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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 t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g - o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department o r by h i s o r her r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department o f tomHOAATics Pr*i_. Sopice. eot*-cKuod The U n i v e r s i t y o f B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date t*\ DE-6 (3/81) 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 is 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 el 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 i i i -experiment. Pupils' concepts of the growth of bacteria were found to be varied. 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. - i v -TABLE OF CONTENTS Abstract i i L i s t of Tables i x L i s t of Figures x Acknowledgements x i Chapter One 1.1 Introduction 1 1.2 Background to the problem 2 1.3 Statement of the problem 4 1.31 General problem area 4 1.32 S p e c i f i c research questions 6 1.4 Some general methodological issues 7 Chapter Two 2.0 Psychological context 9 2.1 Cognitive issues versus conceptual issues 9 2.11 Piaget's work as used by Shayer 10 2.12 A l t e r n a t i v e perspectives 15 2.2 Concept Learning 21 2.21 P u p i l s 1 concepts of bacteria p r i o r to i n s t r u c t i o n 25 2.211 P u p i l s ' concepts of l i v i n g things 25 2.212 Pupi l s ' c l a s s i f i c a t i o n of l i v i n g things 26 2.22 Pupils' a b i l i t y to i s o l a t e and control variables 28 2.23 The demands of pu p i l s ' work i n the science classroom 34 2.3 Educational implications 41 2.31 I n s t r u c t i o n a l s t r a t e g i e s 43 2.32 Laboratory work 44 -V-2.33 Problem solving 45 Chapter Three 3.0 Methods of study 48 3.1 Introduction 48 3.11 Background to methods used in the study 51 3.12 The clinical interview 53 3.13 Classroom data 55 3.2 Methods of data collection 57 3.21 Data collection schedule 57 3.3 Description of the clinical 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 Pupils' sources of information 74 4.2 Pupils' beliefs elicited from Clinical Interview Two 78 4.21 Pupils' identification of bacteria 7 8 4.22 Bacteria as living units 79 Pupil significance of sterile equipment and medium 79 Pupil significance of the control plate in the experiment 84 4.23 Pupils' overall understanding of the experimental procedures 85 - v i -4.3 Pupils' 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 results 89 4.32 Pupils' views on the significance of the s t e r i l e equipment and medium 90 4.33 Pupils' views on the significance of the control plate i n the experiment 92 4.34 Pupils' o v e r a l l understanding of the experimental procedures 93 4.4 Pupils' 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" 101 4.5 Results of group work (written answers) 103 Chapter Five 5.0 Introduction 108 5.1 Discussion of pupils' b e l i e f s about bacteria 109 5.2 Discussion of pupils' interaction of the experiments i n the study 113 5.21 Analysis of concepts required to understand the experiments 115 5.22 Pupils' prior b e l i e f s 117 5.221 I d e n t i f i c a t i o n of bacteria 117 5.222 The concept of colony 118 5.223 Pupils' concepts of s t e r i l i z a t i o n 119 5.224 Pupils' perceptions of the role of the control plate 122 5.3 Pupil held concepts affecting the understanding of the experiments 123 - v i i -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 159 A2 Examples of concept maps produced from transcripts of Clinical Interview One 162 B Description of experiments 167 Experiment one "Bacteria in the Air" Experiment two "Bacteria on Ourselves" C1 Example of a transcript produced from Clinical Interview Two 168 C2 Example of a transcript produced from Clinical Interview Three 170 D1 Example of a transcript produced from audio-taped group work of experiment one "Bacteria in the Air" 172 D2 Example of a transcript produced from audio-taped group work of experiment two "Bacteria on Ourselves" 177 - v i i i -E Examples of work produced from group work 180 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 " F Examples of work produced from homework 183 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 -ix-LIST OF TABLES Table I Summary of data gathering schedule for Experiment One 5 8 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 for the following study i s found i n the N u f f i e l d Combined Science curriculum project, an English science scheme that followed from the implementation of Nuffield '0' l e v e l science courses. The Combined Science team, set up i n 1966, had the task of synthesizing these materials to provide work suitable for children 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 extensively 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 to i t s alleged mismatch with the average pupils' cognitive operational l e v e l (Shayer, 1978). This study has been carried out i n an English Secondary School with average a b i l i t y second year pupils and focuses on children's b e l i e f s about bacteria. I t i s believed that the context of the experiments used should be interpreted more i n terms of the pupil's understanding of bacteria 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 carried out i n a school in England, the selection of the concept area, the problem i n which the concept i s embedded and the issues surrounding the role of the pupil's cognitive operational l e v e l in school performance are a l l applicable to current curriculum issues i n science education a l l over the world (Wollman, 1978). -2-1.2 Background to the problem Science c u r r i c u l a for average B r i t i s h secondary school pupils have often been based on other s y l l a b i intended for the c h i l d of above average a b i l i t y . Of the curriculum used i n teaching average a b i l i t y pupils * Nuffield Combined Science subject matter draws heavily on the materials developed by the separate Nuffield '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 for the average secondary school pupil (Shayer, 1974). The r e s u l t i s that t e s t s , l i k e Nuffield Combined Science, include experimental work which, according to Shayer fs (1974) analysis require the pupil to have reached the Piagetian stage of formal operational thought i n order to understand some of the sophisticated ideas presented. Shayer has argued, based on an analysis of the Nuffield '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 old pupil with an intelligence quotient of at least 125 would be able to cope with the l e v e l of thinking presented i n these materials. The rest of the school population, he suggests, would gradually acquire the required formal operational s k i l l s at l a t e r ages. This would mean that most pupils would have spent two or more years attempting to cope with problems and experiments which required formal operational thinking when i n fact they were only capable of using concrete operational strategies to understand the p r i n c i p l e s and concepts found i n these materials. I t would appear that some "borrowed" Nuffield '0' l e v e l concepts would be equally unsuitable for the lower a b i l i t y class as they appear i n the Nuffield Combined Science scheme. - 3 -In contrast to Shayer's position, outlined above, Charles (1976) 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 is suitable and useful for approximately the upper 7 5 percent of the ability range. Below that i t becomes increasingly difficult 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 (1976) who found the majority of teachers believed that many sections were suitable for second year (13 year old) pupils. Views held by Charles ( 1 9 7 6 ) , Carter ( 1 9 7 6 ) , and Shayer (1974) 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 will 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 is set. It is to this issue of the role of context that other researchers have addressed their interest (Driver and Erickson, 1 9 8 3 ; 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 "critical barriers" (Hawkins, 1978) thereby limiting their understanding -4-of the disciplinary concepts presented by the curriculum. Research is 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 will 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 is 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 in 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 is presented. It is 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 is believed the students will 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 is 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 is unaquainted with the concepts held by the pupil, or how they were obtained. In turn, the student is 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 will often modify the curriculum to suit the ability of the pupil without being aware of the alternative frameworks belonging to the pupil. It is hypothesized in the present study that these frameworks have more importance in understanding the nature of the difficulties 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 will 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 first year of secondary school. During this period of time they would also have had limited experience in laboratory practical work involving controlling variables. It is thought that the substantive beliefs elicited by the interview technique of the first clinical 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 is 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 is 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 difficulties occur will 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 increasingly obvious interest i n Piagetian developmental psychology and i t s curriculum development. Piaget's stage theory produced the hope that ins t r u c t i o n would become more successful i f learning tasks matched the cognitive stages already reached i n the pupils' psychological development. Other researchers interested i n pedagogy but not agreeing with Piaget's emphasis on the stages of cognitive development have sought alternative theories for 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 for research and have claimed that i t i s i l l - s u i t e d to finding ways of improving instruction since the veracity 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 for descriptive convenience only (Toulmin, 1971). L i t t l e i s known concerning the rules of t r a n s i t i o n from one stage to another despite Piaget's mechanisms of stage t r a n s i t i o n . Discrepant evidence supporting the idea that Piaget's operational structures 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 topic for debate. With the development of the Nuffield 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 practice i n science teaching, developed by adaptation to the top 15-20 percent of the school population, a satisfactory model for the other 80 percent of pupils? Was i t possible to keep our existing models of science education while modifying them suitably for the less able pupil?" (Shayer, 1979). Piagetians maintain that learning takes place most e f f e c t i v e l y when the child's present conceptual l e v e l (cognitive structure) i s matched closely with the operational demands of the subject matter. Shayer (1974) assessed the section being studied i n t h i s thesis, bacteria and disease, as requiring a 3A minimal conceptual age and that the tasks being demanded of the c h i l d were at least one year ahead of the cognitive development of selective pupils (top 15-20 percent of school population). This suggests that pupils not attaining 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 interest has been shown i n the match of science c u r r i c u l a to the learner i n the middle and secondary school. This match i s said to have been achieved through an operational analysis 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 for analysing the curriculum and assessing the l e v e l of thinking of the pupil population. Both the analysis and assessment have been c r i t i c i z e d with respect to experimental design and Shayer's heavy reliance on a Piagetian framework (Driver, 1979; Wollman, 1978). This framework was used as i t was thought possible to analyse both the demands of the curriculum and provide a method of -11-estimating the cognitive l e v e l of the p u p i l . The underlying model of CSMS work assumes Piagetian tests do test cognitive development. Shayer (1981) rejects the alternative interpretation that the Piagetian tests measure the pupils' grasp of concepts they have learned and not cognitive development. A taxonomical method was implemented for analyzing the Piagetian l e v e l of thinking demanded by a Science Curriculum (Shayer, 1972). This was achieved by assessing the l e v e l of operational development possessed by the c h i l d i n Piagetian terms then predicting the supposed Piagetian l e v e l of thinking demanded by an examination of the content objectives and exam items of the course. The exam items were c l a s s i f i e d beforehand for supposed Piagetian cognitive stage development required for the i r comprehension. Only pupils at the 3A stage of formal thought were considered to have an opportunity to succeed on tasks designated as being 3B i n cognitive demand. Cr i t i c i s m has been leveled at t h i s analysis (Driver, 1979) since the l o g i c a l demands of the task may not be problematical to the pupil but the context i n which these demands l i e , due perhaps to the pedagogical approach adopted, may cause the pupil to be unable to cope with the cognitive task. Other researchers have suggested that memory demands may af 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 to a greater extent than acknowledged by Piaget (Wollman, 1978). One of Wollman's c r i t i c i s m s of placing tasks i n l e v e l s of cognitive demand i s that i n a s t a t i s t i c a l sense, the within group variance of the tasks i s too great to be useful. -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 difficulty 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 is 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 is 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 is 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 is unable to predict performance and performance is 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 is quite confusing and i t is difficult to understand the exact -14-meaning of the term. There is 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 is 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 is as important as the task itself when attempting to classify a task as eliciting formal operational thought from a pupil. Munby's (1980) criticism is that the research community is running the risk of being careless i f the notion of being at a stage is used. The ambiguities in research reports abound as to who will have reached formal operational thought by a certain age and what forms of reasoning constitute this stage. Munby reports that the temptation is to "take things quite lite 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 will tolerate without abandoning the stage concept, is an -15-interesting one" (p. 11 ) . 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 is effected by basing the teaching-learning process on theory. Piaget's educational contribution is 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 child's thinking 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 investigating topics 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 structure but more on how information i s processed. Ausubel (1963, 1968) does not view his theory i n opposition to Piaget's. The key issue i s "whether children develop general 'cognitive structures' or 'cognitive operations' to 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 concepts, each of which or some combination permits them to make sense out of experience" (Novak, 1977b, p. 455). Novak believes that children 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. Similarly for Bruner (1965) the structure of the topic l i e s i n the d i s c i p l i n e considered; how things are related within a particular d i s c i p l i n e . Piaget's concept of structure d i f f e r s from Bruner's since Piaget develops the idea of the c h i l d actively structuring his 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 action, which modifies the object of knowledge..." (Piaget, 1964, p. 8). For Piaget the concept of structure i s a property of the child's mind. Duckworth (1964) contrasts Bruner with Piaget on the idea of structure i n the curriculum: "The question comes up whether to teach the structure or to present the c h i l d with situations where he i s active and creates the structures 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 to 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 will 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. Unfortunately teachers often do not know the child's viewpoint. Bruner's method of teaching is to induce understanding by tying down isolated segments of knowledge. The development of basic transformations of cognitive structure is 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 is 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, is optimistic concerning the role of language as a coordinator and integrator of experience. Likewise -18-Ausubel's perspective is 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 fitting new units of information into a category of preconceptions already held by the learner. New learning is 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" is related to a large array of information the pupil already possesses (Novak, 1976) i t is 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 into his own system. 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 is the relationship of the new item and its 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-to t h i s , the teacher should possess some insight into the knowledge possessed by the t y p i c a l p u p i l . Discovery of the child's point of view i s also a recommendation made by Margaret Donaldson (1978). She c i t e s research which claims that children 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 pupil shows less egocentrism and i n a b i l i t y to decentre. Piaget considers that the growth of the a b i l i t y to decentre i s c r u c i a l since the making of 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 to doubt whether the child'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 acquisition 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 learning a c t i v i t y . This makes great demands on the teacher's capacity to decentre since "an adult's knowledge of the general nature of the subjects taught to children when they f i r s t enter school i s apt to be so wel l established that i t blocks the r e a l i z a t i o n of precisely what the children need to be helped to 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 significance of s c i e n t i f i c procedures may not be relevant to the pupil i n the science laboratory. Teachers need to gain insight into what pupils consider relevant i n order to make science more meaningful. Making school science meaningful has been the purpose of the two dominant viewpoints that have influenced research on learning 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 is 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 is 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. He calls this meaningful problem solving. 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 is considerable evidence from recent research of the important role played by the ideas that children bring with them to school. It is 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 in order that the lesson be effective in terms of the teacher's aims and objectives. The aim of every teacher is to promote the pupils' acquisition of correct scientific concepts. When a concept has been meaningfully learnt or acquired the student can define its critical attributes and consequently recognize new, unfamiliar instances of the particular concept (Bruner et al., 1956; Ausubel, 1968; Klausmeier et al., 1974; Herron et al. , 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 is 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 its class examples of the concepts is 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 in 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 correctly to i t s class examples of the concept, e.g. to classify l i v i n g or non l i v i n g things. Level 4 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 classify 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 well be a requirement for the individual's conceptual framework to undergo change in order that the biological 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 existing beliefs acting as 'stumbing blocks' (West, 1982) and would seem a drastic conceptual process. In contrast, the evolutionary change tidies up the student's beliefs and these may even provide the 'building blocks' (West, 1982) for change. The "small scale" change or "assimilation" that Strike and Posner (1982) suggest may be prompted when teachers attempt to link old and new knowledge. -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 for comparison against pupils' concept maps caused by MICROSCOPIC PATHOGENIC because HARr Fill 8ACTERIA are LIV INS NITROGEN CYCLE used in PLANT/ANIMAL MATERIAL break-down USEF UL MOVE by AIR WATER GROWTH GJ KM 1 * INCRE IN CYTOP -ASE 1ASH REPRODUCE RESP IRE by I producM SENS I TIVE l t d ANTIBI OTICS DISEASE CONSUME S art SAPROPHY IC break down PRODUCERS are AUTOTROPHIC build up F000 MATERIAL -25-2.21 Pup i l s ' concepts of bacteria p r i o r to i n s t r u c t i o n I t i s possible to examine the many concepts associated with the term bacteria by generating a concept map. The concept map represents one person's understanding of that term. Figure 1 i l l u s t r a t e s a concept map produced by the author. The terms i n the boxes are concepts and these are connected by propositions to other concepts. A comparison o f a t y p i c a l map drawn by a pupil with that of one drawn by the teacher may a s s i s t the teacher to understand better some of the d i f f i c u l t i e s experienced by pupils i n i n t e r p r e t i n g a given i n s t r u c t i o n problem. For example, to understand the r o l e of bacteria i n the experiments the pupil must have some understanding of the concept of " l i v i n g things" and s i z e of " b a c t e r i a l organisms". 