s p e c t i v e l y , which took place  -114-  a f t e r the p u p i l s had performed the experiments.  An account of these  b e l i e f s was presented i n Chapter Four of t h i s study.  In t h e i r  i n t e r p r e t a t i o n s of the f i r s t experiment the p u p i l s i l l u s t r a t e d that they were able to i d e n t i f y b a c t e r i a .  The concept of many b a c t e r i a l c e l l s  making up a colony seems t o be held by many p u p i l s . However, p u p i l s found i t d i f f i c u l t t o explain why the colonies varied i n s i z e .  P u p i l s were unsure of the purpose of the s t e r i l i z a t i o n procedure and the s i g n i f i c a n c e that possible unintended contamination through f a i l u r e of the s t e r i l i z a t i o n process may play i n obscuring the r e s u l t s . As a r e s u l t of the absence of these "ideas" i t was not s u r p r i s i n g that p u p i l s d i d not understand the s i g n i f i c a n c e of the c o n t r o l p l a t e since t h i s requires some understanding o f the s t e r i l i z a t i o n process.  In the second experiment i t was expected that the p u p i l s would use ideas generated from the f i r s t experiment and have a greater depth of understanding of the purposes of the s t e r i l i z a t i o n procedure and the r o l e of the c o n t r o l p l a t e .  In summary, p u p i l s provided uniform predicted  r e s u l t s f o r the second experiment.  The p u p i l s hypothesized that the  " d i r t y hands" p l a t e would have the most b a c t e r i a and a l l the p u p i l s predicted that the c o n t r o l p l a t e would be f r e e from b a c t e r i a l colonies. P u p i l s believed that contamination o f the plates was most l i k e l y t o come from the a i r r e s u l t i n g i n a mixture o f the airborne b a c t e r i a with b a c t e r i a obtained from p u p i l s ' hands. for more than a minute.  To prevent t h i s , the plates were not opened  However, i f airborne b a c t e r i a were l e t i n t o the  p e t r i d i s h p u p i l s thought that i t would be p o s s i b l e t o i d e n t i f y these from those from a p u p i l ' s hand by the colour of the b a c t e r i a .  A l l the p u p i l s  -115-  thought the s t e r i l i z a t i o n process was e f f e c t i v e and more p u p i l s were aware that knowing the s t e r i l i z a t i o n process was successful was important. These l a t t e r p u p i l s offered methods of s u b s t a n t i a t i n g the s t e r i l i t y of the equipment.  However, many p u p i l s s t i l l expected that proof of  s t e r i l i z a t i o n could be obtained immediately a f t e r the s t e r i l i z a t i o n procedure.  A l l p u p i l s stated that the c o n t r o l plate would be f r e e from  b a c t e r i a , but some p u p i l s s t i l l believed that b a c t e r i a would be able to seep i n t o the p e t r i dishes through the "gap" between the l i d and the base. Only two p u p i l s claimed that the purpose of the c o n t r o l p l a t e was t o t e s t the i n i t i a l s t e r i l i t y of the plates and that t h i s plate could also show that b a c t e r i a were not seeping i n t o the p e t r i dishes.  5.21  Analysis of the concepts required t o understand the experiments In both experiments p u p i l s were required t o i d e n t i f y b a c t e r i a l  colonies on the agar i n order to obtain experimental data.  Before  experiment one "Bacteria i n the A i r " most p u p i l s had not had any previous experience i n i d e n t i f y i n g b a c t e r i a and so could not r e l y on t h e i r p r i o r b e l i e f s to a s s i s t them i n i d e n t i f i c a t i o n .  However, p r i o r b e l i e f s about  b a c t e r i a could be used i n the j u s t i f i c a t i o n of the growth of colonies and the spread of b a c t e r i a on the p l a t e s .  Concepts may influence the p u p i l ' s view of the s c i e n t i f i c procedures used i n both experiments. The important s c i e n t i f i c procedures are the s t e r i l i z a t i o n process and the r o l e of the c o n t r o l p l a t e .  Concepts of  b a c t e r i a l l i f e are required i n order to understand these two features. To understand the necessity f o r s t e r i l e media and equipment the word s t e r i l e must have meaning f o r the p u p i l .  The s c i e n t i s t would immediately  -116-  conclude that the medium d i d not contain any l i v i n g micro-organisms. L i v i n g organisms would be regarded as those that f u l f i l l the seven characteristics of l i f e .  P u p i l s should a l s o appreciate that any form o f  l i f e on the agar would be regarded as contamination and r e s u l t i n u n s t e r i l e conditions.  Therefore, understanding the contamination o f the  agar and the p e t r i dishes requires the p u p i l t o have concepts about bacterial l i f e .  I f there i s contamination from the agar the s c i e n t i s t  would recognize that the agar provides n u t r i e n t s t o support l i f e . Evidence that the b a c t e r i a on the plates are l i v i n g i s provided by the growth of colonies on the agar.  The idea of growth of a colony by c e l l  d i v i s i o n i s an e s s e n t i a l subsumer concept i n the concept of b a c t e r i a l life.  There i s also the p o s s i b l e contamination of s t e r i l e agar from u n s t e r i l e p e t r i dishes. S c i e n t i s t s understand that b a c t e r i a may spread onto the agar which provides support f o r l i f e .  The s t e r i l i t y o f the  medium, agar and the p e t r i d i s h i s important and i t i s necessary t o confirm t h i s i n order t o be able t o s t a t e from which sources the b a c t e r i a on the plate were obtained from.  I f s t e r i l i z a t i o n preparations are  performed s a t i s f a c t o r i l y the unopened c o n t r o l plate can prove the required s t e r i l i t y o f the equipment and media.  The underlying r o l e s played by a v a r i e t y o f concepts r e l a t e d t o the l i f e of b a c t e r i a has been discussed, i t i s now necessary t o look a t how the p u p i l s ' concepts o f b a c t e r i a l l i f e influence t h e i r i n t e r p r e t a t i o n o f the experiments.  -117-  5.22  Pupils' prior beliefs  5.221  I d e n t i f i c a t i o n of b a c t e r i a P u p i l s had to i d e n t i f y b a c t e r i a on the agar i n order to obtain  experimental data.  I d e n t i f i c a t i o n of b a c t e r i a requires the p u p i l to  c o r r e c t l y assign the organism to a d i s t i n c t group.  P u p i l s were able to  i d e n t i f y d i f f e r e n t types of b a c t e r i a from the agar by the colour of the colonies.  In the i n i t i a l interview p u p i l s d i d not use the c r i t e r i o n of  colour f o r i d e n t i f i c a t i o n of d i f f e r e n t b a c t e r i a .  Eight out of thirty-one  p u p i l s i n the i n i t i a l c l i n i c a l interview used shape to d i f f e r e n t i a t e between the d i f f e r e n t b a c t e r i a before; they had a c t u a l l y seen any examples of b a c t e r i a .  When i t becomes apparent that the microscopic world of  bacteria i s smaller than p u p i l s previously imagined shape as a c r i t e r i o n between d i f f e r e n t b a c t e r i a l o s e s i t s appeal. Students were able to see  the  l i m i t a t i o n s of the concept of shape to s o r t b a c t e r i a i n t h i s s i t u a t i o n and s u b s t i t u t e d the c r i t e r i o n of shape f o r another c r i t e r i o n that would allow v i s u a l data to be more manageable. They used colour to separate b a c t e r i a that may was  be on p u p i l s ' hands from b a c t e r i a obtained from the a i r .  suggested by p u p i l s interviewed  asked how  This  a f t e r the second experiment who were  i t was p o s s i b l e to d i f f e r e n t i a t e between b a c t e r i a obtained from  sources such as the a i r , the agar, or from the hands.  Their answer was  probably enhanced by the v a r i e t y of coloured colonies v i s i b l e on the plates used i n the previous experiment.  Coloured colonies may  have  detered p u p i l s from using the c o n t r o l plate to detect contamination from u n s t e r i l e agar.  -118~  5.222  The concept o f b a c t e r i a l colony  A n a l y s i s of t r a n s c r i p t s showed that p u p i l s were able t o e x p l a i n the concept of a b a c t e r i a l colony i n terms of the colony being made up .of many bacteria.  Although p u p i l s were able t o describe a b a c t e r i a l colony, they  were unable t o e x p l a i n why the c o l o n i e s v a r i e d i n s i z e . P u p i l s used t h e i r concepts of growth and reproduction, but they d i d not have s u f f i c i e n t mastery of these concepts t o allow themselves any p r o f i t a b l e i n s i g h t t o e x p l a i n why colonies v a r i e d i n s i z e .  For example, Jonathon was unable t o  e x p l a i n why some of the c o l o n i e s were l a r g e r than others. interview reveals that he perceives b a c t e r i a as l i v i n g .  His i n i t i a l He supported h i s  statement with b e l i e f s that b a c t e r i a feed on blood and t h a t chemicals them.  kill  However, these are not concepts that can support an argument f o r  d i f f e r e n t colony s i z e s .  Another p u p i l , Steven, who had only one reason  for b a c t e r i a being a l i v e was able t o give a l o g i c a l reason t o e x p l a i n the d i f f e r e n t s i z e s of the c o l o n i e s . Steven's concept consisted o f b a c t e r i a reproducing themselves  every twenty minutes. This was a u s e f u l conceptual  springboard that enabled the question about varying colony s i z e s t o be answered. P h i l i p also used h i s concepts revealed i n the f i r s t  clinical  i n t e r v i e w t o answer t h i s q u e s t i o n . A v i s i t t o the d e n t i s t had r e s u l t e d i n a d i s c u s s i o n about tooth decay.  P h i l i p revealed t h a t b a c t e r i a "grow and  s i t and m u l t i p l y i n the t e e t h " .  He used h i s l i f e concept of b a c t e r i a  m u l t i p l y i n g t o e x p l a i n that b a c t e r i a could spread a l l over the agar. Concepts of b a c t e r i a l l i f e can achieve greater s t a b i l i t y and be incorporated i n t o broader conceptual frameworks i f they are able t o provide acceptable explanations t o questions.  The explanations about b a c t e r i a l colony s i z e appear t o be r e l a t e d t o  -119-  *  how the p u p i l s view the l i f e functions of the b a c t e r i a .  Bacterial l i f e  concepts are important since the s i z e of the c o l o n i e s i s r e l a t e d t o the r e p r o d u c t i v e f u n c t i o n of the b a c t e r i a . I n t h e present study i t would seem that many p u p i l s do not have s u f f i c i e n t knowledge of these l i f e concepts to be able t o r e l a t e t h e i r b e l i e f s t o the observations made i n the experiment.  I t i s postulated that the concept of b a c t e r i a l l i f e i s  necessary i n order t o understand the spread o f b a c t e r i a l colonies on the agar.  5.223  P u p i l s ' concept of s t e r i l i z a t i o n  The a p p l i c a t i o n of b a c t e r i a l l i f e concepts and i n p a r t i c u l a r those of growth and reproduction t o support the s i g n i f i c a n c e of s t e r i l i z a t i o n of the agar and the p e t r i dishes i s e s s e n t i a l .  From the a n a l y s i s of answers  to questions i n the three c l i n i c a l interviews there appears t o be three categories o f p u p i l s .  The l a r g e s t group of p u p i l s consists o f those  p u p i l s who do not hold l i f e concepts r e l a t e d t o b a c t e r i a and cannot support t h e i r reasons f o r claiming the success of the s t e r i l i z a t i o n process. The second group possessed l i f e concepts but d i d not use them; the smallest group held the b a c t e r i a l l i f e concepts of reproduction and used them t o produce a v a l i d argument f o r the proof of the s t e r i l i z a t i o n procedure being s u c c e s s f u l .  In the f i r s t experiment p u p i l s who could not g i v e adequate reasons t o s u b s t a n t i a t e the success of t h e s t e r i l i z a t i o n procedure were found t o have no concepts o f b a c t e r i a l l i f e .  Their reasoning included the assumption  that because the s t e r i l i z a t i o n procedure had been performed, then i t was n a t u r a l l y a success. However, a l l these p u p i l s d i d a p p r e c i a t e . t h e reasons  -120-  for  sterilization.  Perhaps more i n t e r e s t i n g are the s p e c u l a t i v e reasons as t o why p u p i l s of the second group did not use t h e i r p r i o r concepts of b a c t e r i a l l i f e . Nicole was one of these p u p i l s .  Nicole's p r i o r b e l i e f s about the l i f e  functions o f b a c t e r i a included a statement that b a c t e r i a were l i v i n g because they could be seen growing.  The concept of growth i n colonies o f  b a c t e r i a i s required i n order t o reason about s t e r i l i z a t i o n .  To  substantiate that the plates were s t e r i l e the p u p i l would have t o understand the meaning o f the word s t e r i l e .  This would also e n t a i l  recognizing t h a t since the c o n t r o l p l a t e was not opened there would not be any growth of b a c t e r i a i f the agar and p e t r i d i s h were s t e r i l e .  I t would  be expected t h a t N i c o l e ' s concept of growth would have helped her with the proof of s t e r i l i z a t i o n .  She wanted t o check f o r contamination of the  plates by examining the agar with a microscope t o see i f there were any bacteria.  She may have been under the impression that growing b a c t e r i a  can only be observed by using a microscope.  The worksheet provided f o r  the experiment stated that colonies o f b a c t e r i a would e a s i l y be v i s i b l e t o the naked eye a f t e r a few days.  A n a l y s i s of the group work t r a n s c r i p t  showed that Nicole and her work colleagues had not read a l l the i n s t r u c t i o n s t o the experiment before commencing, thereby missing an important piece of information.  