2.211 Pup i l s ' concepts of l i v i n g things Although there has never been a si n g l e d e f i n i t i o n of the concept of l i f e that would be s a t i s f a c t o r y to many b i o l o g i s t s , seven c h a r a c t e r i s t i c s of l i v i n g organisms used i n school are 1) growth, 2) reproduction, 3) r e s p i r a t i o n , 4) n u t r i t i o n , 5) excretion, 6) i r r i t a b i l i t y , and 7) locomotion. These seven c h a r a c t e r i s t i c s better i l l u s t r a t e the animal kingdom at 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 bacteria 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 not obvious that they comply with any of the above c h a r a c t e r i s t i c s since they are so small. Piaget (1929) i d e n t i f i e d four stages which characterize the development of the " l i f e concept" i n ch i l d r e n . The f i n a l stage achieved by eleven year old children and upwards showed the a b i l i t y to c o r r e c t l y i d e n t i f y only l i v i n g creatures as being a l i v e and possessing -26-consciousness. L i f e has many meanings as f a r as children are concerned. From a study of 83 students, grades 5-9, 45 percent understood the continuity of l i f e (Tamir et a l . , 1981). Thirty-six percent realized that l i v i n g organisms originate from other l i v i n g organisms, but were not able to explain t h i s r e l a t i o n s h i p . Nineteen percent believed that " i t i s possible for l i v i n g organisms to develop from nonliving". Ninety-nine percent of children 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 pupils interviewed could use the words ' l i v i n g things' appropriately. They found that the performances of pupils 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 pupils. F i f t y percent of the fourth year (15 year olds) biology pupils were s t i l l unable to correctly 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 distinguishing between 'alive and dead* and 'dead and non l i v i n g ' i n set tasks (Brumby, 1982). Even children who correctly 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 to associated b i o l o g i c a l attributes (such as) n u t r i t i o n ... respiration ... reproduction" (Looft, 1974, p. 289). 2.212 Pupils' c l a s s i f i c a t i o n of l i v i n g things Researchers have also examined pupils' a b i l i t y to 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 easier to c l a s s i f y animals as l i v i n g organisms than plants. 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 cognitive process. I t i s 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 that there are two kinds of 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 rely on verbal d e f i n i t i o n e.g. the difference 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 classes. With a few exceptions they did not possess r e l i a b l e class concepts. This was revealed by th 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 thirty-nine ten to f i f t e e n year olds revealed that a l l but s i x used the number of legs to categorize instances and non instances of the concept of "animal". The common meaning of the word "animal" appeared to refer 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 pupils at l e a s t once. Results showed that the smaller the organism the l e s s l i k e l y i t would be animal. A few pupils used the c r i t e r i o n of movement as an attribute of l i v i n g things ( B e l l , 1981). - 2 8 -Simpson and Arnold ( 1 9 8 2 ) and others have shown that pupils who have experienced two years of secondary school science do not posses a precise concept of living 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 is unlikely to be useful to commence teaching about bacteria in the second year when "living" is 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 . 2 2 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, 1 9 8 4 ) . 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 critically 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 child's a b i l i t y to control variables; to keep a l l but one variable the same so the effect of one variable can be investigated. According to Piaget, as cognitive maturity i s attained i n a variety of concepts there i s a s h i f t i n the reasoning about re a l or observed events to reasoning about a l l the possible events i n a given s i t u a t i o n . The less mature pupil i s limited to reasoning about the s p e c i f i c content of the problem because he cannot generalize and apply an organizational p r i n c i p l e learned about one variable (e.g. length) to another variable (e.g. weight). In contrast, cognitive maturity brings the capability of organizing any data, even verbally presented information, by using generalized p r i n c i p l e s . The pupil can separate the individual variables of the problem and consider the possible effect each variable might have. When the pupil reasons about these p o s s i b i l i t i e s , he i s not dealing with the objects themselves, but with t h e i r "truth values". The pupil must therefore use propositional l o g i c . In agreement with Inhelder and Piaget (1958), Treagust (1979) argued that propositional l o g i c i s a fundamental part of formal reasoning. Inhelder and Piaget have observed that the pupil who has obtained formal operations can use 16 operations of propositional l o g i c . Of these 16 operations the biconditional ( 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 ind 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 position to compare the expectations with actual r e s u l t s . P r o b a b i l i s t i c and proportional reasoning should develop only after biconditional reasoning as they involve more complex operations such as -30-mentally formed relationships and comparisons. The a b i l i t y to form relationships and comparisons i s propositional l o g i c and i s essential for the success i n the s k i l l of co n t r o l l i n g variables. However, Ennis (1975), i n an analysis of Piaget's schema, showed that the a b i l i t y to "handle propositional 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 children from adolescents. Some of the complex operations are used correctly by seven and eight year olds, others are used poorly by adolescents. Ennis concludes "there appears to be no connection between i s o l a t i n g variables and possessing the combinatorial system". Further support for the inadequacy of the 16 operations i n explaining formal operations comes from Osherson (1974). Using a series of related l o g i c a l problems the research attempted to predict success and f a i l u r e based on which operations were needed to solve each problem. He found t h i s approach inadequate for predicting patterns of success i n individual subjects. I t i s possible that the concept of a controlled experiment develops early i n what Piaget c a l l s the concrete stage of development with the idea of a f a i r comparison. Fairness i s an essential concept required i n the control of variables. Wollman (1977a) found that students remain unaware of general c r i t e r i a of fairness even when they are capable of correctly judging a variety of comparisons as f a i r or unfair. Also lacking was a clear idea of how to explain or determine the causes of an event. Students were found not to analyze the event i n terms of a complete set of variable s . Even when these are s p e c i f i e d , they do not then systematically determine the roles of the variables by varying them one at a time. Piaget's formal stage i s supposed to 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 project 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 pupils how to i s o l a t e variables and the need for controls i n s c i e n t i f i c investigations. This study concluded that children automatically and progressively a t t a i n the a b i l i t y to i s o l a t e variables 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 transfer of reasoning from one pa r t i c u l a r problem to another was s l i g h t . Key ideas presented i n other research (Wollman, 1977a, 1977b) suggests that 1) even very young children have acceptable strategies for solving some co n t r o l l i n g variables 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 analysis devised by Pascal-Leone (1970), Case (1974) obtained evidence supporting the contention that on the c o n t r o l l i n g variables task the s p e c i f i c performance may be l i m i t e d by the capacity for processing information. Case (1974) conducted a t r a i n i n g study i n which the separation of variables procedure was taught to seven and eight year olds. Responsiveness to t r a i n i n g was related to the match between attention demands of the i n s t r u c t i o n a l method and the working memory and attention capacity of the subjects. Case's subjects dealt with three informational items or three schemes at the same time. A s i m i l a r set of items for t h i s study could be: 1) Why does bacteria grow on X-1 plates? (X = the t o t a l number of plates) 2) I t could grow because the a i r l e t i n has bacteria -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 to 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 tra i n i n g programme was followed by those pupils successful i n dealing with the three information items. These pupils learnt to deal with an added information item. For example, 1) Why does bacteria grow on X-1 plates? 2) I t could grow because a i r l e t i n had bacteria 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 did not exceed capacity, t r a i n i n g was very successful, otherwise i t was not. Case's methods dealt with "chunking" of information items and making new items s a l i e n t . The subject becomes accustomed to taking account of t h i s . New 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 carefully analyzed. The learner's i n i t i a l knowledge l e v e l needs to be ascertained and learning a c t i v i t i e s l o g i c a l l y presented to bring the learner from his i n i t i a l state to the desired state. At each step i n the learning process care i s taken to minimize the information load on working memory. Case's approach d i f f e r s from that of most Piagetian influenced education researchers since there i s no attempt to 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 applies 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 is "chunked" to make salient items and that any new information is absorbed into a familiar background. Case believes that the ability to control variables may be context dependent. Therefore, i t is 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 differences between s c i e n t i s t s ' science, school teachers' science and school pupils' science (Gilbert, Osborne and Fensham, 1982) create dilemmas which require addressing i f progress i n science education, i n the area of concept acquisition, i s to be achieved. For many pupils 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 to make meaningful and worthwhile (Watts and G i l b e r t , 1983). Teachers attempt to promote conceptual change i n t h e i r classrooms toward more correct s c i e n t i f i c views. Much current research i n t o how t h i s 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, 1972; Lakatos and Musgrave, 1970). The conceptual change b e l i e f can be summarized as follows: 1) Individuals approach any inquiry with t h e i r individual prior 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 inquiry, 3) Inquiry, rather than being an accumulation of facts, i s the transformation of current knowledge, and 4) Rationality consists i n viewing new problems, ideas, and practices 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). Children have been encouraged to change t h e i r concepts by interacting -35-with t h e i r environment. Laboratory work appears to be a perfect opportunity for creating conceptual change. However, when attempts have been made to measure the learning taking place following p r a c t i c a l work, a rather pessimistic picture 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 eff e c t i v e as we might have thought. He found that i n many science classrooms 1) pupils tend to consider each lesson as an isolated event while the teacher assumed that the pupils appreciated the connecting l i n k between the lesson and the previous learning experiences, 2) pupils sometimes invented a purpose for the lesson which was subtly but s i g n i f i c a n t l y different from the purpose intended by the teacher, 3) pupils often showed l i t t l e interest i n , or concern about those features of an investigation which the teacher, or textbook write r , considered to be c r i t i c a l s c i e n t i f i c design features, 4) pupils' knowledge structures, against which learning experiences were considered, were frequently not the structures the teacher assumed pupils had, and 5) pupils' understandings, developed from the outcomes of experimental work, were frequently not those that the teacher assumed were developed. Tasker (1981) also found that pupils are more concerned with deciding what to 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 pupil p r a c t i c a l work i s supported by Johnstone and Wham (1982). Pupil concern with the physical tasks of the experiment may be the resul t of assessment procedures rewarding well-written laboratory accounts, but omitting credit for pupils' statements about how - 3 6 -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 unfair since t h i s may be the inevitable 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 and organized by laboratory texts and curriculum guides. From the teacher's point of view the material may seem to be w e l l explained and coherently organized. To the learner, the si t u a t i o n may look very d i f f e r e n t . The incoming information may have no apparent meaning as pupils could lack the conceptual structure to interpret t h i s new information. Freyberg and Osborne (1981) point out that children often misinterpret 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 willingness to construct meaning and test these against experience and structures i n long term memory i s c r i t i c a l i n terms of developing learner-generated meanings. Pupils have to be motivated to construct new meaning for concepts since t h i s often requires much mental e f f o r t . Motivation depends on individuals accepting a major r e s p o n s i b i l i t y for t h e i r own learning (Wittrock and Lumsdaine, 1977). Pupils 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?'; the pupil 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 pupils perceive a problem to be a problem and what i s to be learned to be worth learning, they w i l l not become active and committed i n t h e i r studies. -37-Another working hypothesis that has been advanced (Johnstone and K e l l e t t , 1980; Johnstone, 1980) i s that learning i s severely hampered i n a high information situation i n which the working memory i s overloaded with incoming data. The term working memory i s used to describe the area of memory that i s sorting and processing information into short term or long term memory. Posner (1982) also talks of a "problem space" and the f a c i l i t y of memory to create t h i s space. "In many problems, setting up the problem space leads to the establishment of one or more goals to be achieved" (Posner, 1982). 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 with s i m i l a r problems and hi s framework of the concept as an a i d . The mental a c t i v i t y that pupils engage i n to construct meaning and test constructions against sensed experience and structures i n long term memory are the resul t of motivation. Motivation i s closely t i e d to intentions, plans and previous experience and r e l f e c t s more than momentary environmental stimulation. Attention to the p r a c t i c a l task i s influenced by aspects of long term memory and cognitive processes. Attention becomes sel e c t i v e due to these past experiences and therefore results i n selective perception. Attention involves both attending to the unexpected and a sustained interest i n the experience and requires volu n t a r i l y controlled e f f o r t (Wittrock, 1981). In order to construct meaning from the sensory information provided by the experiment, l i n k s need to be generated to 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-learner i s required to 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 and Larkin, 1980). These include: 1) reconsidering 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 aspects of memory store to the sensory information, 2) considering the p o s s i b i l i t y that unfounded assumptions were used as a basis for attention and s e l e c t i v e perception, 3) attempting to l i n k d i f f e r e n t aspects of the sensory information to memory store, and 4) systematically considering a l l possible l i n k s to d i f f e r e n t aspects of long term memory i n an attempt to construct meaning. I t i s conceivable, however, that these a l t e r n a t i v e strategies could y i e l d d i f f e r e n t views of the phenomena being studied. Although i t may be p l a u s i b l e , as some have suggested, that c h i l d r e n and s c i e n t i s t s construct 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 experiences, the views chi l d r e n generate are often very d i f f e r e n t to those of s c i e n t i s t s . Osborne, B e l l and G i l b e r t (1982) suggest a number of possible reasons for t h i s : a) Children tend to view things from a s e l f - c e n t r e d or human-centred point of view and tend to consider only those e n t i t i e s and constructs that follow d i r e c t l y from everyday experiences, b) Children's experiences of the world are 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) Children tend to be interested i n p a r t i c u l a r explanations f o r s p e c i f i c events and tend not to be concerned with the need to have mutually coherent and non contradictory explanations f o r a v a r i e t y of phenomena, and -39-d) The everyday use of language tends to be subtly different from the language of science, p a r t i c u l a r l y with regard to basic and important words, l i k e "animal", " f r i c t i o n " , and "force", and these everyday meanings tend to shape children's constructions. Research conducted to date suggests that children's ideas related to science concepts can remain unaltered since science teaching has not encouraged conceptual change. Children may have no r e a l motivation to change thei r conceptions. Symington (1981) found that children who could provide the i r own reasoning for an everyday phenomenon tended not to be interested i n what other pupils had to contribute as an explanation of that phenomenon - they already had an explanation that was perfectly satisfactory to them. An understanding of some aspects of current s c i e n t i f i c thought would seem to require a major restructuring of children'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 fellow student. Sometimes the change i f far from that envisaged by the teacher. Examples can be found where older children have ideas which appear less congruent with the views of s c i e n t i s t s than the views of younger children (Osborne, 1981; B e l l , 1981; Gunstone and White, 1981). Tasker's (1981) findings concerning classroom experiences implied: 1) meanings are frequently generated by pupils which are substantially d i f f e r e n t to those hoped for by teacher, textbook w r i t e r , or curriculum developer, 2) lessons are not linked by pupils to the appropriate knowledge from -40-previous lessons, 3) pupils generate a purpose for a learning a c t i v i t y which i s d i f f e r e n t to 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 to be made, to s c i e n t i f i c patterns of thought i n memory to ensure that f u l l consideration i s given to 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 to generate meaning from a learning experience are sometimes inadequate, or inappropriate, and t h i s leads to non s c i e n t i f i c outcomes. Freyberg and Osborne (1981) indicate that i t i s easy for pupils to make l i n k s to 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 pupil to f i n d l i n k s between knowledge i n long term memory and incoming information, or to construct meaning and evaluate t h i s meaning against t h e i r own experiences. Teachers are unlikely to view laboratory work as obscure, meaningless, isolated events since they are able to construct meaningful l i n k s between the knowledge structures provided by the previous lesson and those concepts that are to be presented i n the next lesson. I t i s more probable that teachers have considered the problems caused by detailed laboratory work and the amount of information that pupils have to deal with i n the form of written instructions, verbal instructions, r e c a l l of manipulative s k i l l s , etc. More thought needs to be applied by teachers i n the area of l i n k i n g the incoming information to knowledge structures held by the p u p i l . This necessitates teachers knowing the substantive b e l i e f s of the class and how the pupils are going to view the laboratory event and use the incoming information. -41-2.3 Educational implications The b e l i e f s that pupils bring to the science laboratory are often at variance with those that teachers wish them to hold. A transformation of these alternate viewpoints into viewpoints more acceptable to 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 strategies that promote c o n f l i c t with the pupils' b e l i e f s . Laboratory work i s often used by teachers to promote concept learning, 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 isolated events and l i n k s between the concepts they should provide and theory work are often not formed. Pupils often do not know how to solve some of the problems i n experiments due to t h i s poor l i n k i n g of concepts or the i r lack of knowledge structures. Existing personal frameworks can therefore have a great influence on concept learning. Preconceptions, alternative frameworks or children's science are a l l terms re f e r r i n g to a person's e x i s t i n g conceptual framework. They "are amazingly tenacious and resistant to extinction" (Ausubel et a l . , 1978) and can often interfere with intended learning 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 well take be assimilated into the pupil's own framework but continue to be at variance with accepted s c i e n t i f i c conceptions. Teaching attempts to promote accomodation to new concepts. The term "accomodation" i s taken from Piaget's (1964) theory to denote what happens i n the student's mind as he modifies h i s preconceptions to reach consonance with the perceived data. Accomodation, then, requires -42-recognition by the learner of different views of concepts which cannot be readily accepted with the i r existing conceptions. According to Hewson (1980), i f children 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 unsatisfactory in 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 for the pupil to change viewpoints. Children need an alternative 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 consistent, 2) plausible i n that i t i s reconcilable with other aspects of the child's view, and 3) f r u i t f u l i n that i t i s preferable to 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 to be less i n t e l l i g i b l e , plausible, and f r u i t f u l than the pupil's own view (Osborne, B e l l , and G i l b e r t , 1982). The less i n t e l l i g i b l e , plausible 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 to construct meaning from new views and l i n k them with ideas i n memory that w i l l develop a useful and sound understanding. Pupils need to f e e l that generating new meaning i s worthwhile and successful. Often what i s required i n the learning of science i s the restructuring of existing ideas so that pupils see things from a different framework. This personal restructuring has been likened to Kuhn's (1970) description of a major paradigm s h i f t (Walters and Boldt, 1970). This may be achieved by showing pupi l s the inadequacies i n t h e i r present conception and providing them with linkages and alternative frameworks which w i l l help toward generating new and useful -43-ideas. New frameworks can simplify 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 children's views of a science concept. The teacher also needs to be able to assess whether or not a certain conceptual change i s a reasonable teaching goal with a s p e c i f i c group of pupils. Tasks need to be provided so that a pupil may c l a r i f y t h e i r own view about the part i c u l a r phenomenon under discussion. Pupils need the opportunity to debate the pros and cons of t h e i r e x i s t i n g frameworks with 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 for 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 "naturally i n v i t e a student to explain i t i n terms of his own preconceptions". Explication of pupils' preconceptions involves developing an atmosphere which enables students to make e x p l i c i t t h e i r own frameworks. Their productions might be verbal using class or small group techniques (Gilbert and Osborne, 1980; Nussbaum and Novick, 1981), i n written from (Watts and Zylbersztajn, 1981), presented graphically (Pope, 1981), or some combination of these. Pupils should be encouraged to state th e i r ideas cl e a r l y and concisely. This process encourages attention (Osborne and Wittrock, 1983) i n that pupils are aroused to defend t h e i r own ideas and concentrate on relevant issues. The learning environment i n which discussion takes place needs to be supportive and appreciative of the r i s k pupils take i n disclosing personal -44-ideas. Where the s c i e n t i s t ' s view of a concept i s not represented i t may be appropriate for the teacher to introduce the s c i e n t i f i c viewpoint as an alternative view. For the s c i e n t i f i c view to be considered seriously i t needs to be introduced i n a way which takes into account the views pupils currently hold. 2.32 Laboratory work I f teachers examine the presentation of laboratory work they find methods that can be improved so as to aid the pupils' l i n k i n g of concepts with new conceptual information. When we develop a general concept i n lessons we often begin with a single 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 st a r t i n g points lead to or obscure the main point we try to make. To reduce t h i s problem we could adopt three ground rules: 1) Give a clear statement of the point of the experiment, 2) State c l e a r l y what i s preliminary, peripheral, and preparatory, 3) Avoid possible overload of information by t r y i n g to teach manipulative or interpretive s k i l l s at the same time as data i s being obtained. Lawson (1983) suggests that without establishing a direct connection between hypothesis and experimental r e s u l t s , via predictions already based on e x p l i c i t l y stated hypotheses, the force of s c i e n t i f i c experimentation as a means of generating knowledge i s weakened. I t i s recommended that a l l experiments should be conducted and reported with not only a statement of hypotheses tested and results obtained, but with predictions generated as w e l l . During the experiment the pupil can experience d i f f i c u l t y r e l a t i n g to the main point of the experiment and the relevance of incoming sensory information. When the pupil can "chunk" incoming information 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 is 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 is 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 study. 2.33 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 of the problem to th e i r knowledge structures. This i s either due to lack of linkages or inadequate knowledge structures. Research into problem solving does not appear to 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 useful to think of problem solving as a "single, uniform c a p a b i l i t y " and strategies devised to a t t a i n a general problem solving s k i l l " i s p r a c t i c a l l y hopeless at t h i s stage of our understanding" (Greeno, 1977, p. 17). Problem solving appears to be highly content s p e c i f i c . Michael Polanyi (1967) points out that much of human knowledge i s " t a c i t " i n that, under ordinary conditions, i t can be explicated i n words. Perhaps t h i s applies to the s k i l l s of problem solving as Larkin (1979) explains: " i f these t a c i t processes remain unexplicated, then, to help a beginner learn, there i s l i t t l e one can do beyond providing examples and practice, 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 to b u i l d e x p l i c i t models for formerly t a c i t processes then i t becomes possible to teach these processes, either d i r e c t l y or through appropriately selected practice and example. In addition e x p l i c i t models for t a c i t processes can aid i n i d e n t i f y i n g and remedying errors i n the developing s k i l l s of learners." I f we want to improve problem solving a b i l i t y i n schools we could begin by analyzing the kinds of problems children are asked to solve. Elkind (1972) takes the position that instruction i n controlled experimentation generally should not be introduced u n t i l adolescence. In contrast Lawson and Wollman (1976) suggest a very gradual introduction and continued reintroduction of lessons involving concrete materials and a c t i v i t i e s to enable students to make comparisons and judgements. Wollman (1977b) suggests that a variety of experiences providing situations to develop a general procedure may be useful since research on memory confirms the positive value of 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. Understanding the separate parts is not sufficient. Time is required for integration of the parts. Not only is 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 is 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 is 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 of study 3.1 Introduction The recent publication of numerous research studies, with t h e i r focus on the learner's cognitive structure, represent a major s h i f t i n the role and status given to the learner i n the educational process. By using quantitative 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 issuing from the interpretive 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 , ungeneralizability and subjectiveness. Power (1976) describes such studies as ideographic. In these studies students' conceptualizations are analyzed on t h e i r own accord without reference to "an externally defined system" (Driver and Easley, 1978). C l i n i c a l interviews and case studies are often i n the ideographic t r a d i t i o n . Supporters of ideographic studies have moved towards personal, f l e x i b l e , interview techniques (e.g. Pines, 1979; Pines et a l . , 1978) with loose a n a l y t i c a l forms of conversation used to id e n t i f y student perceptions and construct a conceptual inventory. In contrast "nomothetic studies" assess students' understanding " i n terms of the congruence of th e i r responses with 'accepted' s c i e n t i f i c ideas" (Driver and Easley, 1978). Since these methods are often quantifiable, Power (1976) sees them as a r e f l e c t i o n of 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 also -49-ch a r a c t e r i s t i c of many researchers engaged i n mapping cognitive structure (e.g. Deese, 1965; Shavelson, 1974; Preece, 1976) using various forms of word association techniques. Considerable disagreement exists over tine appropriateness of these two methodological stances. Different 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 to reject 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 quantitative methods but also on the clash of methodological paradigms. As R i s t (1977, p. 43) states "Ultimately, the issue i s not research strategies per se. Rather the adherence to one paradigm as opposed to another predisposes one to view the world and the events within 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 "direct inspection on r e a l i t y " . People have used different ways i n order to put constructions on r e a l i t y . I t has been argued that paradigmatic characterizations influence constructions on r e a l t i y . Pepper (1942) believes that understanding the different approaches used i n interpreting r e a l i t y i s aided i f one distinguishes between the four "adequate" world hypotheses of formism, mechanism, contextual ism and organism. Linking 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 resort to a r i g i d and fixed approach since the three a n a l y t i c a l devices Pepper uses to describe and compare the world hypotheses provide different orientations for research. Paradigmatic characterizations, those of the q u a l i t a t i v e methodology being phenomenological, inductive, h o l i s t i c , subjective, process orientated and of a s o c i a l anthropological world view, are based on two assumptions (Cook -50-and Reichardt, 1 9 7 9 ) . Firstly, i t is assumed that a method type is irrevocably linked to a paradigm and secondly that the quantitative and qualitative paradigms are assumed to be rigid and fixed. Cook and Reichardt (1979) argue that these points should not be assumed. No discipline is 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 developed for the task of discovery and generating hypotheses. 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 is 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-Sheffler 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 to constructs such as discovery and inquiry, which are used extensively i n science education. The linkage that exists between paradigm and method can usefully guide one's choice of research method, but the research situation i s also an important factor. 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 claiming that groups or individuals studied only once with a t o t a l absence of control 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 revised his position and acknowledges their usefulness i n educational research (Easley, 1977). Although one of the strongest arguments against these ideographic studies i s t h e i r lack og g e n e r a l i z a b i l i t y , Cronbach (1975) suggests that "we reverse our p r i o r i t i e s because the observor i s appraising practice i n i t s normal setting and observing i t s effects i n context". 3.11 Background to methods used i n the study Any research programme with aims to enhace teaching and learning i n the classroom must have meaning and f i l l the needs of the involved pract i t i o n e r s . Recognizing t h i s P a r l e t t and Hamilton (1977) and Stake (1974) established classroom research with emphasis on what was going on i n the educational setting where the needs of the participants are given prominences. A further s h i f t has then been to pay more attention to 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 al., 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 al., 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 difficult for the pupils whilst selecting definitions, although quantifiable and easier, may s t i l l not provide the dynamic quality of thought. Using methods involving bipolar dimensions may not be useful in the classroom due to their application difficulties and the skills required in analysis. As Fensham et al. (1981) point out, i f research procedures were to -53-become part of the regular pattern of teaching and learning i n science classroom they would have to meet a number of c r i t e r i a focussed on issues such as: 1) the amount of inst r u c t i o n a l time required, 2) congruency with teacher behaviour, 3) providing tasks within the a b i l i t i e s of students and teachers, 4) teachers are able to use i n t e l l e c t u a l s k i l l s and procedures involved i n data gathering and analysis, 5) analysis and data meeting the requirements of the teacher, and 6) learning w i l l be helped as a re s u l t . With many of the above c r i t e r i a i n mind and considering the teaching sit u a t i o n the c l i n i c a l interview and other descriptive ethnographic techniqes were used to c o l l e c t some of the data for 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 following two sections. 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 largely from Piaget's (1929) work and has been used extensively to fi n d children's responses to a variety of physical phenomena. The interview has been defined as "a conversation directed to 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 et a l . , 1959, p. 3). The purpose i s fixed i n the investigator's mind and i f care i s not taken may lead to the "situation of interviewer seeking information from interviewee, and at the other (end) a troubled interviewee seeking help from the interviewer" (Posner and Gertzog, 1982, p. 195). - 5 4 -The clinical 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 itself to superficial observations, but aims at capturing what is hidden behind the immediate appearance of things" (Piaget, 1926, pp. xiii-xiv). Pines et al. (1978) have produced much work using clinical interview techniques. It is 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 field by the researcher and its 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. Eliciting these original conceptions is achieved by semi-structured question framework. This framework is made up of questions that are general enough to be placed in a variety of places within the interview. The questions open-ended 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 - 5 5 -et a l . , 1978). Conversations overcome the reluctance on the part of the subjects to respond f u l l y i n writing to questions. However, there are d i f f i c u l t i e s i n obtaining q u a l i t a t i v e data using the interview. The interviewer has to r e a l i z e the danger of allowing h i s preconceived ideas to lead to suggestions that the student may take up, thereby obtaining misleading data on the child's genuine ideas. Nuances i n phrasing, a particular word, or the selection and ordering of queries can a l l stimulate suggested convictions. After the interview, transcripts are made from the recorded interviews and these become the basis for l a t e r analysis. 3.13 Classroom data The classroom teaching s i t u a t i o n has more potential to d i s t o r t the students' responses toward a more 'accepted' school view of the topic area under consideration than the c l i n i c a l interview setting. 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 collected. 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 with different small groups of pupils on a variety of topics he concluded that small group work allows discussion, recording of experiences with speech being used to communicate or r e f l e c t thoughts. Gagne and Smith (1962) have also indicated t h e i r support for student verbalization for c l a r i f y i n g t h e i r ideas. Barnes (1979) found that pupils tend to organize thoughts on a -56-clearer basis for fellow pupils than they do for teachers. This seems dependent on the knowledge of the audience; the less knowledge the audience i s expected to have then the more e x p l i c i t the explanation. He also found that taped discussions of children working on t h e i r own on a problem that had been cle a r l y defined produced transcripts with examples of "exploratory speeach". The ta l k i n g out of problems, rearranging of , ideas and tentative moves towards hypotheses were seen as relevant to the pup i l . Occasionally the interviewer i n the c l i n i c a l setting may perceive something as irrelevant whereas the student sees these ideas as important to his "framework". Groupwork may be a safety net to catch these ideas. Once children have become used to explaining t h e i r groupwork to a tape recorder the "exploratory speech" may r e f l e c t more of the nature of the children's ideas than would a more formal s e t t i n g , such as an interview or a large class discussion, which would normally produce a "formal" response. In many examples shown by Barnes and Todd (1975) the pupils discussed questions posed on a task card. The task had been cle a r l y explained, pupils had been introduced to the equipment and shown how to operate i t . These researchers were anxious to preserve i n th e i r analysis of the resul t i n g conversations the features of children'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 pupil's own knowledge would be conserved. This i s essential since the structuring of concepts i s thought to 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 skills 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 clinical interview to obtain the pupils' beliefs concerning bacteria (interview one) took place prior to the introduction of the topic in the first half of the second school term. This involved thirty-one pupils. -58-In the second half of the term the topic of "bacteria" was introduced using the two experiments in the study. 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 Between class Class period 2 Task set up experiment 'Bacteria in the air' group discussion of experiment Data Gathering Method small groups taped during experiment individual clinical interviews (interview 2) (9 pupils) small group discussions Group 1 A (4 pupils) Group 1 B (3 pupils) 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" Time Class period 3 Between class Class period 4 Task set up experiment 'Bacteria on Ourselves' group discussion of experiment Data small groups taped Gathering during experiment Method Group 2 A (2 pupils) Group 2 B (3 pupils) individual clinical interviews (interview 3) (9 pupils) small group discussions presentation of overhead materials laboratory write up centred on specific questions 3.3 Decription of the clinical interviews Each pupil's ideas were recorded on tape for the first i n i t i a l interview. Whilst every pupil willingly participated in the interviews, the researcher felt 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 first 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 tell? 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 its 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 did we have clean hands at the st a r t of the experiment? 4) Why did we have a plate for a draughty place (plate 1) and a draughtless place (plate 2)? 5) Why did we have to open the dishes for so long? C l i n i c a l Interview Three The purpose of t h i s interview was to e l i c i t the understanding of the experiment and i t s r e s u l t s , 'Bacteria on Ourselves' (Experiment 2). The whole class carried out the experiment according to instructions reproduced from the Combined Science Text. Again the pupils worked i n small groups and afterwards considered questions concerning the method of the experiment. These questions formed the basis of the the t h i r d c l i n i c a l interview. Nine pupils were interviewed; the following questions are t y p i c a l of an interview: 1) Why do you think we had plates A and B? 2) What do you expect to see on these plates? 3) I f there weren't bacteria on plate C what was the purpose of having plate C? 4) Does i t r e a l l y matter that a l l the plates were s t e r i l e at the beginning of the experiment? 5) Why did we put plates i n the incubator? 3.31 Description of the taped small group discussions The taped small group discussions involved four groups of pupils 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 felt 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 girls. 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 - 6 3 -experiment two "Bacteria on Ourselves". Group A consisted of two girls; their third member of the class being absent. Group B was made up of three boys. 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. All 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. None of the pupils had had any formal teaching concerning microbes. In the first term a l l had learnt to use microscopes and taught some basic concepts of cells. Their first year curriculum had included work on living things. All the members of the class were involved in the first clinical interview. In the second and third interviews approximately one third of the class was used in each case. Pupils selected for group work made up the third portion of the class. The schedule is summarized below: TABLE III Number of pupils involved in interviews clinical interview -1st 2nd (1st experiment) 3rd (2nd experiment) number of pupils 31 9 9 groupwork 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 left 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 first 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 its 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 is 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 flexibility. -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, clinical 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 clinical interview situation by the researcher to make sure that he/she is pursuing the line of thought of the subject and not his/ her own. During analysis of data derived from the clinical interview there is 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 clinical 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 with categorizing children since they "exhibit responses c h a r a c t e r i s t i c of many categories irrespective of the category system used" (1977, p. 192). In h i s analysis he attempted to reduce the interviewee's discourse to manageable units while at the same time preserving i t s i n t e g r i t y . This system of "conceptual propositional analysis" (CPA) was designed to elucidate "substantive content, indicating cognitive d i f f e r e n t i a t i o n and enabling the comparison of discourse analysis" (Pines, 1977, p. 74). The CPA process could act to increase the danger of f a i l i n g to recognize suggested convictions by including i n children's responses phrases taken d i r e c t l y from the investigator's questions. Although the basic sense of the discourse i s maintained, the origins of certain concepts and association become unclear. 