Nicole appreciated that contamination  could come from the a i r and also from unwashed hands but d i d not record that b a c t e r i a may come from the equipment,  Nicole speculated that since  the c o n t r o l p l a t e was unopened, contamination may be occuring through the "gap" between the l i d of the p e t r i dishes and t h e i r bases and that the c o n t r o l p l a t e would t e s t f o r t h i s .  In another example, Steven's l i f e  -121-  concepts supported him i n h i s concept of s t e r i l i z a t i o n , k i l l i n g the b a c t e r i a i n the p e t r i dishes and r i d d i n g the plates of unwanted b a c t e r i a . However, he d i d not use h i s concept that included ideas o f b a c t e r i a l c e l l s d i v i d i n g t o prove that the plates were s t e r i l e because the c o n t r o l p l a t e was f r e e from b a c t e r i a .  Like Nicole he also though the the c o n t r o l plate  would i n d i c a t e i f b a c t e r i a were seeping through the gap or even the g l a s s .  P u p i l s l e a r n t from the f i r s t experiment that b a c t e r i a are widespread i n the a i r and that these b a c t e r i a could be grown on the agar. p u p i l s appreciated  Most  that there could be contamination o f the plates by  b a c t e r i a from unwanted sources.  However, few suggested that the agar and  the p e t r i d i s h could s t i l l be contaminated a f t e r s t e r i l i z a t i o n i f the process had not been completed properly.  Only two p u p i l s viewed the agar  as a source of food but neither of these p u p i l s claimed that the agar should be s t e r i l i z e d along with the glass p e t r i d i s h .  I t appears that  p u p i l s d i d not connect the agar with any concept of l i f e and therefore no r e a l need f o r s t e r i l i z a t i o n was seen. I t i s more understandable that p u p i l s do not regard the p e t r i dish as a source of contamination since i t i s not an obvious food source.  In the second experiment three p u p i l s provided a s c i e n t i f i c reason f o r the success of the s t e r i l i z a t i o n process.  They d i d so by using t h e i r  concepts of b a c t e r i a l l i f e which other p u p i l s d i d not possess.  Two of  these p u p i l s argued that the c o n t r o l p l a t e was used t o prove the s t e r i l i t y of the p l a t e s before the experiment s t a r t e d . Nichola argued t h a t b a c t e r i a would not grow on the plates i f the p l a t e s were s t e r i l e but d i d not r e l a t e t h i s proof of s t e r i l i t y t o the f u n c t i o n of the c o n t r o l p l a t e . Many of the  -122-  p u p i l s showed i n t h e i r w r i t t e n work that they could not e s t a b l i s h i f the agar and the p e t r i dishes were s t e r i l e a t the beginning o f the experiment and possessed a l t e r n a t i v e perceptions o f the c o n t r o l p l a t e than those that would normally be held by the s c i e n t i s t .  5.224  P u p i l s ' perceptions o f the r o l e o f the c o n t r o l p l a t e  Most p u p i l s viewed the r o l e of the c o n t r o l plate as a comparison against other p l a t e s .  Some p u p i l s used i t t o check i f any b a c t e r i a had  entered the plate through the "gap" between the l i d and the base. The construction o f the plates may have contributed t o the ideas held by many pupils.  In everyday l i f e the seal o f a j a r i s expected t o be t i g h t i f  t h i n g s are to be kept i n o r out. The glassware of the p e t r i d i s h i s loose f i t t i n g and may give the impression that a seal was absent. the p u p i l s had the opportunity  However, a l l  t o prove that b a c t e r i a were not entering  the p l a t e s by t h i s method because a t the end o f the experiment the c o n t r o l plate was free from b a c t e r i a .  Only M i c h e l l e used t h i s evidence t o argue  against the notion o f b a c t e r i a seeping i n .  Seven o f the nine p u p i l s interviewed  i n the second experiment could  not provide a proof o f s t e r i l i z a t i o n and the c o n t r o l p l a t e was s t i l l viewed as a comparison between other p l a t e s .  The p u p i l s with adequate  b a c t e r i a l l i f e concepts concerned with reproduction  or growth, a t a  m u l t i c e l l u l a r l e v e l , were able t o j u s t i f y t h e i r reasoning f o r the s t e r i l i z a t i o n process and the c o n t r o l p l a t e . concepts those o f reproduction d i v i s i o n were the most u s e f u l .  Of the b a c t e r i a l l i f e  or growth concepts with reference t o c e l l Some p u p i l s added t o t h e i r concepts  through doing the experiment, but they often d i d so i n a l e s s than  -123-  s a t i s f a c t o r y way because these newly acquired concepts could not be used to generate the s c i e n t i f i c meaning f o r the procedures used i n the experiment. "A c h i l d who has r e a l l y learned something can use i t , and does use i t . i t i s connected with r e a l i t y i n h i s mind, therefore he can make other connexions between i t and r e a l i t y when the chance comes. A piece of unreal l e a r n i n g has no hooks on i t : i t can't be attached t o anything, i t i s no use t o the l e a r n e r " (Holt, 1975, p. 104).  Experiments may change the r e l a t i o n s h i p between concepts or add new concepts t o conceptual frameworks but not necessarily i n accordance with the s c i e n t i f i c a l l y preferred meaning.  The environment beyond school  provides p u p i l s with a r i c h source of concepts that may be i n t e r p r e t e d i n d i f f e r e n t ways but we cannot guarantee that these new concepts are i n t e r p r e t e d i n the same way as s c i e n t i s t s would i n t e r p r e t them  5.3  P u p i l held concepts a f f e c t i n g the understanding of the experiments This section w i l l examine the e f f e c t that the concepts of s t e r i l i t y  and growth have on a p u p i l ' s understanding of the experiment.  The nature  of these concepts may hinder or a i d the p u p i l ' s understanding of the procedures used i n the experiments s t u d i e s .  5.31  P u p i l s ' concept of s t e r i l e At the beginning o f the experiment p u p i l s received an explanation  about how the s t e r i l i z a t i o n process was performed.  In t r a n s c r i p t s from  c l i n i c a l interviews most p u p i l s showed that they understood the meaning of s t e r i l e i n the context of the experiment.  However, i t was found that  a l t e r n a t e views of the meaning of s t e r i l e d i d a l t e r p u p i l s ' perceptions  -124-  of the experiment.  Nichola provides an example of an a l t e r n a t e perception of the experiment.  She began the two experiments with no evidence of concepts  r e l a t e d to the l i f e o f b a c t e r i a .  Her homework revealed that a f t e r  experiment one she could not provide evidence that the s t e r i l i z a t i o n process was s u c c e s s f u l .  In the second experiment Nichola suggested that  the c o n t r o l p l a t e acted as a comparison showing the d i f f e r e n c e between the plates that had b a c t e r i a on them and the p l a t e that d i d not have any b a c t e r i a on i t at a l l . In the second c l i n i c a l i n t e r v i e w Nichola suggested using a microscope to check i f tine plates were s t e r i l e . suggested p u t t i n g the p l a t e s i n a s t e r i l e room.  Later she  Nichola claimed  that  anything that was s t e r i l e would stop b a c t e r i a growing and that the plates were s t e r i l e i f they were not d i r t y . She suggested t h a t i n some instances the agar might not be s t e r i l e so then the b a c t e r i a would grow on the agar. Nichola thought that the plates had b a c t e r i a on them because none were placed i n a s t e r i l e room.  She stated that a warm room (or incubator)  would have more b a c t e r i a i n i t . I t i s i n f e r r e d that the need f o r a s t e r i l e room suggests that she believes that the b a c t e r i a are c o n t i n u a l l y g e t t i n g i n t o the p l a t e . I f they d i d and the agar was " s t e r i l e " ,  according  t o N i c h o l a s meaning o f the word, then the b a c t e r i a would not grow because 1  the agar would not support growth.  Nichola*s concept of s t e r i l i t y consisted of b a c t e r i a being on the p l a t e but not growing because the agar was s t e r i l e . This i s not compatible w i t h the s c i e n t i s t s ' view of s t e r i l i t y but can be used t o support the r o l e of the c o n t r o l p l a t e i n a l i m i t e d context.  Nichola would t h i n k that  -125-  p l a t e C was s t e r i l e as she claimed i n her interview, but she would not be able t o use t h i s information t o confirm that the other p l a t e s were sterile.  The inadequacies of her argument perhaps a r e obscured because the  other p l a t e s are innoculated using b a c t e r i a from p u p i l s ' hands and p u p i l s are attempting t o prevent contamination form the a i r . Nichola not only appears t o have an unstable concept o f s t e r i l i t y because she cannot decide i f s t e r i l e means t o prevent growth (which could come from the human reproduction sense) or t o be without l i f e , but she also perceives the experiment i n d i f f e r e n t terms by presumably t h i n k i n g that b a c t e r i a can get i n t o the plates from outside. Other p u p i l s who view b a c t e r i a seeping i n t o the p l a t e may also hold Nichola's concept of s t e r i l i t y and therefore can s t i l l reason why the c o n t r o l p l a t e was not contaminated w i t h b a c t e r i a a f t e r each experiment.  . 5.32  P u p i l s ' concept o f growth P u p i l s acquire concepts from many d i f f e r e n t sources, e.g. watching  t e l e v i s i o n , l i s t e n i n g t o other people's ideas, doing  experiments.  Sometimes these concepts are stored i n long term memory and used again only when appropriate l i n k s can be made t o new incoming information (Freyberg and Osborne, 1981).  I f these p r i o r concepts can be used and  they provide new i n s i g h t i n t o a novel s i t u a t i o n , then they could act as b u i l d i n g blocks t o f u r t h e r concept development.  In some other instances  concepts may be inappropriately l i n k e d t o aspects o f new information and therefore become stumbling blocks t o f u r t h e r concept development.  From a n a l y s i s of the data provided by c l i n i c a l i n t e r v i e w three, three p u p i l s had concepts of b a c t e r i a l growth but d i d not use them.  One of  -126-  these p u p i l s learned about b a c t e r i a l growth from watching a t e l e v i s i o n program.  Her growth concept was based on watching b a c t e r i a being plated  on agar and put i n the r e f r i g e r a t o r t o grow. the  Since the circumstance of  c l a s s experiments were d i f f e r e n t (an incubator was used), Sharon was  unable t o make an appropriate l i n k w i t h her growth concepts o f b a c t e r i a present i n long term memory. Sharon's concept map possessed the most b a c t e r i a l l i f e concepts compared t o other p u p i l s but some of these concepts were the r e s u l t of misinterpreted information. now hindered comprehension o f the experiment.  These concepts  Two other p u p i l s who used  concepts of b a c t e r i a l growth developed t h e i r concepts during the course of the  experiments because they were not evident i n the i n i t i a l interview.  I t seems that p u p i l s who have come t o the experimental s e t t i n g with few previous ideas about b a c t e r i a cannot achieve an understanding of the r e s u l t s and purpose of the experiment.  At an elementary l e v e l there are two r e l a t e d b e l i e f s that can be held concerning b a c t e r i a l growth - that of an increase i n i n d i v i d u a l c e l l s i z e or that of c e l l d i v i s i o n t o increase the numbers of c e l l s i n a colony and so increase the s i z e of the colony.  I f p u p i l s state that b a c t e r i a grow  and become v i s i b l e on the plate t h i s statment does not reveal which concept of growth the p u p i l i s using.  I t i s speculated that p u p i l s who  use the concept of the b a c t e r i a l c e l l enlarging w i l l not be able t o make as much use of t h i s concept as the p u p i l who believes t h a t the b a c t e r i a l c e l l can undergo c e l l d i v i s i o n and produce a r e p l i c a of i t s e l f .  This  l a t t e r concept can be used t o e x p l a i n the large numbers o f b a c t e r i a present i n the a i r and the p o t e n t i a l source of b a c t e r i a from one b a c t e r i a l c e l l present i n the u n s t e r i l e agar.  -127-  I t i s speculated that p u p i l s who do not use t h e i r concept of growth i n t h e i r explanations perceive the concept o f growth, r e l a t e d t o b a c t e r i a , as an increase i n c e l l s i z e .  This concept can be r e l a t e d t o everyday  l i f e , p u p i l s observe t h e i r brothers and s i s t e r s growing withouth the notion o f c e l l d i v i s i o n - the organisms simply become bigger.  5.33  The influence of concepts on problem s o l v i n g Chapter Two speculated that d i f f i c u l t i e s with problem s o l v i n g could  be the r e s u l t of the l a c k o f linkages or inadequate knowledge structures t h a t p u p i l s possess. P u p i l s are o f t e n unable t o connect t h e i r meaning o f the problem t o t h e i r knowledge s t r u c t u r e s ,  constructed  many of the p u p i l s  interviewed f o r t h i s study had inadequate knowledge structures about the concept of " l i v i n g " t o be able t o apply these concepts t o prove the success of the s t e r i l i z a t i o n procedure and e x p l a i n the r o l e of the c o n t r o l plate.  Osborne and Wittrock (1983) observed that p u p i l s had d i f f i c u l t y  with s t a r t i n g the problem. I f as Case (1974) suggests, p u p i l s chunk t h e i r sensory information, they could begin the problem by asking themselves "why does b a c t e r i a grow on a l l but one of the agar p l a t e s ? "  Their  reasoning pattern t o solve t h i s question f o r the f i r s t experiment, using Case's a n a l y s i s , could be chunked i n t o s a l i e n t information u n i t s such as: 1)  Why does b a c t e r i a grow on a l l but one of the plates?  2)  I t could be that the a i r l e t i n t o a l l but one p l a t e had b a c t e r i a .  3)  I t could be that the agar was not s t e r i l e at the beginning.  4)  I f the agar used was the same i n a l l the plates i t can't be the agar.  -128-  P u p i l s do not ask themselves t h i s f i r s t question but never the l e s s p u p i l s do produce the second statement i f they do not b e l i e v e that b a c t e r i a are seeping i n t o the p l a t e .  However, many p u p i l s do not produce  the t h i r d informational u n i t since most take f o r granted the success of s t e r i l i z a t i o n and do not question the s t e r i l i t y of the agar. To check the s t e r i l i t y of the agar some p u p i l s suggested that a microscope could be used.  P u p i l s appreciated that b a c t e r i a were microscopic but d i d not  appreciate that the use o f the microscope would only confirm b a c t e r i a being there and not that they were l i v i n g or growing.  Only a concept of  growth i n terms o f b a c t e r i a l c e l l d i v i s i o n would generate meaning f o r the p u p i l and help e x p l a i n the exponential increase of b a c t e r i a l c e l l s i n the colonies that r e s u l t s i n the b a c t e r i a being e a s i l y v i s i b l e .  Pupils  without concepts of c e l l d i v i s i o n are hindered i n obtaining proof of the s t e r i l i z a t i o n process. three s a l i e n t .  This proof i s required t o make information u n i t  Robert and P h i l i p could reason through the four  information items since they had shown i n t h e i r i n i t i a l interview that they had concepts o f reproduction and growth that allowed them t o make the information items s a l i e n t .  Both reached the correct conclusion as t o the  r o l e of the c o n t r o l p l a t e .  Steven and N i c o l e d i d not use t h e i r concepts of l i f e t o r a t i o n a l i z e the r o l e of the c o n t r o l plate and could not reach a conclusion because t h e i r concept of the sources of contamination statement made i n information item two.  could not support the  In t h e i r view a i r may have been  l e t i n t o a l l of the p l a t e s because of the "gap" between the p e t r i d i s h l i d and the base.  I n t h i s instance the perceived p h y s i c a l nature of the  experiment may be more powerful than the concept of b a c t e r i a l l i f e i n  -129-  determining the success i n providing a reason f o r the r o l e of the c o n t r o l plate.  In t h i s s e c t i o n we have concluded that concepts of b a c t e r i a l l i f e play an important r o l e i n the understanding of the experiment.  The l e v e l  of mastery of these concepts i s important since the experiments demand that the p u p i l i d e n t i f i e s instances when the concept of growth and reproduction are relevant.  I f p u p i l s do not view the l i f e of b a c t e r i a  using concepts of growth and reproduction then the whole point of the experiment becomes meaningless.  I n some cases a l t e r n a t i v e concepts are  used i n the i n t e r p r e t a t i o n of the experimental data. T h i s i s demonstrated when p u p i l s view the b a c t e r i a i n f i l t r a t i n g the seal of the p l a t e .  For  the teacher, p r e r e q u i s i t e knowledge of the p u p i l s * p r i o r b e l i e f s  about b a c t e r i a i s e s s e n t i a l i n order that any e f f e c t i v e l e a r n i n g be encouraged.  P u p i l s are able t o modify t h e i r frameworks through  experimental tasks but i n many instances, t h e i r frameworks o f concepts s t i l l remain inadequate i n providing meaning f o r the experiments.  5.4  Discussion o f group work ( w r i t t e n answers) P u p i l s produced answers t o the questions displayed i n Appendix E f o r  experiments one and two. These q u e s t i o n s were intended t o provide d e t a i l s of the substantive b e l i e f s held by the c l a s s about the sources o f contamination, s t e r i l i z a t i o n procedure, and the r o l e of the c o n t r o l p l a t e .  A n a l y s i s revealed that p u p i l s perceived s t e r i l i z a t i o n as a means of disposing of any b a c t e r i a thay may have been on the p l a t e s p r i o r t o the  -130-  experiment.  The s t e r i l i z a t i o n of the agar appeared t o p u p i l s to have  l i t t l e relevance to the experiment since b a c t e r i a from the a i r or hands were considered  as more probable contaminants.  once the s t e r i l i z a t i o n procedure was  Few p u p i l s believed that  complete, u n i n t e n t i o n a l contamination  could occur from w i t h i n the p l a t e s . Some groups b e l i e v e d t h a t the c o n t r o l p l a t e was  part of the experimental design so that p u p i l s could compare the  differences between a l l the plates while others thought that the c o n t r o l plate held no purpose.  Another group, who believed that b a c t e r i a could  seep under the p e t r i d i s h l i d s , thought that the c o n t r o l plate designed to t e s t i f t h i s happened.  was  This hypothesis f o r the r o l e of the  c o n t r o l p l a t e was more popular i n the second experiment although the f i r s t experiment could have provided evidence to the p u p i l s that b a c t e r i a could not seep i n t o the d i s h . P u p i l s attempted to generate more meaning f o r the second experiment by a c t i v e l y t h i n k i n g about the reasons f o r the s t e r i l i z a t i o n process and proof for i t s success, rather than accepting that once the technique i s completed i t i s a success.  The c o n t r o l p l a t e  became u s e f u l i n various ways rather than having no purpose i n the experiment.  These changes i n viewpoint may  have been influenced by the  continued i n c l u s i o n of these processes i n the second experiment and  the  repeated questeions asked about s t e r i l i z a t i o n and the c o n t r o l plate a f t e r each experiment.  Written work provided by groups i s s i m i l a r to w r i t t e n work provided by i n d i v i d u a l s f o r an exercise a f t e r the experiment.  From w r i t t e n work  the teacher can obtain a sense of the b e l i e f s held by p u p i l s . However, as an assessable  piece of work i t has l i m i t e d use. Take f o r example question  number 7 on the question sheet "Bacteria on Ourselves" (Appendix E ) ,  "why  -131-  are the plates placed i n a warm incubator?"  Seven groups out of nine  believed that b a c t e r i a grow i n the warm incubator.  Of those seven groups  only one group mentioned that apart from growing, the b a c t e r i a w i l l reproduce, or i n the p u p i l ' s term "breed".  Some of the groups j u s t i f y  t h e i r reasons f o r t h e i r answers, but from t h e i r j u s t i f i c a t i o n s we s t i l l have a l i m i t e d idea about the p u p i l s ' concepts of growth. Written answers are u n l i k e l y t o reveal s u f f i c i e n t information about the extent of p u p i l s ' concepts.  Teachers assume that p u p i l s know the meaning and i m p l i c a t i o n s  of the words they use i n w r i t t e n work.  On these assumptions teachers  assess and categorize p u p i l s as having learned or not learned the desired concepts.  The w r i t t e n questions and answers were useful i n t h i s study as i n d i c a t o r s t h a t b e l i e f s revealed i n the c l i n i c a l interviews by some p u p i l s also r e f l e c t e d the b e l i e f s held by other c l a s s members. researcher  However, the  i s not able to assess the p u p i l s ' mastery of the concept t o the  same extent as i n the c l i n i c a l interview.  P u p i l s with a more  comprehensive understanding of the growth of b a c t e r i a would be able t o d i s t i n g u i s h between the growth of i n d i v i d u a l b a c t e r i a and the growth of bacterial colonies.  This i n s i g h t i n t o p u p i l generated meaning i s only  apparent i f one i n v e s t i g a t e s the p u p i l s ' substantive b e l i e f s by using more i n depth probing measures such as interviews rather than w r i t t e n questions.  This s e c t i o n reveals that s i m i l a r w r i t t e n assessment techniques used by teachers l a c k the sublety that i s required t o assess p u p i l performance i n laboratory w r i t t e n work.  Other methods o f assessment would be more  -132-  useful t o determine the conceptual understanding of the p u p i l s .  Section  5.7 reviews the problem of assessment of laboratory work.  5.5  Perceptions o f experimental tasks The perceptions that c h i l d r e n hold of the two experimental tasks  i n v e s t i g a t e d were obtained from t r a n s c r i p t s of group work produced by twelve p u p i l s .  The a n a l y s i s o f the t r a n s c r i p t s revealed that p u p i l s d i d  not read a l l the i n s t r u c t i o n s t o the experiment and instead of summarizing the procedure the groups were more content t o use a r e c i p e - f o l l o w i n g technique t o set up the experiment.  This confirms a tendency that Tasker  (1981) has discovered i n h i s research. Experimental tasks i n most schools are performed i n small groups and i t was noted that the s t r u c t u r e of the group influenced the perception that p u p i l s had o f the experiment. P r a c t i c a l work was seen as "assessable" by most groups and consequently the d i s c u s s i o n of questions t o be answered was seen as more important  than  r e f l e c t i o n on the s c i e n t i f i c procedures being used i n the experiment. This assessable nature of school work r e i n f o r c e d the p u p i l s ' a t t i t u d e that answers were required t o f u l f i l l the task o f the l e s s o n .  Pupils'  perceptions are r e l a t e d t o the i n s t r u c t i o n s of the experiment, that are required and the r e s u l t s being observed.  the a c t i o n s  Consideration of these  perceptions i s important when i n v e s t i g a t i n g p u p i l s ' experimental work since these may influence the change i n conceptual r e l a t i o n s h i p s w i t h i n a p u p i l ' s framework.  The method by which the two groups embarked on the f i r s t p r a c t i c a l task influenced the l a t e r d i s c u s s i o n of t h e i r r e s u l t s . read a l l the i n s t r u c t i o n s .  The boys d i d not  Although t h i s may have saved time, i t  -133-  prevented them from r e f l e c t i n g on the purpose of each stage of the experiment.  I t also required the p u p i l to take one informational item at  a time and r e f l e c t on that i n i s o l a t i o n and perform that i n s t r u c t i o n without any r e l a t i o n s h i p to the others.  Because the boys d i s t r i b u t e d the  plates among each other, and appeared t o place one p u p i l responsible f o r each p l a t e , they l o s t s i g h t of the o v e r a l l s t r u c t u r e of the experiment.  The choice not to read the whole of the i n s t r u c t i o n sheet at one time meant that when they reached i n s t r u c t i o n number seven they probably "After two days..." and thought that that piece of information redundant at the time.  read  was  In f a c t i t held an important concept i . e . that  b a c t e r i a w i l l grow i n colonies and that a f t e r two days they w i l l be v i s i b l e to the naked eye.  The l a c k of t h i s information meant a d i f f e r e n t  perception of the r e s u l t s and that Steven's query, concerning i f you could see the b a c t e r i a growing immediately or not, was ignored and thought irrelevant.  A more subtle reason may  be that i f they ignored t h i s query  they could answer the question about predicted r e s u l t s by looking at the dust marks (produced on the plates by the wind) that they mistook f o r bacteria.  This was f a r simpler than t r y i n g to r e f l e c t on t h e i r actions  and p r e d i c t an outcome.  By t a k i n g a recipe-type approach to the experiment a l l p u p i l s avoided a c t i v e l y generating r e l a t i o n s h i p s between the d i f f e r e n t aspects of the information i n the experiment. understanding instantaneous.  As we have seen, p u p i l s had problems  that the r e s u l t s of the experiment would not be This information was a v a i l a b l e to a l l p u p i l s i n the  i n s t r u c t i o n s of the experiment and could have been used by the p u p i l s to  -134-  construct t h e i r own information and draw inferences.  The procedure of  p u t t i n g p l a t e s i n the incubator and w a i t i n g f o r two days could have confirmed t h i s information, but instead, t h i s was neither considered nor connected t o the information provided and so was not f u l l y understood.  The second experiment used s i m i l a r s c i e n t i f i c procedures so i t would be expected that the experience of the f i r s t experiment would a i d the performance of the second p r a c t i c a l task.  This experience apparently d i d  help since the p u p i l s were not so i n t e n t on f o l l o w i n g the i n s t r u c t i o n s step by step. I t was not p o s s i b l e t o determine i f the p u p i l s r e s t r u c t u r e d the experiment t o see the task according t o t h e i r own framework since t h i s was not v e r b a l i z e d and recorded by p u p i l s .  In many cases the "discussions" about methods and r e s u l t s by the groups of p u p i l s d i d not involve p u p i l s i n a c t i v e l y l i s t e n i n g t o other members o f the group.  Neither d i d i t involve t e s t i n g other p u p i l s ' ideas  against t h e i r own framework.  There d i d not appear t o be any attempt t o  construct meaning from sensed experience and concepts stored i n long term memory.  I t was noticeable that i f one p u p i l i n the group was more  respected e i t h e r i n an academic or s o c i a l sense then his/her answers t o questions would be approved with l i t t l e r e f l e c t i o n .  