3.52 Analysis used i n the study As mentioned i n Section 2.21 the concept map i s a device' to e x p l i c i t y represent a number of concepts, they can also be used to determine the framework of pupil b e l i e f s toward t h i s subject matter. Concept maps have application i n the teaching of a l l sciences at a l l l e v e l s and can provide the teacher with much valuable information. A concept, then, i s a set of relations among other concepts. The quality of the concept i s due to the relations with other concepts. The map i l l u s t r a t e s - t h e data base present i n the pupil's long term memory (Preece, 1978) and the propositional relations between the concepts at that one particular time. The terms i n the boxes are concepts and the verb or l o g i c a l connective constitutes a propostion. "The nature of a person's understanding of a concept changes as i t i s associated with a wider array of concepts and s p e c i f i c -68-propositions" (Malone and Dekkers, 1984). Based on Ausubelian (1978) learning theory i t would be anticipated that concept maps demonstrating meaningful learning would possess an organization of concept d i f f e r e n t i a t i o n ranging from the most general, more in c l u s i v e concepts at the centre to more s p e c i f i c and less i n c l u s i v e concepts at the perimeter. Examples of pupils' concept maps are shown i n Appendix A2. Pupil's propositional 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 of the concept map for that p u p i l . Using these propositional statements, and with the a i d of the concept maps constructed from them, the substantive b e l i e f s held by the class concerning bacteria were obtained and summarized. In order to detect the b e l i e f s pupils held concerning the two experiments being studied propositional statements supplied by the interviewed pupils were again isolated. These were also used to compare with the substantive b e l i e f s obtained from the f i r s t interviews i n order to detect any general conceptual change. I t was f e l t necessary to extract statements from the interviews as close to the o r i g i n a l pupil statements as possible since i t was thought essential to capture the subtle meanings of each statement. Although concept maps were used i n the f i r s t instance to i s o l a t e substantive b e l i e f s i t was thought that the propositional l i n k s between concepts provided i n the interview were not s t a t i c and showed signs of f l e x i b i l t y that a concept map could not display. To lend support to interview data extracts from group work and written 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 is 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, firstly, necessary to extract the substantive beliefs pupils held concerning bacteria from the first clinical 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 clinical interviews two and three. The three clinical 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 is 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 is true to the pupils' recorded speech. The nature of this pupil speech is truncated and hesitant and in many cases the sentence construction is 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 ini t i a l clinical interview. This first 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. Only one pupil used the colloquialism "bugs". 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 come there is such a difference between colds? Sharon: Types of germs. Int: How could you t e l l they were different types? Sharon: 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). All 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 in 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 in the blood, do they? Deborah: Yes. Int: If there is 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: If 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 lot 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 micro-organisms 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 air 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 first clinical 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 first clinical 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 is to these sources that this section is 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 bit 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: 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). Int: Where did you learn about white corpuscles? Lewis: I watched a program on telly. Others had had discussions with respected authorities such as dentists. It is 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 visit 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 live. 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: 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. Lee: 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 is 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 is 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 Air" 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 All 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. Excerpts from both interviews are included: -79-Clinical Interview One: Steven: It (the bacteria) divides every twenty minutes doesn't it? It 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 is 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 is the significance of the sterile equipment and medium? and 2) What is the significance of the control plate? Typical pupil responses of how the experimental procedures can be interpreted in 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 All 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 air. Nicole provides a response that is typical of the type of arguments used: Nicole: If i t (the agar) wasn't clean you wouldn't have the bacteria that you wanted because you'd already have something from the air 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 itself, 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. the airborne bacteria. 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 is occurs is not well understood. The relationship between the bacteria and the glass dish is 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 jelly 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 jelly. 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 air. In his first interview he stated that bacteria live inside living structures e.g. teeth and the throat. This appeared to be, for him, a requirement for them to live and multiply. In this instance he suggests that bacteria could be on the agar jelly, but he doesn't view any bacteria on the glassware as being important. This suggests that he does not believe that the bacteria are living 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 is 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. The following excerpts from transcripts show this: Question: How could we t e l l that there aren't any germs in that jelly 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: If you put i t in the pressure cooker i t i s bound to get r i d of the bacteria because of the steam and the pressure. It appears that although pupils accept the idea of airborne bacteria contaminating the agar resulting in 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 start of the experiment to confirm these sources of contamination. The time element i.e. waiting for the contaminant bacterial colonies to grow in the sealed plate proves to be problematic as these excerpts suggest: Question: How could we t e l l that there aren't any germs in that j e l l y when we started? Chris: Well i t (the agar) would be really clear. 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 ste 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 it s come out a l l blotchy and that. Andrew: They were sterili z e d . Int: How do you know that the ster 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 in time but does not relate this idea of growth to what could happen in the agar. The following transcript passage reveals this idea: Int: Could we t e l l i f the bacteria were in 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 in 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 itself and looked for other sources. These were again related to bacteria being in us and being breathed out as was the explanation in the first clinical 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 is necessary to completely understand the significance of the control plate. -84-Pupil significance of the control plate To ascertain how pupils viewed the control plate (plate 4) they were asked the following question: "Is there any purpose for plate 4? I f so what i s i t ? " I f pupils appreciated the significance of the control plate they would be able to reason that 1) the unopened s t e r i l i z e d plate with s t e r i l i z e d agar would not produce any bacte r i a l growth, even after f i v e days and that 2) t h i s would prove that no bateria could have come from the agar or inside 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 into plates 1,2 and 3 after s t e r i l i z a t i o n . Samples of answers to the above question follow: Steven: ...so that we could see i f bacteria seeped i n through the glass, 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 bacteria could get in t o plate 4 while i t was closed i n any way. Jonathon: ...see i f there were any bacteria i n the plate before we started. . . . i f the plate 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 . P h i l i p : You've got to get a l l of i t clean. Chris: I t ' s so you can compare the differences, so you can see how much more one's got to the one that wasn't open. -85-Michelle: We wanted to 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 difference 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 different colour to that and i t ' s just a l l one colour and you couldn't see any germs i n i t . You could just see what i t would be i n comparison with um the other two dishes but there's not r e a l l y a point for having plate 4. There were three major ideas produced by the answers to the question concerning the control plate: 1) That i t was to see i f bacteria could get into a closed p e t r i dish, 2) So that we can compare t h i s plate to the other three to see the amount of growths on the plates, and 3) To see i f there were any bacteria i n the plates before the experiment started. The f i r s t two major ideas were popular with pupils. Pupils especially l i k e d the idea of comparing the absence of bacteria i n plate 4 with bacteria present i n plates 1,2 and 3. At least with t h i s idea confirmed to themselves that the experiment had worked! The pupils who held the t h i r d idea (two, i f P h i l i p ' s previous statements are included) did not say how plate 4 could show that no bacteria were i n the p e t r i dishes after s t e r i l i z a t i o n and before the innoculation of a i r bacteria. They also were unable to state that t h i s plate would indicate a high probability that the bacteria from plates 1,2 and 3 were from the a i r . 4.23 Pupils' overall understanding of the experimental procedures Apart from s t e r i l i z a t i o n and control procedures, there were other instructions that had to be taken into account i n order to understand -86-the experiment and its results. All the pupils interviewed appreciated the need for washed, clean hands while handling the plates in order to prevent contamination in 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 in 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 in 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 is 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 left outside had more bacteria because there were more "germs" outside than in. The draughtless plate with the shield stopped germs getting in. Steven is 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 it's always draughty a l l the time. -87-I t was not appreciated that " l o c a l " wind speeds may be constantly varying and that by keeping the plates open for twenty minutes an average of the conditions was achieved. A l l p u p i l s claimed that the plates were open for longer than a few minutes i n order to allow enough bacteria to s e t t l e on the agar. The main problem with t h i s experiment was t r y i n g to show that the b a c t e r i a l source was s o l e l y from the a i r . Pupils saw the need for t h i s but f a i l e d to match up b e l i e f s with v i s u a l evidence provided by the c o n t r o l . In order to understand the control and i t s usefulness for eliminating sources of contamination the p u p i l s needed to appreciate that a l l b a c teria i n s i d e the plate were p o t e n t i a l contaminants since they a l l were l i v i n g and showing c h a r a c t e r i s t i c s of l i v i n g things. This was not appreciated by most students since pupils appeared to have vague b e l i e f s about the l i f e concepts of b a c t e r i a . In t h i s experiment pupils have revealed b e l i e f s concerning the l i f e of bacteria which suggests that the bacteria can be found i n the a i r , sometimes on the glass p e t r i dish, and sometimes i n the agar medium. However, bacteria are not always viewed as l i v i n g i n these environments since pupils do not always recognize that they are continually undergoing d i v i s i o n f or reproduction. I f t h i s concept i s held the bacteria on the glass are not mentioned as being important. A more l i k e l y explanation for possible contamination of the control plate would have involved bacteria seeping i n t o the closed dishes rather than the s t e r i l i z a t i o n process having f a i l e d and b a c t e r i a s t i l l being i n the plate as a l i v i n g , reproducing u n i t . The lack of l i f e concepts appear to play an important part i n p u p i l s ' understanding of the experiment. This w i l l be discussed i n more d e t a i l i n Chapter 5. -88-The third phase of the study involved a second experiment "Bacteria on Ourselves" which uses the same practical techniques and will 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 is reviewed in the first 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 All 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: All 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 in 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 is 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 is 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 is 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 its consequences as pupils see them is discussed in the next section. 4.32 Pupils' views on the significance of the sterile equipment  and medium All 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 first experiment, but also from the equipment. Several pupils provided examples of their beliefs as to why sterilization was done. Richard: 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. Sharon: They'd been sterilized so no dirt could be on them... you'd be able to see the colours of them. Mark: If 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 air. 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 lot 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 is 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 jelly because um it'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 is fully appreciated pupils should be able to cite plate C as proof that sterilization has been successful and that this in turn tells 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 is 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 volunteered, "... to show what the plate would look l i k e without any germs i n . " Sharon produced one of the more complex concept maps including the l i f e concepts from the f i r s t c l i n i c a l interview. She believed that bacteria reproduced " l i k e f a m i l i e s do". However, she apparently did not use t h i s concept of reproduction when discussing the purpose of plate C. Justine also claimed that plate C reminded us what the experiment looked l i k e i n the f i r s t place so we could see how much i t changed - a common idea presented by p u p i l s i n both experiments. She saw the need f or s t e r i l i z i n g the plates at the beginning of the experiment since she stated, "bacteria from other experiments might be on i t . " Although pupils viewed the need f or c o n t r o l l i n g contamination as important, the l i m i t e d number of pupils being able to prove that s t e r i l i z a t i o n had taken place r e s u l t e d i n s t i l l fewer p u p i l s having a f u l l understanding of the r o l e of the con t r o l plate i . e . that 1) plate C demonstrated that s t e r i l i z a t i o n had been successful, and 2) that i t eliminated contamination from the agar and glass so leaving contamination only occuring from the hands. I t i s possible that l i m i t e d l i f e concepts may a f f e c t the way p u p i l s view the experiment e s p e c i a l l y with reference to proving s t e r i l i z a t i o n has occured and the r o l e of the control plate. 4.34 Pu p i l s ' o v e r a l l understanding of the experimental procedures The pupils appeared to f i n d i t easy to make the corre c t predictions f o r the experiment even though they experienced some d i f f i c u l t y i n explaining t h e i r reasoning behind these predictions. Throughout the -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 lot of importance to the agar in its 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 is an indication that l i f e concepts are not very strong and may influence the pupils' judgement as to what is 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 its 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 is 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 Pupils' perceptions of the two experimental tasks The dialogue of two groups of pupils were recorded while they set up each experiment. The pupils were then asked to provide written answers to questions concerning the method of the experiment (provided i n Appendix E). Transcripts of recordings were then produced and analyzed for pupils' views on a) instructions being followed, b) actions being carried out, and c) re s u l t s . These are three aspects of laboratory work similar to those discussed by Tasker (1980). 4.41 Experiment one: "Bacteria i n the A i r " The f i r s t experiment "Bacteria i n the A i r " produced two transcripts 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 respectively. Group 1A The boys were quite comfortable being recorded and commenced recording when they were a l l seated and ready to s t a r t . The instructions on the printed work sheet were followed i n a recipe-type fashion with individual pupils reading out the instructions. I t appeared that pupils had glanced over the instructions before s t a r t i n g , but t h i s provided confusion since they did not obtain enough information about the general plan of the experiment. Features such as how long the agar plates were open were not questioned, but s t r i c t timing of how long - 9 6 -the plates were open was observed. This is 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 is. It says put the first 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 it? 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 is 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 is labelling up the plates) Mark: There, do i t on number two, do i t on the l i d of number two. Martin: What was in that one? Mark: Er. Martin: What was in that one? Was that the lid? Mark: The jelly, it's the jelly. Martin: What are we doing? Robert: What we are doing is testing for bacteria and we've got some jelly here. Mark: And on.the windowsill in the draught. Robert: We're testing the bacteria in the air. And here we're going to exclude (the) draught from the jelly and see... Mark: For twenty minutes. Steven: No, i t doesn't. Mark: It is. Martin: How are you going to test what bacteria's in that one? Steven: It's going to take two days. Mark: Well this will test i f there's bacteria in the air, won't it? Robert: Yes. Mark: And this will test to see i f there's bacteria just floating about and not in the draught. What is number three then? Mark states that the plates have to be left open for twenty minutes with the draught excluder, but he is unsure that i t will take at least two -97-day s, according to Steven, to obtain a result to the experiment. This confusion is 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 is 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). All 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 left open to see i f anything could get in although Mark did suggest that i t was left to see i f i t changed after being left 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 is that Steven suggests that the dirt and dust on the plates is bacteria, but he is not totally sure about this. The others are not convinced either and probably think that i f i t is 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: Let's have a look at (plate) number 3 . Mark: This is the worst one exposed to the most air. Robert: The one exposed to the most air Steven: Is that bacteria? Robert: The one exposed to the most air Steven: Hey look, is that bacteria? Martin: Or the draughtiest place. Robert: Of course it's bacteria. Later on in the transcript: Steven: It says you have to wait two days in an incubator. Mark: Just say what the results are now. Robert: Here are our results now after exposing our plates to certain whizzes and air. Steven: On plate one we have a swirl effect with minute pieces of dust. Robert: What was plate one, where was it? Steven: And plate one was outside our room near a draughty door. Mark: Plate 3 seems to have a lot 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 . Martin: Right, is that it? Robert: Yes. Group 1 B This group consisted of three girls. 