The p r o v i s i o n of an  answer to questions appears t o be important and p u p i l s tend t o be more answer conscious than wanting t o share concepts that other p u p i l s supply or attempting t o generate l i n k s between new ideas and t h e i r own b e l i e f s . I t was a l s o seen as important t o f i n i s h the questions even i f the answers were not as s a t i s f a c t o r y t o the group as they could have been.  -135-  The g i r l s e x h i b i t e d the most s e n s i t i v e a t t i t u d e toward assessment. P r a c t i c a l l y everything that i s done i n schools tends t o make p u p i l s answer-centred  and the g i r l s i n p a r t i c u l a r showed t h i s by e d i t i n g t h e i r  tape of any d i s c u s s i o n passages.  The other group of g i r l s r e s t r i c t e d  t h e i r r e l e c t i o n of t h e i r potentional answers and showed an urgency t o f u l f i l l the task of answering the r e s t of the questions. that we as teachers are answer-centred  The chances are  and do not r e a l i z e the damage t h i s  does toward the p u p i l ' s a t t i t u d e of r e f l e c t i v e thought and how  this  centring can deter groups from l i s t e n i n g t o a l l i t s members reasoning. For example, i f the f i r s t speaker provides a good answer - i n that i t i s not too out of l i n e with the other p u p i l s ' frameworks - then t h i s can be found acceptable and there i s no need t o suggest, r e f i n e , or l i s t e n t o any other argument.  The manner i n which teachers present work, plus the  volume of work they assign can f o r c e p u p i l s i n t o these answer d i r e c t e d strategies.  Another problem i s t h a t i n general the p u p i l s do not see the  s e t t i n g up of an experiment as work.  R e f l e c t i n g back on my  own  experience, i f you take a l l of the lesson t o set up and discuss an experiment then p u p i l s w i l l often volunteer that they d i d not do any work In summary, i t would appear that p u p i l s tend t o avoid r e f l e c t i n g upon t h e i r own p h y s i c a l a c t i o n s , b e l i e f s and a t t i t u d e s .  This f i n d i n g , i n  combination w i t h the p u p i l ' s a t t i t u d e to p r a c t i c a l work and i t s assessment, should lead teachers t o r e v i s e t h e i r presentation of experiments so that p u p i l s become more problem centred and have an increased awareness of other p u p i l s ' viewpoints. Teachers need t o present problem o r i e n t a t e d tasks so t h a t i n s t r u c t i o n s , a c t i o n s and r e s u l t s can a l l be understood by generating new linkages t o concepts acquired through the experiment w i t h those already i n long term memory.  -136-  5.6  Conclusions This study reveals that p u p i l s possess a m u l t i p l i c i t y of b e l i e f s  concerning the existence and functions of b a c t e r i a .  The heterogeniety o f  b e l i e f s i s a r e s u l t of the v a r i e t y of subsuming concepts and the r e l a t i o n s h i p s of these subsuming concepts t o each other.  Prior beliefs  about b a c t e r i a were found t o influence the way p u p i l s perceive the experimental procedures involved i n the two experiments used i n t h i s investigation.  D i f f i c u l t i e s r e l a t e d t o e x p l a i n i n g colony s i z e revealed that p u p i l s possess d i f f e r e n t types of b e l i e f s f o r the concept of growth.  Those  p u p i l s who constructed growth concepts p r i m a r i l y i n terms of an increase i n c e l l s i z e had d i f f i c u l t y i n e x p l a i n i n g the reason f o r the v a r i e t y of colony s i z e s .  Those p u p i l s whose b e l i e f s about b a c t e r i a encompassed  growth concepts r e l a t e d t o c e l l d i v i s i o n were able t o explain colony growth w i t h greater c l a r i t y .  Many p u p i l s were not able t o provide more  than two c h a r a c t e r i s t i c s of b a c t e r i a l l i f e , but i t was found that i f they had a reasonably w e l l developed notion of growth which included c e l l d i v i s i o n or reproduction of b a c t e r i a t h i s was a s u f f i c i e n t basis f o r success i n i n t e r p r e t i n g the experiments.  P u p i l s appeared t o be unable to explain how t o show that the equipment was s t e r i l e .  Those p u p i l s appeared t o be "overloaded" w i t h the  p r a c t i c a l d e t a i l s ( i . e . nature of the p e t r i d i s h , e t c . ) of the experiment. Other p u p i l s , although possessing concepts of b a c t e r i a l l i f e , presented a l t e r n a t i v e b e l i e f s concerning the r o l e of the s t e r i l e equipment and medium.  Both p r a c t i c a l d e t a i l s of the experiment and a l t e r n a t i v e b e l i e f s  -137-  i n t e r f e r e d with the i n t e r p r e t a t i o n of the s i g n i f i c a n c e of the s t e r i l e equipment, medium and the s i g n i f i c a n c e of the c o n t r o l p l a t e s i n the  two  experiments.  P u p i l s often thought that the c o n t r o l p l a t e was t o be used as a comparison between the other p e t r i dishes; a technique that could have been l e a r n t from other science s i t u a t i o n s . The p r a c t i c a l d e t a i l s of the experiment made p u p i l s consider using the c o n t r o l p l a t e to check that no b a c t e r i a were seeping i n t o the dishes.  From 58 % of the c l a s s (those  taking part i n c l i n i c a l interviews) only one g i r l and two boys used the c o n t r o l d i s h to substantiate that the agar and p e t r i dishes were s t e r i l e at the beginning of the experiment.  I t was found that p u p i l s ' reasoning to e x p l a i n experiments was  not  simple and that t h e i r p r i o r concepts about b a c t e r i a and those concepts acquired through the course of the experiments appear to influence the p u p i l s ' understanding  of the experimental procedures of s t e r i l i z a t i o n  and  c o n t r o l l i n g v a r i a b l e s . The l o g i c a l demands of the task were problematical to the p u p i l s because the context i n which these demands l a y were providing stumbling blocks f o r understanding  the experiments.  The  suspected interference of concepts i n c o g n i t i v e functions was proposed by Donaldson (1978) and t h i s study supports her view.  Charles' (1976) claim  that the N u f f i e l d Combined Science curriculum can be adopted to be used s u c c e s s f u l l y with nearly the whole a b i l i t y range i n secondary school can be supported i f p r e r e q u i s i t e concepts demanded by the t o p i c and i t s experimental work are i d e n t i f i e d and teachers assess p u p i l s ' p r i o r b e l i e f s to detect any weakness i n these p r e r e q u i s i t e frameworks.  -138-  A n a l y s i s of p u p i l s ' group work revealed i n t e r e s t i n g conclusions about p u p i l a t t i t u d e s t o p r a c t i c a l work. P u p i l s spent l i t t l e time r e f l e c t i n g on the p r a c t i c a l processes of the experiment since t h e i r motivation l a y i n answering questions they thought were provided f o r assessment.  The  researcher gained l i t t l e i n s i g h t i n t o p u p i l reasoning concerning the procedures of the experiment or the concepts p u p i l s possessed from the w r i t t e n answers t o the questions since the p u p i l s were concerned with completing the w r i t t e n work and not r e f l e c t i n g on the q u a l i t y of the task.  I f teachers are i n t e r e s t e d i n a i d i n g p u p i l s ' l e a r n i n g then they need to be aware of p u p i l s ' p r i o r concepts and how they are used i n experiments.  By asking the r i g h t questions teachers can help p u p i l s t o  achieve meaningful l e a r n i n g , but i f they ask the wrong questions - those that do not encourage p u p i l s t o r e f l e c t on t h e i r reasoning - then teachers are p r o v i d i n g p u p i l s with meaningless p r a c t i c a l o p p o r t u n i t i e s f o r concept acquisition.  Providing o p p o r t u n i t i e s f o r concept development would  require a d i f f e r e n t emphasis on assessment and the nature of the tasks i n the classroom.  5.7  I m p l i c a t i o n s of the study This s e c t i o n draws from the d i s c u s s i o n and conclusions of t h i s study  and discusses the i m p l i c a t i o n s of the study on the teaching of laboratory based school science.  Future research that may make p r a c t i c a l lessons a  more useful l e a r n i n g a c t i v i t y f o r p u p i l s i s also discussed.  -139-  5.71  Implications f o r teaching  P u p i l s ' concepts Laboratory  experiments may  be made more useful l e a r n i n g experiences  i f the knowledge provided by these a c t i v i t i e s i s meaningful to the p u p i l . "To acquire knowledge meaningfully  means t h a t the l e a r n e r must incorporate  new knowledge i n t o concepts that the learner already has" (Novak, 1980). This research has shown that p u p i l s with inadequate concepts are u n l i k e l y to possess s u f f i c i e n t s t r u c t u r a l knowledge to incorporate new knowledge, provided by the experiment, i n t o t h e i r framework.  Teachers need t o  i d e n t i f y the concepts embedded i n the experiments being used and then f i n d out the extent to which these concepts are possessed by the p u p i l s p r i o r t o the experiment. P u p i l c o n s t r u c t i o n of concept maps may  be a u s e f u l and  l e s s time consuming method of obtaining t h i s information than using i n t e r v i e w i n g techniques.  However, from interview and mapping methods i t  would be p o s s i b l e to a s c e r t a i n i f the knowledge structures i n long term memory that may  be used to generate meaning from a l e a r n i n g experience  were inadequate or inappropriate.  Tasker (1981) found that p u p i l s '  knowledge s t r u c t u r e s , against which l e a r n i n g experiences were considered, were frequently not those that the teacher assumed the p u p i l possessed. Using concept maps could provide the raw data about p u p i l s ' concepts and t h e i r r e l a t i o n s h i p s t o other concepts and so p o s s i b l y reveal t h i s mismatch between knowledge structures and l e a r n i n g  experiences.  Teaching s t r a t e g i e s I t has been stated (Tasker, 1981)  that p u p i l s tend t o consider each  lesson as an i s o l a t e d event and that they do not associate concepts embedded w i t h i n the task as being l i n k e d with previous l e a r n i n g experiences.  This p u p i l behaviour was e x h i b i t e d by those p u p i l s who  did  -140-  not use t h e i r l i f e concepts of m u l t i c e l l u l a r organisms.  Much of science  p r a c t i c a l work does not encourage the p u p i l t o f i n d l i n k s between knowledge i n long term memory and incoming information.  I f p u p i l s are  asked t o c o n t r o l a l l the inputs o f working memory then they are d e a l i n g w i t h 1) theory t o be r e c a l l e d , 2)  s k i l l s t o be r e c a l l e d ,  3) names of apparatus and m a t e r i a l s t o be recognized and a s s o c i a t e d , 4)  new w r i t t e n i n s t r u c t i o n s ,  5) new s k i l l s , and 6) new verbal i n s t r u c t i o n s . This i s l i k e l y t o lead t o an "overload" s i t u a t i o n which can r e s u l t i n i n e f f e c t i v e l e a r n i n g s t r a t e g i e s characterized by one or more of the f o l l o w i n g p u p i l a c t i o n s : r e c i p e - f o l l o w i n g , copying the a c t i o n s of others, or busy random a c t i v i t y (Johnson and Wham, 1982).  "Overload" can r e s u l t  i n theory a p p l i c a b l e t o the s i t u a t i o n not being used.  The teacher can  help "chunk" incoming information f o r the p u p i l by turning the a t t e n t i o n o f the p u p i l toward the conceptual part o f the information provided by the experiment and the methodological aspects o f the experiment, p r i o r t o the experiment.  Discussion along the l i n e s suggested i n Gowin's (1979)  knowledge "V" organizes the t h i n k i n g side of the V which i s subdivided i n t o events, concepts, p r i n c i p l e s and theory, whereas the doing s i d e of the V deals w i t h objects, records, transformations and knowledge claims. The knowledge claims provide answers t o the question or problem i n focus. The nature of t h i s focus question would depend on the purpose o f the lesson.  P u p i l s have been known t o generate a purpose f o r the l e a r n i n g  a c t i v i t y which i s very d i f f e r e n t from the teacher's intended purpose (Tasker and Osborne, 1983) so i t would be u s e f u l t o e x p l i c i t l y s t a t e the  -141-  purpose f o r the experiment i n advance.  Defining the purpose of the  experiment i n the focus question can lead t o an examination of o b j e c t s and events, theory and concepts so that new knowledge i s constructed (Novak, 1980).  In the present study p u p i l s showed l i t t l e concern about the features of the i n v e s t i g a t i o n considered by the teacher t o be c r i t i c a l design features.  I t may have been h e l p f u l f o r the p u p i l s t o have seen, p r i o r t o  the experiment, the s t e r i l i z a t i o n process of the plates and agar performed, the plates poured and l e f t u n t i l the next lesson.  This would  enable the concept of s t e r i l e t o be discussed i n r e l a t i o n t o other l i f e concepts of b a c t e r i a and a l s o perhaps overcome the problems caused by the loose f i t t i n g l i d s of the p e t r i dishes.  In order to assess that the p u p i l s  1  understanding o f the experiments  i s the same as that of the teacher, a more s e n s i t i v e method o f assessment needs t o be employed other than the normal answering o f questions a t the end o f the task.  I t i s suggested that the concept map provides an  e f f i c i e n t method o f gaining an o v e r a l l p i c t u r e of the extent t o which meaningful l e a r n i n g has taken place and i t also can be used t o suggest f u t u r e i n s t r u c t i o n a l needs. For example, one can l o o k a t the p r o p o s i t i o n s that l i n k concepts as being i n d i c a t o r s of the measure of d i f f e r e n t i a t i o n between constituent concepts.  