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. - 9 9 -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: Here, just leave i t here or on the windowsill. Nadine: Just put i t near the window here. Nicole: Inside. Sally: Yes. Nadine: Ajar. Sally: Ajar. Nicole: Just a l i t t l e bit ajar. Sally: Half way. Nicole: Half way. Sally: The outside one should have been ajar, Nadine: No, i t shouldn't, Nicole: Half way. Nadine: 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 is 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 is 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 fair, would it? 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 will aid their - 1 0 0 -understanding by encouraging pupils to listen to other viewpoints. Nadine: Question 4, 'the plates were left 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 is a reason for i t , a purpose. Nicola: Yes. Sally: We reckon there is a purpose for i t . Nadine: We can't put reckon. Nicola: Yes, we think there is. Sally: It says what is i t i f there is 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 is 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 will do although i t is not certain that the statement answers the question correctly. Any internal conflict within Nadine is 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 fair 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 is 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 is an interesting move that the girls made. Obviously they did not appreciate that their discussion was of any value to the teacher. Perhaps this is a reflection of how they view their work and how they see a l l school work being assessed in its final form and not during its synthesis. Further discussion on these attitudes and others reflected from these group work transcripts is provided in Chapter 5. -102-Group 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 all 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 it 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 it took l i t t le 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: Do you think bacteria will grow on plate C? Michael: No. Andy: No, because.... Chris: No, because it hasn't been opened. Andy: Because it hasn't been, well it might have been. Chris: Yes, because the bacteria.... Michael: Plate C. Chris: I know, because the bacteria could be out (side), could get through to the plate. Andy: No, I don't think so. Chris: No, that's good. Andy: Just put no. Chris: Well I think it should. Andy: Well you're wrong. Michael: Two against one. Chris: 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: Why do you think we had plate C? Er, to.... Chris: Because we could. Andy: To see i f bacteria could grow in plates taped up? Michael: Yes. Chris: 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 is 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. These issues will be discussed in more detail in Chapter 5 . 4.5 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 is 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 first 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 first 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. All the pupils appreciated that our hands could introduce contamination into the plate, either in the form of "dirt", "germs", or bacteria. Two groups mentioned that the "germs" could spread onto the jelly. 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 jelly 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 is 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. All have assumed that sterilization was successful. 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 in this role ignoring the obvious that i t was easy to compare something in plates A and B against "nothing" in 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 first 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 fu l l extent of the sterilization procedure and how this is 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 is 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 will 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 will be discussed in the next chapter. -108-CHAPTER FIVE 5.0 Introduction This chapter discusses pupils' b e l i e f s about bacteria and examines the way i n which pupils' b e l i e f s concerning bacteria interact with t h e i r understanding of experimental procedures involved i n the two experiments used i n t h i s investigation. The chapter reviews pupils' use of prior b e l i e f s when id e n t i f y i n g bacteria on the agar plates, looking at colonies and t h e i r varying sizes, 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 role of the control plate. From the analysis of the data i t was found that some concepts are useful i n helping pupils 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 role of the control plate. Other pupils who did not possess the correct s c i e n t i f i c framework of these concepts were less successful i n interpreting the data obtained from the two experiments. Section 5.3 i s a discussion of the use that some pupil s make of th 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 role of the control plate. The analysis of group work transcripts and the written work produced by these groups revealed pupil attitudes towards laboratory work. The importance of these attitudes and pupils' p r i o r b e l i e f s i s discussed, with reference to teaching strategies, i n section 5.71. Suggestions for further research are presented i n the f i n a l section of the chapter. -109-5.1 Discussion of pupils' b e l i e f s about bacteria The i n i t i a l interview of thirty-one pupils produced pupils' substantive b e l i e f s concerning bacteria. I t was not surprising to discover that pupils have b e l i e f s about bacteria prior to formal instruction since the l i f e experiences of a c h i l d i n today's world would provide many learning opportunities, e.g. v i s i t s to the dentist or doctor, and watching t e l e v i s i o n . The concept of a bacterium i s not isolated from other concepts. The m u l t i p l i c i t y of the pupil's concept of bacteria can be seen as a set of relationships between concepts within a conceptual framework. To c l a r i f y the relationship between concepts and to graphically demonstrate the resulting framework, concept maps can be used (see Appendix A2). In each map there are many different concepts making up the composite b e l i e f of bacteria. Some concepts e.g. the concept "small" are well defined and present i n many of the pupils' 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 to the concept. This may be because the concept of " l i v i n g " i s not well understood, p a r t i c u l a r l y with respect to micro-organisms. Many pupils believed that bacteria were l i v i n g , but pupils' b e l i e f s about bacteria varied throughout the class because each pupil held a variety of related subsuming concepts that made up his/her b e l i e f s about bacteria. The meanings attached to the relationships between these subsuming concepts gave va r i e t y to the pupi l s ' conceptual frameworks. For many pupils the concept " l i v i n g " assumed a different meaning with respect -110-to the i r b e l i e f s about bacteria, but the heterogeniety of the b e l i e f i s a resu l t of the relationship between concepts i n the conceptual framework. Concepts make up the framework of pupils' b e l i e f s about bacteria. These concepts, as has already been stated, are not isolated from each other. Teachers could be more effective i f they recognize these concepts and researchers discover how they are related to each other. In the results section (4.1) i t was recorded that many pupils viewed bacteria as small microscopic "things" that cause disease. These diseases are thought to spread from animals or, more commonly, from people breathing, coughing and sneezing. I t was thought that d i f f e r e n t diseases were caused by different types of bacteria and some pupils reasoned that i n order for diseases to occur, bacteria must be a l i v e . A few pupils declared that bacteria had to be a l i v e to get into our bodies and to know where to go. Many pupils possessed alternative concepts of " l i v i n g " which were distinguishable 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 haracteristics were used. This supports Looft's (1974) findings that many pupils have an incomplete understanding of l i v i n g according to associated b i o l o g i c a l attributes such as n u t r i t i o n , respiration, reproduction, etc. The concept of l i f e has important meaning i n the way pupils perceive bacteria to function i n the context of the two experiments studies. I t was anticipated (1.31) that the pupils' conceptual framework of bacteria might influence the pupils' 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 for the pupils to interpret them correctly, -111-pupils need to be able to use a number of concepts that make up the conceptual framework of bacteria. In both experiments pupils need to appreciate that bacteria are widely d i s t r i b u t e d i n the environment i f they are to predict the results of the investigations. Most pupils appreciated that bacteria are widely distributed since most claimed the widespread existence of bacteria i n the i n i t i a l c l i n i c a l interview. This idea i s necessary for understanding the p o s s i b i l i t y of contamination of the s t e r i l e p e t r i dishes and media used i n the experiments. Another concept required to understand how contamination might occur i s that of bacteria being l i v i n g units. Of the seven supporting concepts that contribute to the concept of l i f e , that of reproduction i s the most fundamental to these experiments since i f reproduction does not occur, the bacteria do not become v i s i b l e as colonies. The concept of reproduction can be used to explain the increase i n the s i z e of b a c t e r i a l colonies. Pupils may not be able to d i f f e r e n t i a t e between the growth i n the size of a b a c t e r i a l colony involving 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 of colony growth or the increase i n the size 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 to support growth and reproduction i n bacteria i s a prerequisite concept to understanding the l i v i n g nature of bacteria. Thus i t seems evident that pupils are required to have an understanding of a number of related concepts i n t h i s area before i t would be reasonable to expect pupils to understand the two experiments i n t h i s study. I f the pupil uses the term germ or bacteria i t places the pupil's mastery of the concept at 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 to give meaning to the concept by showing knowledge -112-of a l l the defining attributes of the concept promotes concept mastery to l e v e l f i v e (Klausmeier, 1976). Although a l l the attributes of bacteria 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 question. In order to reach mastery l e v e l f i v e for the concept of b a c t e r i a l l i f e the pupil would need to c l a s s i f y instances of n u t r i t i o n , excretion, s e n s i t i v i t y , reproduction, growth and movement. To understand these experiments pupils 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 bacteria. From the results obtained i t i s found that pupils commencing these experiments do not relate concepts of movement, reproduction, growth and n u t r i t i o n to ba c t e r i a l l i f e . These appropriate concepts were held by only two pupils i n the class and these were held i n r e l a t i o n to the general term " l i v i n g things" and not s p e c i f i c a l l y to bacteria. Other pupils did not possess any understanding of bacteria as l i v i n g organisms. In the i n i t i a l interview pupils were not asked about the continuity of l i f e i n bact e r i a l colonies, but Tamir et a l . (1981) reported that 45 % of his grade 5-9 sample of pupils understood the continuity of l i f e and 36 % realized that l i v i n g organisms originate from other l i v i n g organisms. This would be an important concept to hold i f one were to ask the pupils to predict the results of the f i r s t experiment. This task would be u n r e a l i s t i c for the pupils since only one pupil had previously seen bact e r i a l colonies. The i d e n t i f i c a t i o n of bacteria was not problematical for pupils since they showed that they had basic ideas of sorting things according to physical properties such as shape, s i z e , etc. The acquisition of sorting s k i l l s associated with 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 reinforced with everyday experiences. I t was also expected that pupils 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 syllabus. Pupils 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 re s u l t i n g data. The occurence of t h i s type of situation i s never intended by teachers. However, i n the researcher's experience, t h i s cannot be unusual since i t was the researcher's expectation that pupils would have reached higher l e v e l s of mastery i n the concept of l i f e as a res u l t of prior learning experiences and only through the i n i t i a l interviews were the concepts of bac t e r i a l l i f e found absent. The researcher's findings confirm Tasker's C1981) conclusions that pupils' knowledge structures, against which learning experiences occur, are frequently not the structures the teacher assumed pupils had. This would seem to compound patterns of teaching new concepts since the "building blocks" of the concept may not be there or, i f present, possess different relationships than those possessed by the teacher. In t h i s study remedial work was not embarked on and pupils commenced to use t h e i r knowledge i n the two experiments. The results of the pupils' endeavours to understand the two experiments are discussed i n the following sections. 5.2 Discussion of pupils' interpretation of the experiments i n the  study This section describes the role played by pupils' b e l i e f s as they relate to the pupils' attempts to interpret the experiments "Bacteria 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 respectively, which took place -114-after the pupils 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 interpretations of the f i r s t experiment the pupils i l l u s t r a t e d that they were able to ide n t i f y bacteria. The concept of many bacte r i a l c e l l s making up a colony seems to be held by many pupils. However, pupils found i t d i f f i c u l t to explain why the colonies varied i n siz e . Pupils were unsure of the purpose of the s t e r i l i z a t i o n procedure and the significance 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 re s u l t s . As a result of the absence of these "ideas" i t was not surprising that pupils did not understand the significance of the control plate since t h i s requires some understanding of 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 pupils 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 role of the control plate. In summary, pupils provided uniform predicted results for the second experiment. The pupils hypothesized that the "d i r t y hands" plate would have the most bacteria and a l l the pupils predicted that the control plate would be free from b a c t e r i a l colonies. Pupils believed that contamination of the plates was most l i k e l y to come from the a i r r e s u l t i n g i n a mixture of the airborne bacteria with bacteria obtained from pupils' hands. To prevent t h i s , the plates were not opened for more than a minute. However, i f airborne bacteria were l e t into the p e t r i dish pupils thought that i t would be possible to i d e n t i f y these from those from a pupil's hand by the colour of the bacteria. A l l the pupils -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 pupils 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 pupils offered methods of substantiating the s t e r i l i t y of the equipment. However, many pupils 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 after the s t e r i l i z a t i o n procedure. A l l pupils stated that the control plate would be free from bacteria, but some pupils s t i l l believed that bacteria 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 pupils claimed that the purpose of the control plate was to test 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 bacteria were not seeping into the p e t r i dishes. 5.21 Analysis of the concepts required to understand the experiments In both experiments pupils were required to 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 pupils had not had any previous experience i n i d e n t i f y i n g bacteria and so could not rely on t h e i r prior b e l i e f s to assist them i n i d e n t i f i c a t i o n . However, prior b e l i e f s about bacteria 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 bacteria on the plates. Concepts may influence the pupil'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 role of the control plate. 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 for s t e r i l e media and equipment the word s t e r i l e must have meaning for the p u p i l . The s c i e n t i s t would immediately -116-conclude that the medium did not contain any l i v i n g micro-organisms. Living organisms would be regarded as those that f u l f i l l the seven characteristics of l i f e . Pupils should also appreciate that any form of l i f e on the agar would be regarded as contamination and re s u l t i n unste r i l e conditions. Therefore, understanding the contamination of the agar and the p e t r i dishes requires the pupil to have concepts about bacte r i a l 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 nutrients to support l i f e . Evidence that the bacteria 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 essential subsumer concept i n the concept of bacterial l i f e . There i s also the possible contamination of s t e r i l e agar from unst e r i l e p e t r i dishes. S c i e n t i s t s understand that bacteria may spread onto the agar which provides support for l i f e . The s t e r i l i t y of the medium, agar and the p e t r i dish i s important and i t i s necessary to confirm t h i s i n order to be able to state from which sources the bacteria 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 control plate can prove the required s t e r i l i t y of the equipment and media. The underlying roles played by a variety of concepts related to the l i f e of bacteria has been discussed, i t i s now necessary to look at how the pupils' concepts of bacterial l i f e influence th e i r interpretation of the experiments. -117-5.22 Pupils' prior b e l i e f s  5.221 I d e n t i f i c a t i o n of bacteria Pupils had to i d e n t i f y bacteria 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 bacteria requires the pupil to correctly assign the organism to a d i s t i n c t group. Pupils were able to i d e n t i f y different types of bacteria from the agar by the colour of the colonies. In the i n i t i a l interview pupils did not use the c r i t e r i o n of colour for i d e n t i f i c a t i o n of different bacteria. Eight out of thirty-one pupils 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 bacteria before; they had actually seen any examples of bacteria. When i t becomes apparent that the microscopic world of bacteria i s smaller than pupils previously imagined shape as a c r i t e r i o n between dif f e r e n t bacteria loses 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 sort bacteria i n t h i s s i t u a t i o n and substituted the c r i t e r i o n of shape for another c r i t e r i o n that would allow vis u a l data to be more manageable. They used colour to separate bacteria that may be on pupils' hands from bacteria obtained from the a i r . This was suggested by pupils interviewed after the second experiment who were asked how i t was possible to d i f f e r e n t i a t e between bacteria obtained from sources such as the a i r , the agar, or from the hands. Their answer was probably enhanced by the variety of coloured colonies v i s i b l e on the plates used i n the previous experiment. Coloured colonies may have detered pupils from using the control plate to detect contamination from unst e r i l e agar. -118~ 5.222 The concept of ba c t e r i a l colony Analysis of transcripts showed that pupils were able to explain the concept of a ba c t e r i a l colony i n terms of the colony being made up .of many bacteria. Although pupils were able to describe a bacterial colony, they were unable to explain why the colonies varied i n s i z e . Pupils used t h e i r concepts of growth and reproduction, but they did not have s u f f i c i e n t mastery of these concepts to allow themselves any profitable insight to explain why colonies varied i n size . For example, Jonathon was unable to explain why some of the colonies were larger than others. His i n i t i a l interview reveals that he perceives bacteria as l i v i n g . He supported h is statement with b e l i e f s that bacteria feed on blood and that chemicals k i l l them. However, these are not concepts that can support an argument for different colony sizes. Another p u p i l , Steven, who had only one reason for bacteria being a l i v e was able to give a l o g i c a l reason to explain the different sizes of the colonies. Steven's concept consisted of bacteria reproducing themselves every twenty minutes. This was a useful conceptual springboard that enabled the question about varying colony sizes to be answered. P h i l i p also used his concepts revealed i n the f i r s t c l i n i c a l interview to answer t h i s question. A v i s i t to the dentist had resulted i n a discussion about tooth decay. P h i l i p revealed that bacteria "grow and s i t and multiply i n the teeth". He used his l i f e concept of bacteria multiplying to explain that bacteria could spread a l l over the agar. Concepts of bac 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 into broader conceptual frameworks i f they are able to provide acceptable explanations to questions. The explanations about bact e r i a l colony size appear to be related to -119- * how the pupils view the l i f e functions of the bacteria. Bacterial l i f e concepts are important since the size of the colonies i s related to the reproductive function of the bacteria. In the present study i t would seem that many pupils do not have s u f f i c i e n t knowledge of these l i f e concepts to be able to relate t h e i r b e l i e f s to the observations made i n the experiment. I t i s postulated that the concept of bacte r i a l l i f e i s necessary i n order to understand the spread of bacte r i a l colonies on the agar. 5.223 Pupils' concept of s t e r i l i z a t i o n The application of b a c t e r i a l l i f e concepts and i n par t i c u l a r those of growth and reproduction to support the significance 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 essential. From the analysis of answers to questions i n the three c l i n i c a l interviews there appears to be three categories of pupils. The largest group of pupils consists of those pupils who do not hold l i f e concepts related to bacteria and cannot support t h e i r reasons for 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 did not use them; the smallest group held the bac t e r i a l l i f e concepts of reproduction and used them to produce a v a l i d argument for the proof of the s t e r i l i z a t i o n procedure being successful. In the f i r s t experiment pupils who could not give adequate reasons to substantiate the success of the s t e r i l i z a t i o n procedure were found to have no concepts of bac 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 na t u r a l l y a success. However, a l l these pupils did appreciate.the reasons -120-for s t e r i l i z a t i o n . Perhaps more i n t e r e s t i n g are the speculative reasons as to why pupils of the second group did not use their prior concepts of ba c t e r i a l l i f e . Nicole was one of these pupils. Nicole's prior b e l i e f s about the l i f e functions of bacteria included a statement that bacteria were l i v i n g because they could be seen growing. The concept of growth i n colonies of bacteria i s required i n order to 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 pupil would have to understand the meaning of the word s t e r i l e . This would also e n t a i l recognizing that since the control plate was not opened there would not be any growth of bacteria i f the agar and p e t r i dish were s t e r i l e . I t would be expected that Nicole'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 to check for contamination of the plates by examining the agar with a microscope to see i f there were any bacteria. She may have been under the impression that growing bacteria can only be observed by using a microscope. The worksheet provided for the experiment stated that colonies of bacteria would e a s i l y be v i s i b l e to the naked eye after a few days. Analysis of the group work transcript showed that Nicole and her work colleagues had not read a l l the instructions to 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 did not record that bacteria may come from the equipment, Nicole speculated that since the control plate was unopened, contamination may be occuring through the "gap" between the l i d of the p e t r i dishes and th e i r bases and that the control plate would test for t h i s . In another example, Steven's l i f e -121-concepts supported him i n his concept of s t e r i l i z a t i o n , k i l l i n g the bacteria i n the p e t r i dishes and ridding the plates of unwanted bacteria. However, he did not use his concept that included ideas of b a c t e r i a l c e l l s d i v i ding to prove that the plates were s t e r i l e because the control plate was free from bacteria. Like Nicole he also though the the control plate would indicate i f bacteria were seeping through the gap or even the glass. Pupils learnt from the f i r s t experiment that bacteria are widespread i n the a i r and that these bacteria could be grown on the agar. Most pupils appreciated that there could be contamination of the plates by bacteria from unwanted sources. However, few suggested that the agar and the p e t r i dish could s t i l l be contaminated after s t e r i l i z a t i o n i f the process had not been completed properly. Only two pupils viewed the agar as a source of food but neither of these pupils 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 dish. I t appears that pupils did not connect the agar with any concept of l i f e and therefore no real need for s t e r i l i z a t i o n was seen. I t i s more understandable that pupils 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 pupils provided a s c i e n t i f i c reason for the success of the s t e r i l i z a t i o n process. They did so by using t h e i r concepts of ba c t e r i a l l i f e which other pupils did not possess. Two of these pupils argued that the control plate was used to prove the s t e r i l i t y of the plates before the experiment started. Nichola argued that bacteria would not grow on the plates i f the plates were s t e r i l e but did not relate t h i s proof of s t e r i l i t y to the function of the control plate. Many of the -122-pupils showed i n t h e i r written work that they could not establish i f the agar and the p e t r i dishes were s t e r i l e at the beginning of the experiment and possessed a l t e r n a t i v e perceptions of the control plate than those that would normally be held by the s c i e n t i s t . 5.224 Pupils' perceptions of the role of the control plate Most pupils viewed the role of the control plate as a comparison against other plates. Some pupils used i t to check i f any bacteria had entered the plate through the "gap" between the l i d and the base. The construction of the plates may have contributed to the ideas held by many pupils. In everyday l i f e the seal of a j a r i s expected to be tig h t i f things are to be kept i n or out. The glassware of the p e t r i dish i s loose f i t t i n g and may give the impression that a seal was absent. However, a l l the pupils had the opportunity to prove that bacteria were not entering the plates by t h i s method because at the end of the experiment the control plate was free from bacteria. Only Michelle used t h i s evidence to argue against the notion of bacteria seeping i n . Seven of the nine pupils interviewed i n the second experiment could not provide a proof of s t e r i l i z a t i o n and the control plate was s t i l l viewed as a comparison between other plates. The pupils with adequate ba c t e r i a l l i f e concepts concerned with reproduction or growth, at a m u l t i c e l l u l a r l e v e l , were able to j u s t i f y t h e i r reasoning for the s t e r i l i z a t i o n process and the control plate. Of the ba c t e r i a l l i f e concepts those of reproduction or growth concepts with reference to c e l l d i v i s i o n were the most useful. Some pupils added to t h e i r concepts through doing the experiment, but they often did so i n a less than -123-satisfactory way because these newly acquired concepts could not be used to generate the s c i e n t i f i c meaning for 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 his 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 learning has no hooks on i t : i t can't be attached to anything, i t i s no use to the learner" (Holt, 1975, p. 104). Experiments may change the relationship between concepts or add new concepts to 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 pupils with a r i c h source of concepts that may be interpreted i n different ways but we cannot guarantee that these new concepts are interpreted i n the same way as s c i e n t i s t s would interpret them 5.3 Pupil held concepts affecting the understanding of the experiments This section w i l l examine the effect that the concepts of s t e r i l i t y and growth have on a pupil's understanding of the experiment. The nature of these concepts may hinder or aid the pupil's understanding of the procedures used i n the experiments studies. 5.31 Pupils' concept of s t e r i l e At the beginning of the experiment pupils received an explanation about how the s t e r i l i z a t i o n process was performed. In transcripts from c l i n i c a l interviews most pupils 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 alternate views of the meaning of s t e r i l e did a l t e r pupils' perceptions -124-of the experiment. Nichola provides an example of an alternate perception of the experiment. She began the two experiments with no evidence of concepts related to the l i f e of bacteria. Her homework revealed that after experiment one she could not provide evidence that the s t e r i l i z a t i o n process was successful. In the second experiment Nichola suggested that the control plate acted as a comparison showing the difference between the plates that had bacteria on them and the plate that did not have any bacteria on i t at a l l . In the second c l i n i c a l interview Nichola suggested using a microscope to check i f tine plates were s t e r i l e . Later she suggested putting the plates i n a s t e r i l e room. Nichola claimed that anything that was s t e r i l e would stop bacteria 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 that i n some instances the agar might not be s t e r i l e so then the bacteria would grow on the agar. Nichola thought that the plates had bacteria 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 bacteria i n i t . I t i s inferred that the need for a s t e r i l e room suggests that she believes that the bacteria are continually getting i n t o the plate. I f they did and the agar was " s t e r i l e " , according to Nichola 1s meaning of the word, then the bacteria would not grow because the agar would not support growth. Nichola*s concept of s t e r i l i t y consisted of bacteria being on the plate but not growing because the agar was s t e r i l e . This i s not compatible with 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 to support the role of the control plate i n a l i m i t e d context. Nichola would think that -125-plate C was s t e r i l e as she claimed i n her interview, but she would not be able to use t h i s information to confirm that the other plates were s t e r i l e . The inadequacies of her argument perhaps are obscured because the other plates are innoculated using bacteria from pupils' hands and pupils are attempting to prevent contamination form the a i r . Nichola not only appears to have an unstable concept of s t e r i l i t y because she cannot decide i f s t e r i l e means to prevent growth (which could come from the human reproduction sense) or to 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 thinking that bacteria can get into the plates from outside. Other pupils who view bacteria seeping into the plate 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 control plate was not contaminated with bacteria after each experiment. . 5.32 Pupils' concept of growth Pupils acquire concepts from many different sources, e.g. watching t e l e v i s i o n , l i s t e n i n g to 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 to new incoming information (Freyberg and Osborne, 1981). I f these prior concepts can be used and they provide new insight into a novel s i t u a t i o n , then they could act as building blocks to further concept development. In some other instances concepts may be inappropriately linked to aspects of new information and therefore become stumbling blocks to further concept development. From analysis of the data provided by c l i n i c a l interview three, three pupils had concepts of bac t e r i a l growth but did not use them. One of -126-these pupils learned about bact 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 bacteria being plated on agar and put i n the refrigerator to grow. Since the circumstance of the class experiments were different (an incubator was used), Sharon was unable to make an appropriate l i n k with her growth concepts of bacteria present i n long term memory. Sharon's concept map possessed the most bac t e r i a l l i f e concepts compared to other pupils but some of these concepts were the re s u l t of misinterpreted information. These concepts now hindered comprehension of the experiment. Two other pupils 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 pupils who have come to the experimental setting with few previous ideas about bacteria cannot achieve an understanding of the results and purpose of the experiment. At an elementary l e v e l there are two related 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 individual c e l l s i z e or that of c e l l d i v i s i o n to increase the numbers of c e l l s i n a colony and so increase the size of the colony. I f pupils state that bacteria 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 pupil i s using. I t i s speculated that pupils who use the concept of the bacte r i a l c e l l enlarging w i l l not be able to make as much use of t h i s concept as the pupil who believes that the bacterial 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 to explain the large numbers of bacteria present i n the a i r and the potential source of bacteria from one b a c t e r i a l c e l l present i n the unst e r i l e agar. -127-I t i s speculated that pupils who do not use th e i r concept of growth i n t h e i r explanations perceive the concept of growth, related to bacteria, as an increase i n c e l l s i z e . This concept can be related to everyday l i f e , pupils observe t h e i r brothers and s i s t e r s growing withouth the notion of 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 solving Chapter Two speculated that d i f f i c u l t i e s with problem solving could be the resu l t of the lack of linkages or inadequate knowledge structures that pupils possess. Pupils are often unable to connect t h e i r constructed meaning of the problem to th e i r knowledge structures, many of the pupils interviewed for t h i s study had inadequate knowledge structures about the concept of " l i v i n g " to be able to apply these concepts to prove the success of the s t e r i l i z a t i o n procedure and explain the role of the control plate. Osborne and Wittrock (1983) observed that pupils 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, pupils chunk t h e i r sensory information, they could begin the problem by asking themselves "why does bacteria grow on a l l but one of the agar plates?" Their reasoning pattern to solve t h i s question for the f i r s t experiment, using Case's analysis, could be chunked into salient information units such as: 1) Why does bacteria grow on a l l but one of the plates? 2) I t could be that the a i r l e t into a l l but one plate had bacteria. 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-Pupils do not ask themselves t h i s f i r s t question but never the less pupils do produce the second statement i f they do not believe that bacteria are seeping into the plate. However, many pupils do not produce the t h i r d informational unit since most take for 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 pupils suggested that a microscope could be used. Pupils appreciated that bacteria were microscopic but did not appreciate that the use of the microscope would only confirm bacteria being there and not that they were l i v i n g or growing. Only a concept of growth i n terms of bac t e r i a l c e l l d i v i s i o n would generate meaning for the pupil and help explain the exponential increase of ba c t e r i a l c e l l s i n the colonies that results i n the bacteria being easily 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. This proof i s required to make information unit three s a l i e n t . Robert and P h i l i p could reason through the four information items since they had shown i n th e i r i n i t i a l interview that they had concepts of reproduction and growth that allowed them to make the information items s a l i e n t . Both reached the correct conclusion as to the role of the control plate. Steven and Nicole did not use th e i r concepts of l i f e to ra t i o n a l i z e the role of the control plate and could not reach a conclusion because th e i r concept of the sources of contamination could not support the statement made i n information item two. In th e i r view a i r may have been l e t i n t o a l l of the plates because of the "gap" between the p e t r i dish l i d and the base. In t h i s instance the perceived physical nature of the experiment may be more powerful than the concept of bac t e r i a l l i f e i n - 1 2 9 -determining the success i n providing a reason for the role of the control plate. In t h i s section we have concluded that concepts of bacte r i a l l i f e play an important role 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 pupil i d e n t i f i e s instances when the concept of growth and reproduction are relevant. I f pupils do not view the l i f e of bacteria using concepts of growth and reproduction then the whole point of the experiment becomes meaningless. In some cases alternative concepts are used i n the int e r p r e t a t i o n of the experimental data. This i s demonstrated when pupils view the bacteria i n f i l t r a t i n g the seal of the plate. For the teacher, prerequisite knowledge of the pupils* prior b e l i e f s about bacteria i s essential i n order that any effec t i v e learning be encouraged. Pupils are able to modify the i r frameworks through experimental tasks but i n many instances, t h e i r frameworks of concepts s t i l l remain inadequate i n providing meaning for the experiments. 5.4 Discussion of group work (written answers) Pupils produced answers to the questions displayed i n Appendix E for experiments one and two. These questions were intended to provide d e t a i l s of the substantive b e l i e f s held by the class about the sources of contamination, s t e r i l i z a t i o n procedure, and the role of the control plate. Analysis revealed that pupils perceived s t e r i l i z a t i o n as a means of disposing of any bacteria thay may have been on the plates prior to the -130-experiment. The s t e r i l i z a t i o n of the agar appeared to pupils to have l i t t l e relevance to the experiment since bacteria from the a i r or hands were considered as more probable contaminants. Few pupils believed that once the s t e r i l i z a t i o n procedure was complete, unintentional contamination could occur from wit h i n the plates. Some groups believed that the control plate was part of the experimental design so that pupils could compare the differences between a l l the plates while others thought that the control plate held no purpose. Another group, who believed that bacteria could seep under the p e t r i dish l i d s , thought that the control plate was designed to test i f t h i s happened. This hypothesis for the role of the control plate was more popular i n the second experiment although the f i r s t experiment could have provided evidence to the pupils that bacteria could not seep into the d i s h . Pupils attempted to generate more meaning for the second experiment by actively thinking about the reasons for 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 control plate became useful in various ways rather than having no purpose i n the experiment. These changes i n viewpoint may have been influenced by the continued inclusion 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 control plate after each experiment. Written work provided by groups i s s i m i l a r to written work provided by individuals for an exercise after the experiment. From written work the teacher can obtain a sense of the b e l i e f s held by pupils. However, as an assessable piece of work i t has l i m i t e d use. Take for 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 bacteria grow in the warm incubator. Of those seven groups only one group mentioned that apart from growing, the bacteria w i l l reproduce, or i n the pupil's term "breed". Some of the groups j u s t i f y t h e i r reasons for t h e i r answers, but from thei 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 pupils' concepts of growth. Written answers are unlikely to reveal s u f f i c i e n t information about the extent of pupils' concepts. Teachers assume that pupils know the meaning and implications of the words they use i n written work. On these assumptions teachers assess and categorize pupils as having learned or not learned the desired concepts. The written questions and answers were useful i n t h i s study as indicators that b e l i e f s revealed i n the c l i n i c a l interviews by some pupils also reflected the b e l i e f s held by other class members. However, the researcher i s not able to assess the pupils' mastery of the concept to the same extent as i n the c l i n i c a l interview. Pupils with a more comprehensive understanding of the growth of bacteria would be able to distinguish between the growth of individual bacteria and the growth of bact e r i a l colonies. This insight into pupil generated meaning i s only apparent i f one investigates the pupils' substantive b e l i e f s by using more i n depth probing measures such as interviews rather than written questions. This section reveals that s i m i l a r written assessment techniques used by teachers lack the sublety that i s required to assess pupil performance i n laboratory written work. Other methods of assessment would be more -132-useful to determine the conceptual understanding of the pupils. Section 5.7 reviews the problem of assessment of laboratory work. 5.5 Perceptions of experimental tasks The perceptions that children hold of the two experimental tasks investigated were obtained from transcripts of group work produced by twelve pupils. The analysis of the transcripts revealed that pupils did not read a l l the instructions to the experiment and instead of summarizing the procedure the groups were more content to use a recipe-following technique to 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 structure of the group influenced the perception that pupils had of the experiment. P r a c t i c a l work was seen as "assessable" by most groups and consequently the discussion of questions to 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 reinforced the pupils' attitude that answers were required to f u l f i l l the task of the lesson. Pupils' perceptions are related to the instructions of the experiment, the actions that are required and the results being observed. Consideration of these perceptions i s important when investigating pupils' experimental work since these may influence the change i n conceptual relationships within a pupil'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 discussion of thei r r e s u l t s . The boys did not read a l l the instructions. 