Nesting o f concepts i s another way o f  demonstrating r e l a t i o n s h i p s between concepts and t h i s can be used as a measure o f integrated r e c o n c i l i a t i o n o f meanings (Cronin e t a l . ,  1982).  Even w i t h l e s s s o p h i s t i c a t e d a n a l y s i s the teacher can a s c e r t a i n the concepts h e l d by the p u p i l and gain i n s i g h t i n t o the p u p i l ' s knowledge  -142-  structure f o r a given content area.  An a l t e r n a t i v e method t o that of w r i t t e n questions f o r assessing p u p i l performance i n the classroom i s d e s i r a b l e since t h i s study has found that p u p i l s are more i n t e n t on completing work t h a t i s obviously assessable rather than r e f l e c t i n g on the o v e r a l l intent of the experiment and t h e i r own i n d i v i d u a l a c t i o n s which they know the teacher i s not able to assess. The p u p i l s ' success or f a i l u r e i n understanding s c i e n t i f i c ideas i s dependent on t h e i r own actions.  P u p i l s need t o be w i l l i n g to  generate meaning f o r concepts and believe that the energy expended on the r e f l e c t i o n of concepts and l i n k i n g them to other b e l i e f s already i n long term memory w i l l a i d them i n the development of an understanding of the ideas of science. Teachers can motivate t h e i r p u p i l s t o do t h i s by encouraging them t o become problem-centred. In order to encourage them t o become problem-centred more emphasis needs t o be placed on the importance of r e f l e c t e d thought rather than the answers t o questions.  For instance,  the answer " b a c t e r i a w i l l grow b e t t e r i n the incubator" ( t y p i c a l answer t o question 7, B a c t e r i a on Ourselves) t e l l s the reader nothing about why  this  occurs or about the concept of growth that the p u p i l possesses. Knowledge, l e a r n i n g and understanding are not l i n e a r .  I t ' s not j u s t a  matter of knowing a l l the items but of knowing how they r e l a t e t o , compare w i t h and f i t i n with each other.  Written t e s t s produced by the teacher,  unless c a r e f u l l y devised, do not t e s t the extent of these r e l a t i o n s h i p s . School work must be such that p u p i l s ' e f f o r t s i n generative l e a r n i n g w i l l lead t o understanding.  f  Learning has been seen t o be influenced by the l e a r n e r ' s perceptions  -143-  and i n t e r p r e t a t i o n s of the events the l e a r n e r encounters.  I t may  be  necessary that w r i t t e n work have focus questions to e x p l i c i t l y s t a t e objectives to c l a r i f y the i n t e n t of a lesson and that i n s t r u c t i o n s encourage the p u p i l s t o consider the important design features of an experiment.  P u p i l s ' achievement can be influenced by the questions  teachers ask p u p i l s or p u p i l s ask themselves.  Group work can help p u p i l s  by encouraging them to r e f l e c t on other perspectives of the task. Learning i n groups i s more l i k e l y to occur when p u p i l s are not placed i n a s i t u a t i o n where assessment of non r e f l e c t i v e w r i t t e n work i s demanded and, instead, p u p i l s are encouraged to produce and present t h e i r own knowledge structures concerning the experiment.  The greatest i m p l i c a t i o n that t h i s study provides f o r teaching i s that of teachers underestimating the power of p r i o r b e l i e f s that p u p i l s bring t o the classroom.  Those p u p i l s with adequate concepts found that  a f t e r experiencing the procedures of the f i r s t experiment they could carry out and i n t e r p r e t the i n t e n t of the second experiment with success.  If  more p u p i l s are to understand experiments then the concepts t h a t are required f o r generating meaning from p r a c t i c a l work need t o be assessed and i f these are found t o be l a c k i n g i n p u p i l s ' frameworks then i n s t r u c t i o n a l sequences ought to be designed t o take account of these a l t e r n a t i v e frameworks.  5.72  I m p l i c a t i o n s f o r research Much u s e f u l research has been undertaken t o uncover p u p i l s '  substantive b e l i e f s concerning many p h y s i c a l science phenomenon.  Less of  t h i s type of research has been involved w i t h concepts i n the b i o l o g i c a l  -144-  s c i e n c e s . The concepts o f l i f e are important i n a l l spheres of b i o l o g i c a l science and y e t do not appear t o have a t t r a c t e d much research a t t e n t i o n . This study has revealed that the p u p i l s ' concepts o f growth and reproduction i n u n i c e l l u l a r organisms can provide u s e f u l stepping stones to generate meaning or hinder comprehension i n the two experiments studied.  I t i s speculated that there are probably d i f f e r e n t b e l i e f s held  concerning growth and reproduction i n simple one-celled organisms than those held i n r e l a t i o n s h i p t o m u l t i c e l l u l a r organisms.  More research i s required i n t o the way meanings are constructed, what motivates p u p i l s t o reorder t h e i r conceptual frameworks and embed them i n t o l o n g term memory. When faced w i t h a problem s o l v i n g s i t u a t i o n p u p i l s may use t h e i r concepts t o construct a s o l u t i o n . p u p i l needs t o understand the problem.  In order t o do t h i s the  Researchers should be asking  themselves what i s the nature of the problem constructed by the p u p i l ? I f a problem i s not constructed then i s t h i s due t o sensory information not cueing aspects of long term memory and how could t h i s cueing procedure possibly work?  This study begins t o look a t the s t r a t e g i e s p u p i l s employ  i n order t o obtain a s o l u t i o n t o problems.  I t also examines how the  p u p i l s ' concepts can i n t e r f e r e with t h i s process.  There are many avenues  of research open i n t h i s f i e l d that may provide useful i n s i g h t i n t o p u p i l s ' mental a c t i v i t y and help teachers devise teaching s t r a t e g i e s accordingly.  I f p r a c t i c a l work i s not t o become an i n t e r l u d e for p u p i l s from other c l a s s work i n science l a b o r a t o r i e s then p u p i l s and teachers must adopt d i f f e r e n t l e a r n i n g and teaching s t r a t e g i e s .  I n v e s t i g a t i o n s i n t o how  -145-  r e f l e c t i v e d i s c u s s i o n may improve the motivation o f p u p i l s t o generate meaning from p r a c t i c a l work could provide key information as t o which teaching s t r a t e g i e s may be more u s e f u l .  Research i n t o p u p i l and teacher  a t t i t u d e s and b e l i e f s about p r a c t i c a l school science has already provided some evidence which may a s s i s t teachers i n r e f l e c t i n g upon t h e i r own teaching s t r a t e g i e s .  This type of research has by no means come t o a  close and i t i s p o s s i b l e t o look forward t o f u r t h e r studies i n v o l v i n g teacher and p u p i l p a r t i c i p a t i o n with teachers becoming researchers i n t h e i r own classrooms.  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Things t h a t you can catch, b a c t e r i a give i t t o you. How do you know about b a c t e r i a , where d i d you f i n d out about b a c t e r i a ? You know the word... Sort of a germ, germs give you d i f f e r e n t diseases. Are a l l these diseases the same? What makes them d i f f e r e n t then? You can pick them up i n d i f f e r e n t ways. D i f f e r e n t germs cause d i f f e r e n t diseases. How could you t e l l a germ from another germ? I don't know. I don't know. Could you look at them and t e l l that they were d i f f e r e n t ? Well you can't r e a l l y see them unless they're under a microscope. So they are very very small? Yea. Are b a c t e r i a germs? Well yea sort of. So what do you include as w e l l as b a c t e r i a as germs? I don't know r e a l l y . So you don't have a d e f i n i t e idea of what germs are? No, not r e a l l y . These b a c t e r i a are they l i v i n g things? Yea. How do you know they are l i v i n g ? They've got to be haven't they. W i l l no - there are l o t s of things t h a t are dead. Well i f they were dead they wouldn't be causing any i l l n e s s e s because you get d i f f e r e n t germs i n s i d e you t h a t k i l l them so you don't get the disease. I s these a b a t t l e raging i n your body between germs? Could be yea i t depends. What does i t depend on? Well I saw t h i s program, I can't remember what disease i t was but they give you an i n j e c t i o n of a c e r t a i n disease, a very mild one. So you catch i t and then your body b u i l d s up s o r t of antigerms t o k i l l them. . Then i f you got the disease again y o u ' l l have the antigerms there ready t o k i l l them. That's good. I t h i n k i t was hooping cough, measles, I can't t e l l you. That doesn't give us a good reason why b a c t e r i a are a l i v e ? They produce don't they? They produce. Yea. They produce what? Other germs. Oh, they reproduce. Yea reproduce that's what I meant. Ok. So you would count that as a major t h i n g of And t h a t ' s what Alive. And what's that s t u f f i n here again...plac  -160-  Int.: C: Int.: C.: Int.: C: Int.: C.: Int.: C: Int.: C.: Int.: C: Int.: C.: Int.: C.: Int.: C.:  Int.: C: Int.: C: Int.: C.: Int.: C.: Int.: C.:  Int.: C.:  Plaque. Plaque - w e l l that produces a c i d doesn't i t . I f they .. when they get anything sweet that produces a c i d . So they are not only reproducing themselves they are producing other t h i n g s . , waste Some do Yea waste tilings Yea Well why do some do t h a t and others don't? I don't know. Ok Well maybe because some get things l i k e germ plaque take i n sugar but the others may not take i n anything. But i f they don't take i n anything would they be a l i v e ? Don't a l l l i v i n g things need food? I don't know. What could these other b a c t e r i a l i v e on i f they don't l i v e on sweet things? Other germs, I t h i n k i n s i d e your body. Would you only f i n d them i n your body - these b a c t e r i a ? Bacteria? Yes. No. Where else would you f i n d them? On your s k i n - I saw another tiling i n a magazine as w e l l that there's about a' thousand of these l i t t l e things i n every square m i l l i m e t r e of your s k i n and i t showed up a piece of s k i n - a t i n y piece of s k i n you could see them a l l over your s k i n . Gosh they must be very small then. Yea. Could they be anywhere e l s e ? I don't know r e a l l y . Where would we pick them up from i f they are on our skin? On our s k i n ? Yea you s a i d there were hundreds and thousands on our s k i n . Well I don't know where we would pick them up. We probably j u s t get them a u t o m a t i c a l l y . W e l l you s a i d we could use other b a c t e r i a t o prevent us from g e t t i n g diseases. Well yes, i t ' s l i k e i n j e c t i o n s . Cause I went t o Holland and I get asthma i f I go near cats because I'm a l l e r g i c t o them. And I went t o H o l l a n d and they had two cats and I had r e a l l y bad asthma. So I had t o go back t o the doctors and he s a i d I had t o go back t o Germany and he give me an i n j e c t i o n before and then I was a l r i g h t then. I see. I t s the same w i t h hooping cough and t h a t - you have i n j e c t i o n s when you're - I saw a program on t h a t - I see a l o t of programs. I t was when I was away l a s t week I was watching t h i s program and i t s a i d you have an i n j e c t i o n when you're s i x months, another when you're one, and another when you're three and then a t f i v e you have a booster and you should be r i d o f hooping cough.  -161-  Int.: C: Int.: C.: Int.: C: Int.: C.: Int.: C: Int.: C: Int.: C.: Int.: C: Int.: C: Int.: C.: Int.:  You should be r i d of i t does ... Well i t doesn't mean that there's no chance of you g e t t i n g but i t s o r t of means that there i s l e s s chance of you g e t t i n g i t . So that means a l l these diseases that we've been t a l k i n g about must be passed on somehow. Yes, breath. I f you breathe or i f you've got a cough and you cough at somebody then t h e y ' l l catch i t . I t can be passed on by touch. Do you have to touch people to get these diseases? No, not r e a l l y , you could touch anything. So the b a c t e r i a are not only on you but on something e l s e . Yes they could be. They are on other t h i n g s . Yes. What happens i f they are not k i l l e d ? They j u s t keep w e l l they go on and on. I'm not sure r e a l l y . Well i n the end they d i e . L i k e chicken pox you can't do anything about them except but whats i t c a l l e d again s o r t of p l a s t e r of p a r i s Oh, Calamine Calamine l o t i o n on them because I had t h a t . They d i e o f f i n the end. I f you s c r a t c h them then they mark and they stay there f o r life. What? The marks, j u s t the marks. Are the marks the b a c t e r i a ? Well I don't know. The b a c t e r i a cause spots. Oh they cause the spots. The s o r t of spotty lumps. Ok. t h a t ' s good.  -162-  APPENDIX A2 Sharon's P r o p o s i t i o n a l Statements B a c t e r i a cause disease B a c t e r i a are l i v i n g L i v i n g because - they form plaque i n teeth - they come back a l l the time - can eat o f f c e l l s B a c t e r i a grow i n f r i d g e B a c t e r i a reproduce B a c t e r i a are found i n food B a c t e r i a are very small B a c t e r i a a r e j e l l y l i k e , transparent B a c t e r i a can be d i f f e r e n t shapes B a c t e r i a may be red or white Plaque on t e e t h i s b a c t e r i a Can h e l p make v a c c i n a t i o n s t o f i g h t disease Concept Map  hi BACTERIA  GROW IN FRIOGE  JElu TRANSPARENT  OIFFERENT SHAPES  COLOURS RSO. UH1TE  LIVING  PLAC UE which REGENERATES  EAT OFF CEU.S  -163-  N e i l ' s P r o p o s i t i o n a l Statements Diseases caused by bad h a b i t s worms, t s e t s e f l y Colds - contagious have t o give them away before i t goes. - caused by water Medicines - work by breaking down c e l l s - a f f e c t bad c e l l s - Bad c e l l s a t t a c k good c e l l s Concept Map  DISEASES  caused by  when MEDICINES  break down  BAO CELLS affect  BAD HABITS  G000 CELLS  eg becomi ng  WET  COLD  causes  COLOS  are  CONTAGIOUS  WORMS  TSETSE FLY  -164-  Mark's P r o p o s i t i o n a l Statements Diseases are caused by d i r t germs Germs caught i n c o l d environments, water Cold caused by germs People spread germs Animals have germs on t h e i r bodies Germs would go i n t o cuts Spread i n body Not b i g enough t o see Look a t them through a microscope Some germs are bigger than others Some germs are more d e t a i l e d Germs l i v e i n animals and the earth Concept Map  -E2.  SOPMd  300IES  -165-  J u s t i n e ' s P r o p o s i t i o n a l Statements Germs cause disease Germs cause colds colds caught i n wet weather Germs cause food poisoning, worms i n food cause disease Germs l i v e i n s i d e people, water, a i r , food D i f f e r e n t types o f diseases caused by d i f f e r e n t types o f germs Medicines k i l l the germs Germs are l i v i n g They are l i v i n g because they cause disease People spread disease by coughing and breathing People develop "immunity" t o disease Concept Map  GERMS  COLOS FOOD HlISOIHMl because cause  PEOPLE OISEASE  COUGHS 3REATHINS  otfretorf TYPES IMMUNITY  -166-  C l i v e ' s P r o p o s i t i o n a l Statements B a c t e r i a g i v e you diseases B a c t e r i a are a s o r t of germ D i f f e r e n t germs cause d i f f e r e n t diseases Can't r e a l l y see them unless they're under a microscope They can be passed on by breathing, touching I f dead wouldn't cause i l l n e s s D i f f e r e n t germs k i l l other germs Antigerms k i l l germs I n j e c t i o n s prevent you g e t t i n g diseases Antigerms b u i l t up i n body They reproduce Plaque produces a c i d Germ plaque takes i n sugar Not a l l germs need food Found a l l over s k i n They are automatically  picked up  Concept Map  BACTERIA  LL  SORT OF GERM  use  LIVING  there are because  MICROSCOPE  DIFFERENT TYPE! found on  e  cause DISEASE  REPRODUCE  SKIN automatical ly picked up BREATHING TOUCHING  produce I ACID  prevented by INJECTIONS killed by ANTIGERMS  and  built up in body "IMMUNITY"  some need  GERM PLAQUE  OTHER GERMS  FOOD  -167-  APPENDIX B Experiment One  : B a c t e r i a i n the A i r  For t h i s experiment you can work i n p a i r s , each member of each p a i r should wash h i s hands before the experiment. You w i l l be provided w i t h p e t r i dishes containing s t e r i l i z e d agar. The dishes have a l s o been s t e r i l i z e d . This means t h a t they are a b s o l u t e l y clean. 1. 2. 3.  4. 5. 6. 7.  Label the plates 1, 2, 3 and 4. Choose a draughty place i n the l a b o r a t o r y , take o f f the l i d and expose the agar of p l a t e 1 to the a i r f o r twenty minutes. Choose a place i n the laboratory where there are no draughts, take o f f the l i d and expose p l a t e 2 to the a i r f o r twenty minutes. You should make a draught screen f o r t h i s p l a t e by surrounding i t w i t h a r i n g of card-board. Expose p l a t e 3 outside f o r twenty minutes. Do not expose p l a t e 4 at a l l . B a c t e r i a grow best at about 37°C, so place the p l a t e s i n an incubator, at t h i s temperature. A f t e r two days remove the p l a t e s from the incubator. I f b a c t e r i a have f a l l e n from the a i r onto the exposed p l a t e s they w i l l grow i n t o c o l o n i e s , and s i n c e the agar i s transparent, there i s no need t o l i f t the l i d o f f the p e t r i d i s h t o see them. Place the whole p l a t e on a piece of black paper and the c o l o n i e s w i l l show up b e a u t i f u l l y .  Experiment Two  : B a c t e r i a on Ourselves  For t h i s experiment you can work i n p a i r s . One member of each p a i r should not wash h i s hands before the experiment. You w i l l be given 3 p e t r i dishes. Label these A, B and C. Each d i s h has been s t e r i l i z e d and contains s t e r i l i z e d agar. 1. 2.  3. 4. 5. 6.  Label the 3 p e t r i dishes A, B and C. P l a t e A The person w i t h washed hands opens A, while t h e i r partner, with unwashed hands very g e n t l y presses the f i n g e r s onto the agar j e l l y so as the not damage the surface. Replace the l i d quickly. P l a t e B The person with washed hands opens the l i d and presses the f i n g e r s of one hand very gently on the medium and then replaces the l i d . P l a t e C Leave unopened. Put the plates i n the incubator at 37°C. A f t e r two days examine the p l a t e s .  -168-  APPENDIX CI C l i n i c a l Interview Two " B a c t e r i a i n the A i r " Steven The interview with Steven began by recapping the experiment. Int: S:  Int: S:. Int: S: Int: S: Int: S: Int: S: Int: S: Int: S: Int: S: Int: S: Int: S: Int: S: Int: S:  What was the point of s t e r i l i z i n g the dishes and the agar before we started? I t h i n k that you s t e r i l i z e the dishes and then the agar because i t would stop any other b a c t e r i a g e t t i n g i n t o the agar or i n t o the dishes. And that b a c t e r i a we don't want. We want the b a c t e r i a from a c e r t a i n place. OK. So are we s t e r i l i z i n g the b a c t e r i a that are already on the glass and i n the agar? Er, what we're doing i s that we're s t e r i l i z i n g the dishes and the agar to get out a l l the other b a c t e r i a that we don't want. OK, and why d i d we clean our hands before? We cleaned our hands before we s t a r t e d so that, so that no b a c t e r i a would get on the glass or the agar which wasn't wanted. So d i d we have b a c t e r i a on our hands then? Yes. And they might get onto the agar. Yes. Why do you t h i n k we decided t o put one i n a draughty room and one i n a non draughty place? I f we have one i n a draughty room i t can t e l l us how much b a c t e r i a i s g e t t i n g i n t o the a i r round there and i n a non draughty place i t can t e l l us how much bacteria i s j u s t f l o a t i n g around. OK f i n e - and why d i d we leave the p l a t e s open f o r so long? Oh, i f we opened them f o r j u s t 2 or 3 seconds the b a c t e r i a wouldn't have much chance to get onto i t so we had to leave them f o r twenty minutes so that b a c t e r i a could s e t t l e onto i t . OK, so we'd have more chance of g e t t i n g more b a c t e r i a then? Yes. Now what was the purpose f o r having p l a t e 4? Now I t h i n k the purpose f o r having p l a t e 4 was so that we could see i f b a c t e r i a seeped i n through the g l a s s , through the gaps or even through the glass onto the agar. Did i t t e l l us anything about the dishes before we s t a r t e d the experiment? What do you mean by that? How do we know whether the dishes were s t e r i l e before we s t a r t e d the experiment? I f you put i t i n the pressure cooker i t i s bound to get r i d of the b a c t e r i a because of the steam and the pressure. How do we know i t ' s bound to? Something might have gone wrong. How would we know i f anything went wrong? I don't know. OK. What kind of explanation can you give f o r these r e s u l t s here? W e l l , on number one i t shows that we have had a l o t of b a c t e r i a .  -169-  Int: S: Int: S: Int: S: Int: S: Int: S:  Int:  This i s the one that's,outside. Yes, and i t ' s a l l b u i l t up i n colonies and they're a l l d i f f e r e n t colours. Do you t h i n k there are d i f f e r e n t types of b a c t e r i a i n there? Yes, I t h i n k that flower-one, i t looks l i k e i t i s d i f f e r e n t t o that yellow smeared one. Yes. OK. Why are some b i g and some small? I t h i n k i t depends on how q u i c k l y they d i v i d e or i t could be the b a c t e r i a i n the a i r and how much there i s o f each. OK. So there are l o t s o f b a c t e r i a i n each of those colonies? Yes. What about the d i f f e r e n c e s between the draughty place, number 3 and number 2, the non draughty place? I t h i n k that i n the non draughty you would get more because o f the, because of the um, w e l l i t i s n ' t draughty so the b a c t e r i a j u s t goes down, but i n a draughty place the b a c t e r i a goes over i t , but i f you put i t outside b a c t e r i a a l s o goes over i t and i t slows down and goes i n . In a draughty place i t ' s always draughty.all the time. OK, that's f i n e .  -170-  APPENDIX C2 C l i n i c a l Interview Three  "Bacteria on Ourselves"  Mark The interview with Mark began by recapping the experiment. Int: M:  Int: M: Int: M: Int: M: Int: M:  Int: M: Int: M:  Int: M:  Int: M: Int: M: Int: M:  What do you t h i n k the r e s u l t s are going t o be? Well, I t h i n k that d i s h A that was the d i r t y hands would have a l o t of b a c t e r i a on i t because I've got a l o t of b a c t e r i a on my hands 'cause I haven't washed them r e c e n t l y . Plate B, the one with clean hands, w i l l have hardly any because he washed h i s hands a few minutes before he put h i s hands i n the j e l l y . So you think the washing w i l l get the b a c t e r i a o f f ? Yes, w e l l some of i t , most of i t w i l l come o f f but some of i t w i l l stay there. So that explains why some w i l l be on the j e l l y . Yes. How about Plate C? P l a t e C I don't t h i n k w i l l have any. Why don't you t h i n k i t w i l l have any? Because i t was closed i n a j a r , i n a plate but some could seep because i f they were f l o a t i n g i n the a i r and i t wasn't c e l l o t a p e d up and i t wasn't sealed i n so I don't think some b a c t e r i a might have been able t o come i n from the a i r , but i t would s p o i l the experiment. Why would i t s p o i l the experiment? Because we are doing i t on ourselves. How could you t e l l i f the b a c t e r i a got i n from the a i r or from ourselves? W e l l , I don't know r e a l l y . There's two d i f f e r e n t kinds o f b a c t e r i a , probably the one i n the a i r you know, you know i s d e t a i l e d . Got l o t s o f you know d i r t y marks and t h a t , but on your hands i t probably hasn't got very much you know because you wash them. I wash them a f t e r breakfast but i f you wash them y o u ' l l s t i l l have b a c t e r i a on them, some are u s e f u l b a c t e r i a . Did i t matter that the p l a t e s were s t e r i l e when we started? Yes, because i f they weren't clean the b a c t e r i a from the a i r and your hands would get i n there before the a c t u a l experiment because we are t r y i n g t o f i n d out that b a c t e r i a are on our hands and not i n the a i r . How could we t e l l i f the b a c t e r i a had got i n before the actual experiment? W e l l , you would probably see the splodges l i k e g r i t i n the d i s h . What was the use of having p l a t e C i f we didn't even open i t ? Well, t o compare the answer, t o compare the d i f f e r e n c e you can see whether C does have more b a c t e r i a or l e s s than the other two. See i f plate C had l e s s than plate B and A or more than plate B and A. You s a i d that you thought there wouldn't be any b a c t e r i a i n there. W e l l , there might be a l i t t l e b i t because i t might you know b a c t e r i a i s f l o a t i n g about how so i t might you know come i n t o plate  -171-  Int: M:  Int: M: Int: M: Int: M: Int:  C. You know come up through the gaps. Would that matter t o the experiment? Well yes, r e a l l y because you're t e s t i n g b a c t e r i a on y o u r s e l f on your hands and i f i t came i n from the a i r then i t ' s not from y o u r s e l f although i f b a c t e r i a ' s f l o a t i n g around now i t might get on your s k i n so r e a l l y b a c t e r i a from the a i r might get onto y o u r s e l f you know i t ' s a guess but i t might do. But i t would be important that those plates were s t e r i l e at the beginning. I t would otherwise i t would s p o i l the experiment because you're not t e s t i n g what's i n the a i r i f you d i d that you're t e s t i n g the b a c t e r i a on your hands OK. Last question. Why do you t h i n k we put them i n a warm place? To keep them at body temperature because you put them i n a warm incubator at 30° a t 37° and that's our body temperature. So the b a c t e r i a would l i k e t o l i v e a t body temperature. Yes. Fine.  -172-  APPENDIX D1 Class Experiment One  " B a c t e r i a i n the A i r " Group A  Mark Martin Robert Steven Robert: Mark: Steven: Robert: Mark: Robert: Mark: Robert: Steven: Mark: Robert: Mark: Steven: Robert: Steven: Mark: Robert: Mark:  Robert: Martin: Robert: Steven: Robert: Mark: Robert: Mark: Steven: Robert: Mark: Robert: Mark: Robert: Mark: Robert: Mark: Robert: Steven: Mark:  (reads) "Choose a draughty place i n the l a b o r a t o r y , take o f f the l i d and expose the ..." Open the window - draughty place. Yes, there i s . I t says put the f i r s t one P l a t e One "Expose i t t o the a i r . " Yes, p l a t e one. "For twenty minutes". Right on your marks get s e t . I ' l l time i t . Look, there's a c l o c k up there. A l r i g h t , what do we do now? Haven't you got something t o put 'round i t ? No. You put both p l a t e s out don't you? No, only one. Look a t the j e l l y . What do we do w i t h the other one? Choose a place i n the laboratory where there are no draughts. "Take o f f the l i d and expose the plate 2 t o the a i r f o r twenty minutes" - but there's no draught. "You could make a draught screen f o r t h i s p l a t e by surrounding i t with a r i n g of cardboard". Use the paper. I ' l l do the card. "Expose p l a t e 3 outside". I've done t h a t , i t ' s outside on the ledge. Right. What's t h i s ? That's the q u e s t i o n sheet, w e ' l l do t h a t a f t e r w a r d , w e ' l l do t h i s first. OK, r i g h t . What about the l a b e l s - we l a b e l them don't we? Do we l a b e l them? We do. I ' l l l a b e l them. P l a t e One i s on the what s h a l l we Put p l a t e One - I ' l l do the w r i t i n g . P l a t e Two. I ' l l do the w r i t i n g up of ideas. OK, you go on then put i t on number one. I t ' s outside. Does i t l i c k on? Yes - Two, Three - we've only got three.  -173-  Steven: Yes. Mark: There, do i t on number two, do i t on the l i d of number two. Martin: What was i n that one? Mark: Er. Martin: What was i n that one? Was that the l i d ? Mark: The j e l l y , i t ' s the j e l l y . Martin: What are we doing? Robert: What we are doing i s t e s t i n g f o r b a c t e r i a and we've got some j e l l y here. Mark: And on the w i n d o w s i l l i n the draught. Robert: We're t e s t i n g the b a c t e r i a i n the a i r . And here we're going to exclude draught from the j e l l y and see, Mark: For twenty minutes. Steven: No, i t doesn't Mark: It is. Martin: How are you going t o t e s t what b a c t e r i a ' s i n that one? Steven: I t ' s going t o take two days. Mark: Well t h i s w i l l t e s t i f there's b a c t e r i a i n the a i r , won't i t ? Robert: Yes. Mark: And t h i s w i l l t e s t t o see i f there's b a c t e r i a j u s t f l o a t i n g about and not i n the draught. What i s number three then? Robert: We've done number three. Mark: What i s number four then? Robert: Expose plate three f o r twenty minutes outside. Steven: I t i s outside. Robert: No, that's the draughty place. Steven: Choose a draughty place i n the l a b o r a t o r y , near the door. Robert: I s i t draughty? Steven: I t must be. Mark: I t said outside though. Steven: No look, I ' l l show you, i t says - look, choose a draughty place i n the l a b o r a t o r y , take o f f the l i d , expose plate one. , Mark: That's plate three outside. Robert: That's plate one. Mark: We'll remember that. Go over i t w i t h a pen, a blue. Steven: That's better. Robert: I ' l l go and change the other one. Steven: Have you put the number on that one? Martin: Why do you have t o go over i t w i t h blue? Mark: Feel l i k e i t . Martin: Why? Mark: Make out a number three. I ' l l put i t outside, r i g h t . Steven: Not outside - i n a draught i t s a i d . ' Mark: Give i t here. Steven: As long as no one comes i n we are a l r i g h t . Robert: Where's the l i d ? Hey you guys, have you taken the l i d o f f p l a t e 4? Mark: Have we got a p l a t e 4? Robert: Because i t says don't take the l i d o f f . Mark: We haven't got one anyway. B a c t e r i a grow - a f t e r two days remove the p l a t e s from the Steven: Incubator - i t ' s got t o go i n an incubator l a t e r . Mark: I f bacteria Robert: We want t o do a l l our ideas now don't we?  -174-  Steven: Robert: Mark: Robert: Mark: Steven: Robert: Martin: Robert: Mark: Steven: Mark: Robert: Martin: Mark: Steven: Mark: Robert: Steven: Mark: Robert: Mark: Steven: Mark: Robert: Steven: Mark: Steven: Robert: Mark: Martin: Mark: Robert: Mark: Martin: Mark: Robert: Mark: Robert: Int: Mark: Int:  Hang on, wait a minute. Number ,one, why do the p e t r i dishes, what's that oh dishes and agar absolutely clean before the experiment began? Because otherwise the b a c t e r i a w i l l be on. I ' l l w r i t e i t . What'd you put then? Answers answers a t the top. Answers and then put i f you didn't wash i t clean i t f i r s t there'd be already b a c t e r i a on i t . I f the agar s o l u t i o n wasn't absolutely clean before the experiment Sterilized, sterilized. Absolutely s t e r i l i z e d . There might be b a c t e r i a . There w i l l be b a c t e r i a , b a c t e r i a ' s everywhere. There would have been b a c t e r i a i n i t already. Yes. On i t . In i t . I t i s i n i t as w e l l . Now what's number two? Why d i d you have to have clean hands at the beginning of the experiment? Otherwise they'd have b a c t e r i a and might spread i t i n . We'd spread the disease i n wouldn't i t . Your hands were cleaned because we would have had bacteria on our hands. Three, three A. Why were dishes opened i n a draughty place. The dishes were opened i n a draughty place The d i s h were opened i n a draughty place (writes) To t e s t i f there i s b a c t e r i a i n the wind In the a i r . To t e s t f o r wind b a c t e r i a because look we had a draught. To t e s t f o r b a c t e r i a i n the wind ( w r i t e s ) . A draughtless place To see To t e s t f o r b a c t e r i a i n calm a i r . To t e s t f o r the presence (writes) For the presence? Yes. For the presence of b a c t e r i a of b a c t e r i a . What d i d you w r i t e f o r B? The dishes were placed i n a draughtless place to t e s t f o r the presence i n a draughtless place. The plates were l e f t open f o r a long time - I t h i n k w e ' l l have to wait f o r the twenty minutes before we can answer t h i s b i t . Yes - I s there a purpose f o r p l a t e four - i f so, what i s i t ? We didn't have p l a t e four but I know why. Look here, do not expose plate four at a l l . Right, I'm j u s t going t o say they're a l l u p s t a i r s . I didn't give them to you because I d i d n ' t want you opening the l i d s . Yes. So you've got 1, 2, 3 and there's a fourth p l a t e s i t t i n g u p s t a i r s whose l i d s have never been taken o f f .  -175-  Steven: Mark: Int: Steven: Robert: Mark: Steven: Robert: Steven: Robert: Martin: Mark: Martin: Robert: Mark: Martin: Steven: Robert: Mark: Robert: 1  Mark: Steven: Martin: Mark: Robert: Mark: Robert: Steven: Robert: Steven: Martin: Robert: Steven: Mark: Martin: Robert: Mark: Robert: Mark: Robert: Mark: Robert: Mark: Robert:  Miss, there's a plate outside. Do we answer t h i s , do we answer question four then? Yes, you can answer that. Was i t because The plates were l e f t open f o r a long time, why was t h i s ? Uh, so that b a c t e r i a could get i n . So b a c t e r i a could get i n . Seep i n t o the container. So that the Have you seen p l a t e 3, i t ' s got a l l b i t s of d i r t i n i t . The plates were l e f t open f o r a long time because so that the b a c t e r i a could seep i n t o the agar. To see i f b a c t e r i a could get i n . Seep i n . Through a closed P l a t e four was unopened t o t e s t i f b a c t e r i a could come throught the g l a s s ? Anything e l s e ? Something about i f being no b a c t e r i a ? does i t change a f t e r being kept f o r a while? B a c t e r i a could seep i n t o the closed container. Yes. I f you could break i n t o the s e a l . Lang's j u s t messing around. I know, and blabbing i n t o t h i s recorder i s important. I f you could break i n t o the sealed container can you imagine what the r e s u l t s w i l l be Yes, those Those exposed t o the most volume. Those exposed t o the most draughty place w i l l have the most b a c t e r i a because i n t h i s room there are more humans. A f a s t draught wouldn't have time t o land on i t . Let's have a l o o k at number three. This i s the worst one exposed t o the most a i r . The one exposed t o the most a i r I s that b a c t e r i a ? The one exposed t o the most a i r Hey look, i s that b a c t e r i a ? Or the draughtiest place Of course i t ' s b a c t e r i a . I wish you'd stop showing o f f i n f r o n t of the tape recorder Steven. I'm not showing o f f . The, the The plates that are exposed t o the a i r The p l a t e s that are exposed t o the most a i r w i l l contain W i l l contain the most b a c t e r i a W i l l contain the most b a c t e r i a . Got two minutes t o go. One minute. S h a l l we turn the tape recorder o f f ? No, leave i t on. You don't mind being turned o f f do you? We'll play i t back when we've done. Stop, b r i n g i t i n . You can have plate one, you p l a t e two, you p l a t e three. Say about your p l a t e i n t o the tape recorder.  -176-  Steven: Mark: Robert: Steven: Robert: Steven: Mark: Robert: Martin: Robert: Mark: Robert: Steven: Robert: Mark: Martin: Robert:  I t says you have t o wait two days i n an incubator. Just say what the r e s u l t s are now. Here are our r e s u l t s now a f t e r exposing our p l a t e s t o c e r t a i n whizzes and a i r . On p l a t e one we have a s w i r l e f f e c t w i t h minute pieces of dust. What was plate one, where was i t ? And p l a t e one was outside our room near a draughty door. P l a t e two was P l a t e two, yeh. P l a t e two was not exposed t o the a i r . But i t was i n i t was... P l a t e two was not exposed t o the a i r , we had We had a r i n g o f paper round i t t o keep out any draught or I t hardly got any b a c t e r i a . There i s a l i t t l e b i t on i t because there wasn't a sealed container over the top but there's not as much as on the others and p l a t e three? P l a t e three seems t o have a l o t of b a c t e r i a on i t because i t was outside on a ledge and has g r a i n s o f d i r t from the wind blowing b a c t e r i a onto i t . Right, i s that i t ? Yes.  -177-  APPENDIX D2 Class Experiment Two  " B a c t e r i a on Ourselves"  Group B  Chris Andrew Michael * * unitelligable vocalizations Andy: Chris: Andy: Chris: Andy: Chris: Michael: Chris: Andy: Michael: Chris: Michael: Chris: Michael: Andy: Chris: Michael: Andy: Chris: Andy: Michael: Andy: Chris: Andy: Chris: Andy: Michael:  Andy: Chris: Michael: Andy: Michael: Chris: Andy: Chris: Andy:  Right, I ' l l l i f t up A and put my d i r t y hands i n . Press them i n , press 'em i n . Ow. You got t o press 'em. * * do you close A? Yes. Right. P l a t e B, the person with washed hands opens the l i d and presses the f i n g e r s of one hand very gently on the medium and then replaces the l i d . Er, f e e l s l i k e slime or something, er f e e l s l i k e snot. E r , smells of something, er smells of d i s i n f e c t a n t . Put that back. P l a t e C leave unopened. Put the plates i n an incubator. Where's an incubator? Not an incubator. Where's the incubator then? I ' l l go and ask her what t o do. Go and ask Miss. Got t o answer the questions now haven't we? Where's the incubator? We haven't got one. We haven't got one - questions. Won't be long. (reads) Questions. "Try and w r i t e down your ideas about the questions on the p l a s t i c overhead projector sheet". Hey (whisper) got t o * * *. Come on. Ask her i f you got t o record t h i s b i t ? Where's the incubator Andy? Don't know - she put them i n there I t h i n k . Try and w r i t e down yor ideas about the questions on the p l a s t i c overhead projector sheet. Your group may be asked t o present t h e i r ideas t o the c l a s s so think out your ideas c a r e f u l l y . I f the person handling the p l a t e s We've got t o be recorded answering the questions. That's what we are doing, we are being recorded. I f the person handling Are we? The p l a t e , what's that? During the experiment d i d not wash t h e i r hands before the experiment would i t make any d i f f e r e n c e t o the r e s u l t ? Yes. Yes. Because  -178-  Michael: Chris: Andy: Michael: Andy: Chris: . Michael: Andy: Michael: Chris: Andy: Chris: Michael: Chris: Andy: Michael: Chris: Andy: Michael: Andy: All: Chris: Michael: Andy: Michael: Andy: Michael: Chris: Andy: Chris: Andy: Michael: Andy: Chris: Andy: Chris: Andy: Chris: Andy: Michael: Andy:  Number one Yes, because then both of them would be the same and you couldn't t e l l the d i f f e r e n c e . And then you couldn't compare a d i r t y hand t o a clean hand. Yes, that's t r u e . The l i v i n g organism Then - then you can compare what? Compare the clean hand w i t h the d i r t y hand. Oh my god, there's a f r o g , a f r o g i n there. Turner come and s i t here, I can't be near that f r o g . Why? To a d i r t y hand. L i f t t h i s and put your hand i n the water. Number two. Where's the frog? I n that j a r . Oh, I've seen that before. Uggh, i t ' s v i l e . It's vile. Number two, why d i d we have p l a t e A unwashed hands? The person with washed hand opens i t up so that when the so that the person Oh, j u s t f a r t e d - s o r r y . Got t o answer t h i s . Why d i d we have a plate A unwashed hands? Because. So we can compare i t with B that i s washed. Write i t down you t i t . (giggles and laughs) Go on, what d i d you say? No, keep i t on. Just 'cause you keep swearing. Right, why d i d we have a p l a t e A unwashed hands? So that we can compare i t with p l a t e B that has unwashed hands r i g h t ? (giggles) Yes. Stop laughing. Stop prancing about l i k e a baby. So we can compare i t w i t h p l a t e B. Why d i d we have a p l a t e B washed hands? So we can compare i t with p l a t e A. So we can compare i t with p l a t e A. Excellent. Hurry up, w r i t e i t down. ( w r i t e s ) Compare i t with p l a t e A. Would you expect t o see a d i f f e r e n c e i n r e s u l t s between the two p l a t e s , why? Yes. Yes, why? Because one w i l l have more b a c t e r i a than the other. Good answer there C h r i s . Glad you thought of i t . Hey look, s t i c k i n s e c t s i n here as w e l l I t ' s l i k e a zoo.  (Diversion w h i l e everyone looks a t s t i c k i n s e c t s ) Andy: Michael: Andy:  Do you t h i n k b a c t e r i a w i l l grow on plate C? No. No, because ...  -179-  Chris: Andy: Chris: Michael: Chris: Andy: Chris: Andy: Chris: Andy: Michael: Chris: Andy: Chris: Andy: Michael: Andy: Chris: Andy: Michael: Chris: Andy: Chris: Andy: Chris: Andy:  No, because i t hasn't been opened. Because i t hasn't been, w e l l i t might have been. Yes, because the b a c t e r i a P l a t e C. I know, because the b a c t e r i a could be out, could get through onto the p l a t e . No, I don't think so. No, that's no good. Just put no. Well I t h i n k i t should. Well you're wrong. Two against one. What's number f i v e ? No, what's number s i x ? Eh? What's question number s i x ? Why do you think we had plate C? We j u s t d i d t h a t . Hold on, we j u s t d i d t h a t . Why do you think we had p l a t e C? E r , t o ... Because we could. To see i f b a c t e r i a could grow i n plates taped up? Yes. Come on question number seven, we are on the l a s t one. Why are the plates placed i n a warm incubator? So that I t can breed. So that the b a c t e r i a can breed and grow. Switch i t o f f , we've stopped.  -180-  APPENDIX E Examples of Work produced from Groupwork Experiment One  : B a c t e r i a i n the A i r  Questions: 1. Why were the p e t r i dishes and agar absoulutely clean before the experiment began? 2. Why d i d you have to have clean hands at the beginning of the experiment? 3. Why were the dishes opened i n a) a draughty place ( p l a t e 1) b) a draughtless place ( p l a t e 2) 4. The p l a t e s were l e f t open f o r a long time, why was t h i s ? 5. I s there a purpose f o r p l a t e 4? I f so, what was i t ? 6. Can you imagine what the r e s u l t s w i l l be? Answers: Example A 1. The dishes had t o a b s o l u t i l y clean before the experiment began so that no germs or b a c t e r i a got i n there. 2. We s t a r t e d the experiment, with clean hands, so that t o prevent g e t t i n g b a c t e r i a on the p l a t e s . 3. a) The dishes were opened i n a draughty place so that they could get b a c t e r i a from which i s c a r r i e d i n the wind, b) The dishes were opened i n draughtless place so that they could get b a c t e r i a from the a i r i n a room. 4. Yes we do t h i n k t h a t there i s a reason f o r p l a t e 4 so that you can see the d i f f e r e n c e between the exposed and the non exposed. 5. We imagine that the r e s u l t s w i l l be a l l d i f f e r e n t because of the d i f f e r e n t place that they were i n . Example B 1. So that no germs could create on the dishes and they would be sterile. 2. We had t o have clean hands because we didn't want t o get germs or d i r t i n s i d e our p e t r i dishes. 3. a) The d i s h was opened i n a draughty place because the a i r had to get t o i t . b) The d i s h was opened i n a draughtless place so a i r can only get i n from the top. 4. The p l a t e s we exposed f o r a long time were l i k e t h i s because the germs had t o get i n t o the p l a t e . 5. Yes there i s a purpose f o r p l a t e 4. No b a c t e r i a can get t o i t . 6. We t h i n k the p l a t e outside w i l l have a l o t of germs on i t . The one i n the card w i l l have q u i t e a l o t of germs on i t , and the ones which were covered the whole time had no germs on them.  -181-  Example C 1. I f the p e t r i dishes and agar s o l u t i o n wasn't absolutely clean when the experiment began there would have been b a c t e r i a i n i t already. 2. Clean hands were needed because we would have had bacteria on our hands. 3. a) The dishes were opened i n a draughty places t o look f o r b a c t e r i a i n the wind, b) The dishes were opened i n a draughtless place t o look f o r the presence of b a c t e r i a i n a draughtless place. 4. The p l a t e s were l e f t open f o r a long time so that b a c t e r i a could seap i n t o the agar. 5. Plate 4 was unopened t o t e s t i f b a c t e r i a could seap i n t o the sealed container. 6. The p l a t e s exposed t o the most a i r w i l l contain the most b a c t e r i a . Experiment Two : B a c t e r i a on Ourselves Questions: Try and w r i t e down your ideas about the questions on the p l a s t i c overhead projector sheet. Your group may be asked t o present t h e i r ideas t o the c l a s s so t h i n k out your ideas c a r e f u l l y . 1. I f the person handling the plates during the experiment d i d not wash t h e i r hands before the experiment would i t make any d i f f e r e n c e t o the r e s u l t ? 2. Why d i d we have p l a t e A? (unwashed hands) 3. Why d i d we have plate B? (washed hands) 4. Would you expect t o see a d i f f e r e n c e i n r e s u l t s between the two plates? Why? 5. Do you t h i n k b a c t e r i a w i l l grow on plate C? 6. Why do you t h i n k we had p l a t e C? 7. Why are the plates placed i n a warm incubator? Answers: Example D 1. Yes the plates would be d i f f e r e n t because we would c o l l e c t germs that we d i d not want. 2. We had p l a t e A so we could see the d i f f e r e n c e between plate A and p l a t e B. 3. We had p l a t e B so we could see the d i f f e r e n c e between plate B and p l a t e A. 4. Yes we would expect t o see a difference between the two p l a t e s because on plate A we would expect t o see germs and on plate B we would expect not t o see any germs. 5. No, we wouldn't expect t o see germs on p l a t e C because i t has not been opened unless germs can get through t o i t . 6. We had p l a t e C t o see i f the germs could get i n t o the agar and t o  -182-  see the d i f f e r e n c e . 7. The p l a t e s were put i n a warm incubator so that the germs could grow i f any. Example E 1. I f the person that washed t h e i r hands didn't wash t h e i r hands plate A and B would be the same because p l a t e A the person who didn't wash there hands put the f i n g e r s i n the j e l l y and p l a t e B the person who d i d wash t h e i r hands put t h e i r f i n g e r s i n the jelly. 2. We had p l a t e A f o r unwashed hands so that we could see how much b a c t e r i a was on your hands. 3. We had p l a t e B so that we could compare t o see i f the b a c t e r i a was s t i l l there a f t e r washing your hands. 4. Yes we would expect t o see a d i f f e r e n c e because the unwashed hands had more b a c t e r i a on them and with plate B most of the b a c t e r i a was washed away. 5. We think that very l i t t l e b a c t e r i a w i l l get i n t o plate C because i t hasn't been opened the only way i t could get through i s by a gap i n the j a r . 6. We had p l a t e C j u s t t o see i f i t was possible f o r b a c t e r i a t o get in. 7. The p l a t e s were placed i n a warm incubator so that the b a c t e r i a would grow a t the same rate as on our hands. Example F 1. Yes, i f the person handling the plates during the experiments d i d not wash t h e i r hands before the experiment when he opened the l i d b a c t e r i a would get i n from the hands. 2. We had p l a t e A (unwashed hands) t o compare with plate B (washed hands). 3. We had p l a t e B (washed hands) t o compare the d i f f e r e n c e w i t h p l a t e A (unwashed hands). 4. You would expect t o see a d i f f e r e n c e i n r e s u l t s between the two plates because unwashed hands would have a l o t of b a c t e r i a but washed hands would have very l i t t l e . 5. No, b a c t e r i a w i l l not grow on plate C. 6. We had p l a t e C t o see i f b a c t e r i a could seap i n t o the p l a t e . 7. The p l a t e s were placed i n a warm incubator t o keep them at our body temperature.  -183-  APPENDIX F Examples o f work produced from Homework Experiment One : B a c t e r i a i n the a i r Questions: 1. Why were the p e t r i dishes and agar absolutely clean before the experiment began? 2. Why d i d you have t o have clean hands a t the beginning o f the experiment? 3. Why were the dishes opened i n a) a draughty place ( p l a t e 1) b) a draughtless place ( p l a t e 2) 4. The p l a t e s were l e f t open f o r a long time, why was t h i s ? 5. I s there a purpose f o r p l a t e 4? I f so, what was i t ? 6. Can you imagine what the r e s u l t s w i l l be? Answers: Nicole 1. The p e t r i dishes and agar had t o be absolutely clean before the experiment began because otherwise i f any other b a c t e r i a got on i t that we didn't want we wouldn't get the r e s u l t s we wanted. 2. We had clean hands before the experiment because i f you didn't b a c t e r i a from your hands would get onto the dishes. 3. a) P l a t e 1 was opened i n a draughty place because then we could see what b a c t e r i a gets c a r r i e d i n the wind, b) P l a t e 2 was opened i n a draughtless place because we could see what b a c t e r i a was i n the a i r around us. 4. The p l a t e s were l e f t open f o r a long time because we had t o make sure a l o t of b a c t e r i a got on the p l a t e s . 5. There i s a purpose f o r p l a t e 4 i t i s - : p l a t e 4 was l e f t unopened because you can see the d i f f e r e n c e between p l a t e s 1, 2 and 3 against p l a t e 4. 6. I imagined that the p l a t e s except p l a t e 4 would have small blobs on them and they would a l l kind of l i n e s over them. Mark 1. The p e t r i dishes agar were absolutely clean before the experiment because b a c t e r i a would be on the dishes already and would s p o i l the experiment. 2. We had t o clean our hands, because b a c t e r i a would be on them and the agar would get b a c t e r i a on i t when we touched i t . 3. a) The d i s h was opened i n a draughty place t o see what the b a c t e r i a i s l i k e i n the wind, b) The d i s h was opened i n a draughtless place t o see what the b a c t e r i a i s ' l i k e i n a place with no draughts.  -184-  4. The p l a t e s were l e f t open f o r a long time because then b a c t e r i a would have a chance of s e t t l i n g i n the agar. 5. There i s a purpose f o r p l a t e 4. You can compare the 3 p l a t e s exposed t o a i r and p l a t e 4 which was not exposed t o a i r . 6. You can imagine what the r e s u l t s w i l l be. The dishes exposed t o the most a i r w i l l have more b a c t e r i a than the dishes exposed t o not much a i r . Robert 1. The p e t r i dishes and agar were absolutely clean before the experiment began because b a c t e r i a would be on them and they would show up i n the agar. These b a c t e r i a would be the wrong b a c t e r i a , as we were searching f o r b a c t e r i a i n the a i r . 2. You have to have clean hands at the beginning of the experiment because the d i r t and b a c t e r i a on them would show up on the p e t r i dishes, so s p o i l i n g the experiment. 3. a) The dishes were opened i n a draughty place t o t e s t f o r b a c t e r i a i n a draught, to see whether they accumulate i n a breeze or i n s t i l l a i r . b) And the dishes were opened i n a draughtless place to t e s t f o r b a c t e r i a i n s t i l l a i r , and so that i t could be compared w i t h dishes placed i n draughty places. 4. The p l a t e s were l e f t open f o r a long time so as t o l e t the bacteria settle. 5. There was a purpose f o r p l a t e 4. This was t o see i f b a c t e r i a could seap i n t o the sealed j a r , and so that i t could be compared w i t h the opened dishes. This would show the presence of b a c t e r i a i n the a i r . 6. The r e s u l t s w i l l be that those dishes exposed t o more a i r w i l l have the most b a c t e r i a on the agar. We got the r e s u l t s we drew because the dishes exposed t o the most a i r had more b a c t e r i a on them, because more b a c t e r i a passed over and on them. Experiment Two : B a c t e r i a on Ourselves Questions: 1. 2. 3. 4. 5.  What are the r e s u l t s f o r p l a t e s A and B? Why do you t h i n k you got these r e s u l t s ? Have any bacteria grown on plate C? Give a reason f o r your answer. Are there d i f f e r e n t types of b a c t e r i a growing on p l a t e s A and B? Explain your answer. 6. What things could a f f e c t the growth of b a c t e r i a i n the dishes? 7. Did i t matter i f the p l a t e s were s t e r i l e before the experiment began? 8. How could you prove that they were e i t h e r s t e r i l e or not s t e r i l e ?  -185-  Answers: Nicole 1. The r e s u l t s f o r p l a t e A and B were b a c t e r i a had grown i n s i d e the agar. They were small dots. 2. We got these r e s u l t s because they had germs and b a c t e r i a on them. 3. There shouldn't be b a c t e r i a on plate C. 4. No a i r has got i n t o p l a t e C because we never opened i t . 5. There are d i f f e r e n t types o f b a c t e r i a because one person washed there hands and one person didn't. 6. Heat could a f f e c t the growth of b a c t e r i a . 7. I t d i d matter i f the p l a t e s were s t e r i l e . 8. You could prove they were s t e r i l e because they had j e l l y i n them. Mark 1. The r e s u l t s from p l a t e A and B are that B (washed hands) has l e s s b a c t e r i a than p l a t e A (unwashed hands) though there i s not that much d i f f e r e n c e . 2. I t h i n k I got these r e s u l t s because d i r t y hands have more b a c t e r i a on them than clean hands. 3. No b a c t e r i a has grown on p l a t e C. 4. The reason f o r t h i s i s because we kept the p l a t e sealed, and so no b a c t e r i a could get i n . 5. Yes there are d i f f e r e n t types o f b a c t e r i a growing on plates A and B, A has got "splodges" and b i g c e l l s and are on t h e i r own but B has got l o t s o f l i t t l e ones stuck together. 6. A i r could a f f e c t the growth of b a c t e r i a i n the dishes. 7. Yes, i t d i d matter i f the plates were s t e r i l e before the experiment began. 8. You could prove that the dishes were s t e r i l e or not because plate C was s t e r i l e and so were B and A, C was clean. Robert 1. The r e s u l t s f o r p l a t e s A and B are that B, washed hands, had l e s s b a c t e r i a than A, unwashed hands, though there i s not that much difference. 2. I t h i n k we got these r e s u l t s because d i r t y hands have more b a c t e r i a on them, than washed hands have. 3. No b a c t e r i a have grown on p l a t e C. 4. The reason f o r my answer i s that the p l a t e was sealed, so no b a c t e r i a could get i n . 5. Yes, there are d i f f e r e n t types o f b a c t e r i a growing on p l a t e s A and B, because there are d i f f e r e n t types of b a c t e r i a on d i r t y hands, than there are on clean hands. 6. The things that c o u l d - a f f e c t the growth of b a c t e r i a i n the dishes are the a i r , i f there was none, so the b a c t e r i a couldn't breath. This would happen i f the l i d was sealed. I f food, such as agar, wasn't present then the growth of the b a c t e r i a would be a f f e c t e d .  -186-  7. I t d i d matter i f the plates were s t e r i l e before the experiment, because unwanted b a c t e r i a would be on the dishes, so s p o i l i n g the experiment. 8. You could prove that they were s t e r i l e or not by adding some agar s o l u t i o n . Any b a c t e r i a present would grow and would be a b l e t o be seen. I f none grew then the d i s h would be s t e r i l e .  

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