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 pupil 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 instruction without any relationship to the others. Because the boys distributed the plates among each other, and appeared to place one pupil responsible for each plate, they l o s t sight of the o v e r a l l structure 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 in s t r u c t i o n number seven they probably read "After two days..." and thought that that piece of information was redundant at the time. In fact i t held an important concept i . e . that bacteria w i l l grow i n colonies and that after two days they w i l l be v i s i b l e to the naked eye. The lack of t h i s information meant a different perception of the results and that Steven's query, concerning i f you could see the bacteria growing immediately or not, was ignored and thought irre l e v a n t . A more subtle reason may be that i f they ignored t h i s query they could answer the question about predicted results by looking at the dust marks (produced on the plates by the wind) that they mistook for bacteria. This was f a r simpler than tr y i n g to r e f l e c t on t h e i r actions and predict an outcome. By taking a recipe-type approach to the experiment a l l pupils avoided actively generating relationships between the different aspects of the information i n the experiment. As we have seen, pupils had problems understanding that the results of the experiment would not be instantaneous. This information was available to a l l pupils i n the instructions of the experiment and could have been used by the pupils to -134-construct th e i r own information and draw inferences. The procedure of putting plates i n the incubator and waiting for two days could have confirmed t h i s information, but instead, t h i s was neither considered nor connected to 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 aid the performance of the second p r a c t i c a l task. This experience apparently did help since the pupils were not so intent on following the instructions step by step. I t was not possible to determine i f the pupils restructured the experiment to see the task according to t h e i r own framework since t h i s was not verbalized and recorded by pupils. In many cases the "discussions" about methods and results by the groups of pupils did not involve pupils i n actively l i s t e n i n g to other members of the group. Neither did i t involve testing other pupils' ideas against t h e i r own framework. There did not appear to be any attempt to construct meaning from sensed experience and concepts stored i n long term memory. I t was noticeable that i f one pupil i n the group was more respected either i n an academic or s o c i a l sense then his/her answers to questions would be approved with l i t t l e r e f l e c t i o n . The provision of an answer to questions appears to be important and pupils tend to be more answer conscious than wanting to share concepts that other pupils supply or attempting to 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 also seen as important to f i n i s h the questions even i f the answers were not as satisfactory to the group as they could have been. -135-The g i r l s exhibited the most sensitive attitude toward assessment. P r a c t i c a l l y everything that i s done i n schools tends to make pupils 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 editing t h e i r tape of any discussion 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 to f u l f i l l the task of answering the rest of the questions. The chances are that we as teachers are answer-centred and do not r e a l i z e the damage t h i s does toward the pupil's attitude of r e f l e c t i v e thought and how t h i s centring can deter groups from l i s t e n i n g to 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 pupils' frameworks - then t h i s can be found acceptable and there i s no need to suggest, r e f i n e , or l i s t e n to any other argument. The manner i n which teachers present work, plus the volume of work they assign can force pupils into these answer directed strategies. Another problem i s that i n general the pupils do not see the setting up of an experiment as work. Reflecting back on my own experience, i f you take a l l of the lesson to set up and discuss an experiment then pupils w i l l often volunteer that they did not do any work In summary, i t would appear that pupils tend to avoid r e f l e c t i n g upon the i r own physical actions, b e l i e f s and attitudes. This finding, i n combination with the pupil's attitude to p r a c t i c a l work and i t s assessment, should lead teachers to revise t h e i r presentation of experiments so that pupils become more problem centred and have an increased awareness of other pupils' viewpoints. Teachers need to present problem orientated tasks so that i n s t r u c t i o n s , actions and results can a l l be understood by generating new linkages to concepts acquired through the experiment with those already i n long term memory. -136-5.6 Conclusions This study reveals that pupils 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 bacteria. The heterogeniety of b e l i e f s i s a r e s u l t of the variety of subsuming concepts and the relationships of these subsuming concepts to each other. Prior b e l i e f s about bacteria were found to influence the way pupils 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 related to explaining colony size revealed that pupils possess different types of b e l i e f s for the concept of growth. Those pupils who constructed growth concepts primarily i n terms of an increase i n c e l l s i ze had d i f f i c u l t y i n explaining the reason for the variety of colony sizes. Those pupils whose b e l i e f s about bacteria encompassed growth concepts related to c e l l d i v i s i o n were able to explain colony growth with greater c l a r i t y . Many pupils were not able to provide more than two characteristics 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 well developed notion of growth which included c e l l d i v i s i o n or reproduction of bacteria t h i s was a s u f f i c i e n t basis for success i n interpreting the experiments. Pupils appeared to be unable to explain how to show that the equipment was s t e r i l e . Those pupils appeared to be "overloaded" with 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 dish, etc.) of the experiment. Other pupils, although possessing concepts of b a c t e r i a l l i f e , presented alternative b e l i e f s concerning the role 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 alternative b e l i e f s -137-interfered with the interpretation of the significance of the s t e r i l e equipment, medium and the significance of the control plates i n the two experiments. Pupils often thought that the control plate was to be used as a comparison between the other p e t r i dishes; a technique that could have been learnt from other science situations. The p r a c t i c a l d e t a i l s of the experiment made pupils consider using the control plate to check that no bacteria were seeping into the dishes. From 58 % of the class (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 control dish 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 pupils' reasoning to explain experiments was not simple and that t h e i r prior concepts about bacteria and those concepts acquired through the course of the experiments appear to influence the pupils' 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 variables. The l o g i c a l demands of the task were problematical to the pupils because the context i n which these demands lay were providing stumbling blocks for understanding the experiments. The suspected interference of concepts i n cognitive functions was proposed by Donaldson (1978) and t h i s study supports her view. Charles' (1976) claim that the Nuffield Combined Science curriculum can be adopted to be used successfully with nearly the whole a b i l i t y range i n secondary school can be supported i f prerequisite concepts demanded by the topic and i t s experimental work are i d e n t i f i e d and teachers assess pupils' prior b e l i e f s to detect any weakness i n these prerequisite frameworks. -138-Analysis of pupils' group work revealed i n t e r e s t i n g conclusions about pup i l attitudes to p r a c t i c a l work. Pupils 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 lay i n answering questions they thought were provided for assessment. The researcher gained l i t t l e insight into pupil reasoning concerning the procedures of the experiment or the concepts pupils possessed from the written answers to the questions since the pupils were concerned with completing the written 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 interested i n aiding pupils' learning then they need to be aware of pupils' prior concepts and how they are used i n experiments. By asking the rig h t questions teachers can help pupils to achieve meaningful learning, but i f they ask the wrong questions - those that do not encourage pupils to r e f l e c t on t h e i r reasoning - then teachers are providing pupils with meaningless p r a c t i c a l opportunities for concept acquisition. Providing opportunities for concept development would require a different emphasis on assessment and the nature of the tasks i n the classroom. 5.7 Implications of the study This section draws from the discussion and conclusions of t h i s study and discusses the implications 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 learning a c t i v i t y for pupils i s also discussed. -139-5.71 Implications for teaching  Pupils' concepts Laboratory experiments may be made more useful learning 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 that the learner must incorporate new knowledge into concepts that the learner already has" (Novak, 1980). This research has shown that pupils with inadequate concepts are unlikely to possess s u f f i c i e n t structural knowledge to incorporate new knowledge, provided by the experiment, into t h e i r framework. Teachers need to 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 pupils prior to the experiment. Pupil construction of concept maps may be a useful and less time consuming method of obtaining t h i s information than using interviewing techniques. However, from interview and mapping methods i t would be possible to ascertain i f the knowledge structures i n long term memory that may be used to generate meaning from a learning experience were inadequate or inappropriate. Tasker (1981) found that pupils' knowledge structures, against which learning experiences were considered, were frequently not those that the teacher assumed the pupil possessed. Using concept maps could provide the raw data about pupils' concepts and t h e i r relationships to other concepts and so possibly reveal t h i s mismatch between knowledge structures and learning experiences. Teaching strategies I t has been stated (Tasker, 1981) that pupils tend to consider each lesson as an isolated event and that they do not associate concepts embedded within the task as being linked with previous learning experiences. This pupil behaviour was exhibited by those pupils who did -140-not use th 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 pupil to fi n d l i n k s between knowledge i n long term memory and incoming information. I f pupils are asked to control a l l the inputs of working memory then they are dealing with 1) theory to be recalled, 2) s k i l l s to be recalled, 3) names of apparatus and materials to be recognized and associated, 4) new written instructions, 5) new s k i l l s , and 6) new verbal instructions. This i s l i k e l y to lead to an "overload" s i t u a t i o n which can re s u l t i n inef f e c t i v e learning strategies characterized by one or more of the following pupil actions: recipe-following, copying the actions of others, or busy random a c t i v i t y (Johnson and Wham, 1982). "Overload" can re s u l t i n theory applicable to the si t u a t i o n not being used. The teacher can help "chunk" incoming information for the pupil by turning the attention of the pupil toward the conceptual part of the information provided by the experiment and the methodological aspects of the experiment, prior to the experiment. Discussion along the l i n e s suggested i n Gowin's (1979) knowledge "V" organizes the thinking side of the V which i s subdivided into events, concepts, principles and theory, whereas the doing side of the V deals with objects, records, transformations and knowledge claims. The knowledge claims provide answers to the question or problem i n focus. The nature of t h i s focus question would depend on the purpose of the lesson. Pupils have been known to generate a purpose for the learning a c t i v i t y which i s very different from the teacher's intended purpose (Tasker and Osborne, 1983) so i t would be useful to e x p l i c i t l y state the -141-purpose for the experiment i n advance. Defining the purpose of the experiment i n the focus question can lead to an examination of objects and events, theory and concepts so that new knowledge i s constructed (Novak, 1980). In the present study pupils showed l i t t l e concern about the features of the investigation considered by the teacher to be c r i t i c a l design features. I t may have been helpful for the pupils to have seen, prior to 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 to be discussed i n r e l a t i o n to other l i f e concepts of bacteria and also 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 of the experiments i s the same as that of the teacher, a more sensitive method of assessment needs to be employed other than the normal answering of questions at the end of the task. I t i s suggested that the concept map provides an e f f i c i e n t method of gaining an o v e r a l l picture of the extent to which meaningful learning has taken place and i t also can be used to suggest future i n s t r u c t i o n a l needs. For example, one can look at the propositions that l i n k concepts as being indicators of the measure of d i f f e r e n t i a t i o n between constituent concepts. Nesting of concepts i s another way of demonstrating relationships between concepts and t h i s can be used as a measure of integrated r e c o n c i l i a t i o n of meanings (Cronin et a l . , 1982). Even with less sophisticated analysis the teacher can ascertain the concepts held by the pupil and gain insight into the pupil's knowledge -142-structure for a given content area. An alternative method to that of written questions for assessing pupil performance i n the classroom i s desirable since t h i s study has found that pupils are more intent on completing work that 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 individual actions which they know the teacher i s not able to assess. The pupils' 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. Pupils need to be w i l l i n g to generate meaning for 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 aid them i n the development of an understanding of the ideas of science. Teachers can motivate t h e i r pupils to do t h i s by encouraging them to become problem-centred. In order to encourage them to become problem-centred more emphasis needs to be placed on the importance of reflected thought rather than the answers to questions. For instance, the answer "bacteria w i l l grow better i n the incubator" ( t y p i c a l answer to question 7, Bacteria on Ourselves) t e l l s the reader nothing about why t h i s occurs or about the concept of growth that the pupil possesses. Knowledge, learning and understanding are not l i n e a r . I t ' s not just a matter of knowing a l l the items but of knowing how they relate to, compare with and f i t i n with each other. Written tests produced by the teacher, unless car e f u l l y devised, do not test the extent of these relationships. School work must be such that pupils' e f f o r t s i n generative learning w i l l lead to understanding. f Learning has been seen to be influenced by the learner's perceptions -143-and interpretations of the events the learner encounters. I t may be necessary that written work have focus questions to e x p l i c i t l y state objectives to c l a r i f y the intent of a lesson and that instructions encourage the pupils to consider the important design features of an experiment. Pupils' achievement can be influenced by the questions teachers ask pupils or pupils ask themselves. Group work can help pupils 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 pupils 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 written work i s demanded and, instead, pupils are encouraged to produce and present t h e i r own knowledge structures concerning the experiment. The greatest implication that t h i s study provides for teaching i s that of teachers underestimating the power of prior b e l i e f s that pupils bring to the classroom. Those pupils with adequate concepts found that af t e r experiencing the procedures of the f i r s t experiment they could carry out and interpret the intent of the second experiment with success. I f more pupils are to understand experiments then the concepts that are required for generating meaning from p r a c t i c a l work need to be assessed and i f these are found to be lacking i n pupils' frameworks then i n s t r u c t i o n a l sequences ought to be designed to take account of these alternative frameworks. 5.72 Implications for research Much useful research has been undertaken to uncover pupils' substantive b e l i e f s concerning many physical science phenomenon. Less of t h i s type of research has been involved with concepts i n the b i o l o g i c a l -144-sciences. The concepts of 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 yet do not appear to have attracted much research attention. This study has revealed that the pupils' concepts of growth and reproduction i n u n i c e l l u l a r organisms can provide useful stepping stones to generate meaning or hinder comprehension i n the two experiments studied. I t i s speculated that there are probably different b e l i e f s held concerning growth and reproduction i n simple one-celled organisms than those held i n relationship to 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 pupils to reorder t h e i r conceptual frameworks and embed them int o long term memory. When faced with a problem solving s i t u a t i o n pupils may use th e i r concepts to construct a solution. In order to do t h i s the pupil needs to understand the problem. Researchers should be asking themselves what i s the nature of the problem constructed by the pupil? I f a problem i s not constructed then i s t h i s due to sensory information not cueing aspects of long term memory and how could t h i s cueing procedure possibly work? This study begins to look at the strategies pupils employ i n order to obtain a solution to problems. I t also examines how the pupils' concepts can int 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 insight into pupils' mental a c t i v i t y and help teachers devise teaching strategies accordingly. I f p r a c t i c a l work i s not to become an interlude for pupils from other class work i n science laboratories then pupils and teachers must adopt different learning and teaching strategies. Investigations into how -145-r e f l e c t i v e discussion may improve the motivation of pupils to generate meaning from p r a c t i c a l work could provide key information as to which teaching strategies may be more useful. Research into pupil and teacher attitudes 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 assist teachers i n r e f l e c t i n g upon t h e i r own teaching strategies. This type of research has by no means come to a close and i t i s possible to look forward to further studies involving teacher and pupil 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. This can eventually lead to improved teaching strategies within the indiv i d u a l teacher's classroom that may manifest themselves i n the improvement of pupils' concepts of science. -146-REFERENCES Ausubel, D.P., The Psychology of Meaningful Verbal Learning. New York: Gruneand Stratton, 1963. Ausubel, D.P., Novak, J.D., and Manesian, H. Educational Psychology: A  Cognitive View, 2nd e d i t i o n . New York: Holt, Rinehart and Winston, 1978. Barnes, D. From Communication to Curriculum. Harmondsworth: Penguin, 1979. 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C: Well you can't r e a l l y see them unless they're under a microscope. Int.: So they are very very small? C.: Yea. Int.: Are bacteria germs? C: Well yea sort of. Int.: So what do you include as w e l l as bacteria as germs? C: I don't know r e a l l y . Int.: So you don't have a d e f i n i t e idea of what germs are? C.: No, not r e a l l y . Int.: These bacteria are they l i v i n g things? C: Yea. Int.: How do you know they are l i v i n g ? C : They've got to be haven't they. Int.: W i l l no - there are l o t s of things that are dead. C: Well i f they were dead they wouldn't be causing any i l l n e s s e s because you get different germs inside you that k i l l them so you don't get the disease. Int.: Is these a battle raging i n your body between germs? C: Could be yea i t depends. Int.: What does i t depend on? C: 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 certain disease, a very mild one. So you catch i t and then your body builds up sort of antigerms to k i l l them. . Then i f you got the disease again y o u ' l l have the antigerms there ready to k i l l them. Int.: That's good. C.: I think i t was hooping cough, measles, I can't t e l l you. Int.: That doesn't give us a good reason why bacteria are alive? C.: They produce don't they? Int.: They produce. C.: Yea. Int.: They produce what? C: Other germs. Int.: Oh, they reproduce. C: Yea reproduce that's what I meant. Int. Ok. So you would count that as a major thing of C.: And that's what Int. A l i v e . C : And what's that s t u f f i n here again...plac -160-Int.: Plaque. C : Plaque - well that produces acid doesn't i t . I f they .. when they get anything sweet that produces acid. Int.: So they are not only reproducing themselves they are producing other things., waste C.: Some do Int.: Yea waste tilings C : Yea Int.: Well why do some do that and others don't? C.: I don't know. Int.: Ok C: 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. Int.: But i f they don't take i n anything would they be alive? Don't a l l l i v i n g things need food? C.: I don't know. Int.: What could these other bacteria l i v e on i f they don't l i v e on sweet things? C : Other germs, I think inside your body. Int.: Would you only f i n d them i n your body - these bacteria? C.: Bacteria? Int.: Yes. C.: No. Int.: Where else would you f i n d them? C.: On your skin - I saw another tiling i n a magazine as well that there's about a' thousand of these l i t t l e things i n every square millimetre of your skin and i t showed up a piece of skin - a tiny piece of skin you could see them a l l over your skin. Int.: Gosh they must be very small then. C : Yea. Int.: Could they be anywhere else? C: I don't know r e a l l y . Int.: Where would we pick them up from i f they are on our skin? C.: On our skin? Int.: Yea you said there were hundreds and thousands on our skin. C.: Well I don't know where we would pick them up. We probably just get them automatically. Int.: Well you said we could use other bacteria to prevent us from getting diseases. C.: Well yes, i t ' s l i k e i n j e c t i o n s . Cause I went to Holland and I get asthma i f I go near cats because I'm a l l e r g i c to them. And I went to Holland and they had two cats and I had r e a l l y bad asthma. So I had to go back to the doctors and he said I had to go back to 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. Int.: I see. C.: I t s the same with hooping cough and that - you have injections when you're - I saw a program on that- 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 said 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 at f i v e you have a booster and you should be r i d of hooping cough. -161-Int.: You should be r i d of i t does ... C: Well i t doesn't mean that there's no chance of you getting but i t sort of means that there i s less chance of you getting i t . Int.: So that means a l l these diseases that we've been talk i n g about must be passed on somehow. C.: 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. Int.: Do you have to touch people to get these diseases? C : No, not r e a l l y , you could touch anything. Int.: So the bacteria are not only on you but on something else. C.: Yes they could be. Int.: They are on other things. C: Yes. Int.: What happens i f they are not k i l l e d ? C : They just keep well they go on and on. I'm not sure r e a l l y . Well i n the end they die. Like chicken pox you can't do anything about them except but whats i t c a l l e d again sort of plaster of paris Int.: Oh, Calamine C.: Calamine l o t i o n on them because I had that. They die o f f i n the end. I f you scratch them then they mark and they stay there for l i f e . Int.: What? C: The marks, just the marks. Int.: Are the marks the bacteria? C: Well I don't know. The bacteria cause spots. Int.: Oh they cause the spots. C.: The sort of spotty lumps. Int.: Ok. that's good. -162-APPENDIX A2 Sharon's Propositional Statements Bacteria cause disease Bacteria 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 Bacteria grow i n fridge Bacteria reproduce Bacteria are found i n food Bacteria are very small Bacteria are j e l l y l i k e , transparent Bacteria can be d i f f e r e n t shapes Bacteria may be red or white Plaque on teeth i s bacteria Can help make vaccinations to f i g h t disease Concept Map hi BACTERIA J E l u TRANSPARENT OIFFERENT SHAPES GROW IN FRIOGE COLOURS RSO. UH1TE LIVING PLAC UE which EAT OFF CEU.S REGENERATES - 1 6 3 -Neil's Propositional Statements Diseases caused by bad habits worms, tsetse f l y Colds - contagious have to give them away before i t goes. - caused by water Medicines - work by breaking down c e l l s -- aff e c t bad c e l l s - Bad c e l l s attack good c e l l s Concept Map MEDICINES break down DISEASES when BAO CELLS affect G000 CELLS caused by BAD HABITS WORMS TSETSE FLY eg becomi ng WET COLD causes COLOS are CONTAGIOUS -164-Mark's Propositional Statements Diseases are caused by d i r t germs Germs caught i n cold environments, water Cold caused by germs People spread germs Animals have germs on t h e i r bodies Germs would go into cuts Spread i n body Not big enough to see Look at them through a microscope Some germs are bigger than others Some germs are more detailed Germs l i v e i n animals and the earth Concept Map - E 2 . SOPMd 300IES -165-Justine's Propositional 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 inside people, water, a i r , food Different types of diseases caused by d i f f e r e n t types of 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" to disease Concept Map GERMS COLOS FOOD HlISOIHMl because cause COUGHS 3REATHINS PEOPLE OISEASE o t f r e t o r f TYPES IMMUNITY -166-Clive's Propositional Statements Bacteria give you diseases Bacteria are a sort of germ Different 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 Injections prevent you getting diseases Antigerms b u i l t up i n body They reproduce Plaque produces acid Germ plaque takes i n sugar Not a l l germs need food Found a l l over skin They are automatically picked up Concept Map BACTERIA LL use MICROSCOPE SORT OF GERM LIVING there are DIFFERENT TYPE! because found on SKIN automatical ly picked up BREATHING TOUCHING e cause DISEASE REPRODUCE prevented by INJECTIONS killed by ANTIGERMS and OTHER GERMS built body up in "IMMUNITY" GERM PLAQUE produce I ACID some need FOOD -167-APPENDIX B Experiment One : Bacteria i n the A i r For t h i s experiment you can work i n pairs, each member of each pair should wash his hands before the experiment. You w i l l be provided with p e t r i dishes containing s t e r i l i z e d agar. The dishes have also been s t e r i l i z e d . This means that they are absolutely clean. 1. Label the plates 1, 2, 3 and 4. 2. Choose a draughty place i n the laboratory, take o f f the l i d and expose the agar of plate 1 to the a i r for twenty minutes. 3. Choose a place i n the laboratory where there are no draughts, take o f f the l i d and expose plate 2 to the a i r for twenty minutes. You should make a draught screen for t h i s plate by surrounding i t with a ring of card-board. 4. Expose plate 3 outside for twenty minutes. 5. Do not expose plate 4 at a l l . 6. Bacteria grow best at about 37°C, so place the plates i n an incubator, at t h i s temperature. 7. After two days remove the plates from the incubator. I f bacteria have f a l l e n from the a i r onto the exposed plates they w i l l grow into colonies, and since the agar i s transparent, there i s no need to l i f t the l i d o f f the p e t r i dish to see them. Place the whole plate on a piece of black paper and the colonies w i l l show up b e a u t i f u l l y . Experiment Two : Bacteria on Ourselves For t h i s experiment you can work i n pairs. One member of each pair should not wash his 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 dish 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. Label the 3 p e t r i dishes A, B and C. 2. Plate A The person with washed hands opens A, while t h e i r partner, with unwashed hands very gently presses the fingers onto the agar j e l l y so as the not damage the surface. Replace the l i d quickly. 3. Plate B The person with washed hands opens the l i d and presses the fingers of one hand very gently on the medium and then replaces the l i d . 4. Plate C Leave unopened. 5. Put the plates i n the incubator at 37°C. 6. After two days examine the plates. -168-APPENDIX CI C l i n i c a l Interview Two "Bacteria i n the A i r " Steven The interview with Steven began by recapping the experiment. Int: What was the point of s t e r i l i z i n g the dishes and the agar before we started? S: I think that you s t e r i l i z e the dishes and then the agar because i t would stop any other bacteria getting into the agar or into the dishes. And that bacteria we don't want. We want the bacteria from a certain place. Int: OK. So are we s t e r i l i z i n g the bacteria that are already on the glass and i n the agar? S:. 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 bacteria that we don't want. Int: OK, and why did we clean our hands before? S: We cleaned our hands before we started so that, so that no bacteria would get on the glass or the agar which wasn't wanted. Int: So did we have bacteria on our hands then? S: Yes. Int: And they might get onto the agar. S: Yes. Int: Why do you think we decided to put one i n a draughty room and one i n a non draughty place? S: I f we have one i n a draughty room i t can t e l l us how much bacteria i s getting into 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 just f l o a t i n g around. Int: OK fine - and why did we leave the plates open for so long? S: Oh, i f we opened them for just 2 or 3 seconds the bacteria wouldn't have much chance to get onto i t so we had to leave them for twenty minutes so that bacteria could s e t t l e onto i t . Int: OK, so we'd have more chance of getting more bacteria then? S: Yes. Int: Now what was the purpose for having plate 4? S: Now I think the purpose for having plate 4 was so that we could see i f bacteria seeped i n through the glass, through the gaps or even through the glass onto the agar. Int: Did i t t e l l us anything about the dishes before we started the experiment? S: What do you mean by that? Int: How do we know whether the dishes were s t e r i l e before we started the experiment? S: I f you put i t i n the pressure cooker i t i s bound to get r i d of the bacteria because of the steam and the pressure. Int: How do we know i t ' s bound to? Something might have gone wrong. How would we know i f anything went wrong? S: I don't know. Int: OK. What kind of explanation can you give for these results here? S: Well, on number one i t shows that we have had a l o t of bacteria. -169-Int: This i s the one that's,outside. S: 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. Int: Do you think there are different types of bacteria i n there? S: Yes, I think that flower-one, i t looks l i k e i t i s different to that yellow smeared one. Int: Yes. OK. Why are some big and some small? S: I think i t depends on how quickly they divide or i t could be the bacteria i n the a i r and how much there i s of each. Int: OK. So there are l o t s of bacteria i n each of those colonies? S: Yes. Int: What about the differences between the draughty place, number 3 and number 2, the non draughty place? S: I think that i n the non draughty you would get more because of the, because of the um, well i t i s n ' t draughty so the bacteria just goes down, but i n 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 i n . In a draughty place i t ' s always draughty.all the time. Int: 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: What do you think the results are going to be? M: Well, I think that dish A that was the d i r t y hands would have a l o t of bacteria on i t because I've got a l o t of bacteria on my hands 'cause I haven't washed them recently. Plate B, the one with clean hands, w i l l have hardly any because he washed his hands a few minutes before he put hi s hands i n the j e l l y . Int: So you think the washing w i l l get the bacteria off? M: Yes, well some of i t , most of i t w i l l come off but some of i t w i l l stay there. Int: So that explains why some w i l l be on the j e l l y . M: Yes. Int: How about Plate C? M: Plate C I don't think w i l l have any. Int: Why don't you think i t w i l l have any? M: 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 cellotaped up and i t wasn't sealed i n so I don't think some bacteria might have been able to come i n from the a i r , but i t would s p o i l the experiment. Int: Why would i t s p o i l the experiment? M: Because we are doing i t on ourselves. Int: How could you t e l l i f the bacteria got i n from the a i r or from ourselves? M: Well, I don't know r e a l l y . There's two different kinds of bacteria, probably the one i n the a i r you know, you know i s detailed. Got l o t s of you know d i r t y marks and that, but on your hands i t probably hasn't got very much you know because you wash them. I wash them after breakfast but i f you wash them y o u ' l l s t i l l have bacteria on them, some are useful bacteria. Int: Did i t matter that the plates were s t e r i l e when we started? M: Yes, because i f they weren't clean the bacteria from the a i r and your hands would get i n there before the actual experiment because we are trying to f i n d out that bacteria are on our hands and not i n the a i r . Int: How could we t e l l i f the bacteria had got i n before the actual experiment? M: Well, you would probably see the splodges l i k e g r i t i n the dish. Int: What was the use of having plate C i f we didn't even open i t ? M: Well, to compare the answer, to compare the difference you can see whether C does have more bacteria or less than the other two. See i f plate C had less than plate B and A or more than plate B and A. Int: You said that you thought there wouldn't be any bacteria i n there. M: Well, there might be a l i t t l e b i t because i t might you know -bacteria i s f l o a t i n g about how so i t might you know come into plate -171-C. You know come up through the gaps. Int: Would that matter to the experiment? M: Well yes, r e a l l y because you're testing bacteria on yourself on your hands and i f i t came i n from the a i r then i t ' s not from yourself although i f bacteria's f l o a t i n g around now i t might get on your skin so r e a l l y bacteria from the a i r might get onto yourself you know i t ' s a guess but i t might do. Int: But i t would be important that those plates were s t e r i l e at the beginning. M: I t would otherwise i t would s p o i l the experiment because you're not testing what's i n the a i r i f you did that you're testing the bacteria on your hands Int: OK. Last question. Why do you think we put them i n a warm place? M: To keep them at body temperature because you put them i n a warm incubator at 30° at 37° and that's our body temperature. Int: So the bacteria would l i k e to l i v e at body temperature. M: Yes. Int: Fine. -172-APPENDIX D1 Class Experiment One "Bacteria i n the A i r " Group A Mark Martin Robert Steven Robert: (reads) "Choose a draughty place i n the laboratory, take o f f the l i d and expose the ..." Mark: Open the window - draughty place. Steven: Yes, there i s . Robert: I t says put the f i r s t one Mark: Plate One Robert: "Expose i t to the a i r . " Yes, plate one. Mark: "For twenty minutes". Right on your marks get set. Robert: I ' l l time i t . Steven: Look, there's a clock up there. Mark: A l r i g h t , what do we do now? Robert: Haven't you got something to put 'round i t ? Mark: No. Steven: You put both plates out don't you? Robert: No, only one. Steven: Look at the j e l l y . Mark: What do we do with the other one? Robert: Choose a place i n the laboratory where there are no draughts. Mark: "Take o f f the l i d and expose the plate 2 to the a i r for twenty minutes" - but there's no draught. "You could make a draught screen for t h i s plate by surrounding i t with a rin g of cardboard". Robert: Use the paper. Martin: I ' l l do the card. Robert: "Expose plate 3 outside". Steven: I've done that, i t ' s outside on the ledge. Robert: Right. Mark: What's th i s ? Robert: That's the question sheet, w e ' l l do that afterward, w e ' l l do t h i s f i r s t . Mark: OK, rig h t . Steven: What about the la b e l s - we l a b e l them don't we? Robert: Do we l a b e l them? Mark: We do. Robert: I ' l l l a b e l them. Mark: Plate One i s on the what s h a l l we Robert: Put plate One - I ' l l do the w r i t i n g . Mark: Plate Two. Robert: I ' l l do the w r i t i n g up of ideas. Mark: OK, you go on then put i t on number one. Robert: I t ' s outside. Steven: Does i t l i c k on? Mark: 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 testing for bacteria and we've got some j e l l y here. Mark: And on the windowsill i n the draught. Robert: We're testing the bacteria 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: I t i s . Martin: How are you going to test what bacteria's i n that one? Steven: I t ' s going to take two days. Mark: Well t h i s w i l l test i f there's bacteria i n the a i r , won't i t ? Robert: Yes. Mark: And t h i s w i l l test to see i f there's bacteria just 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 for twenty minutes outside. Steven: I t i s outside. Robert: No, that's the draughty place. Steven: Choose a draughty place i n the laboratory, 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 laboratory, 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 with 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 to go over i t with 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 said. ' 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 plate 4? Mark: Have we got a plate 4? Robert: Because i t says don't take the l i d o f f . Mark: We haven't got one anyway. Bacteria grow - after two days remove the plates from the Steven: Incubator - i t ' s got to go i n an incubator l a t e r . Mark: I f bacteria Robert: We want to do a l l our ideas now don't we? -174-Steven: Hang on, wait a minute. Robert: Number ,one, why do the p e t r i dishes, what's that oh dishes and agar absolutely clean before the experiment began? Mark: Because otherwise the bacteria w i l l be on. Robert: I ' l l write i t . What'd you put then? Mark: Answers answers at the top. Steven: Answers and then put i f you didn't wash i t clean i t f i r s t there'd be already bacteria on i t . Robert: I f the agar solution wasn't absolutely clean before the experiment Martin: S t e r i l i z e d , s t e r i l i z e d . Robert: Absolutely s t e r i l i z e d . Mark: There might be bacteria. Steven: There w i l l be bacteria, bacteria's everywhere. Mark: There would have been bacteria i n i t already. Robert: Yes. Martin: On i t . Mark: In i t . Steven: I t i s i n i t as w e l l . Mark: Now what's number two? Robert: Why did you have to have clean hands at the beginning of the experiment? Steven: Otherwise they'd have bacteria and might spread i t i n . Mark: We'd spread the disease i n wouldn't i t . Robert: Your hands were cleaned because we would have had bacteria on our hands. Mark: Three, three A. Steven: Why were dishes opened i n a draughty place. Mark: The dishes were opened i n a draughty place Robert: The dish were opened i n a draughty place (writes) Steven: To test i f there i s bacteria i n the wind Mark: In the a i r . Steven: To test for wind bacteria because look we had a draught. Robert: To test for bacteria i n the wind (writes). Mark: A draughtless place Martin: To see Mark: To test for bacteria i n calm a i r . Robert: To test for the presence (writes) Mark: For the presence? Martin: Yes. Mark: For the presence of bacteria of bacteria. What did you write for B? Robert: The dishes were placed i n a draughtless place to test for the presence i n a draughtless place. Mark: The plates were l e f t open for a long time - I think we'll have to wait for the twenty minutes before we can answer t h i s b i t . Robert: Yes - Is there a purpose for plate four - i f so, what i s i t ? We didn't have plate four but I know why. Look here, do not expose plate four at a l l . Int: Right, I'm just going to say they're a l l upstairs. I didn't give them to you because I didn't want you opening the l i d s . Mark: Yes. Int: So you've got 1, 2, 3 and there's a fourth plate s i t t i n g upstairs whose l i d s have never been taken o f f . -175-Steven: Miss, there's a plate outside. Mark: Do we answer t h i s , do we answer question four then? Int: Yes, you can answer that. Steven: Was i t because Robert: The plates were l e f t open for a long time, why was t h i s ? Uh, so that bacteria could get i n . Mark: So bacteria could get i n . Steven: Seep into the container. Robert: So that the Steven: Have you seen plate 3, i t ' s got a l l b i t s of d i r t i n i t . Robert: The plates were l e f t open for a long time because so that the bacteria could seep into the agar. Martin: To see i f bacteria could get i n . Mark: Seep i n . Martin: Through a closed Robert: Plate four was unopened to test i f bacteria could come throught the glass? Anything else? Mark: Something about i f being no bacteria? does i t change after being kept for a while? Martin: Bacteria could seep into the closed container. Steven: Yes. Robert: I f you could break into the seal. Mark: 1 Lang's just messing around. Robert: I know, and blabbing into t h i s recorder i s important. I f you could break into the sealed container can you imagine what the results w i l l be Mark: Yes, those Steven: Those exposed to the most volume. Martin: Those exposed to the most draughty place w i l l have the most bacteria because i n t h i s room there are more humans. Mark: A fast draught wouldn't have time to land on i t . Robert: Let's have a look at number three. Mark: This i s the worst one exposed to the most a i r . Robert: The one exposed to the most a i r Steven: Is that bacteria? Robert: The one exposed to the most a i r Steven: Hey look, i s that bacteria? Martin: Or the draughtiest place Robert: Of course i t ' s bacteria. I wish you'd stop showing o f f i n front of the tape recorder Steven. Steven: I'm not showing o f f . Mark: The, the Martin: The plates that are exposed to the a i r Robert: The plates that are exposed to the most a i r w i l l contain Mark: W i l l contain the most bacteria Robert: W i l l contain the most bacteria. Mark: Got two minutes to go. Robert: One minute. Mark: Shal l we turn the tape recorder off? Robert: No, leave i t on. Mark: You don't mind being turned o f f do you? We'll play i t back when we've done. Robert: Stop, bring i t i n . You can have plate one, you plate two, you plate three. Say about your plate into the tape recorder. -176-Steven: I t says you have to wait two days i n an incubator. Mark: Just say what the results are now. Robert: Here are our results now after exposing our plates to certain whizzes and a i r . Steven: On plate one we have a s w i r l 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: Plate two was -Robert: Plate two, yeh. Martin: Plate two was not exposed to the a i r . Robert: But i t was i n i t was... Mark: Plate two was not exposed to the a i r , we had Robert: We had a ring of paper round i t to keep out any draught or Steven: I t hardly got any bacteria. Robert: 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 plate three? Mark: Plate three seems to have a l o t of bacteria on i t because i t was outside on a ledge and has grains of d i r t from the wind blowing bacteria onto i t . Martin: Right, i s that i t ? Robert: Yes. -177-APPENDIX D2 Class Experiment Two "Bacteria on Ourselves" Group B Chris Andrew Michael * * u n i t e l l i g a b l e vocalizations Andy: Right, I ' l l l i f t up A and put my d i r t y hands i n . Chris: Press them i n , press 'em i n . Andy: Ow. Chris: You got to press 'em. Andy: * * do you close A? Chris: Yes. Michael: Right. Chris: Plate B, the person with washed hands opens the l i d and presses the fingers of one hand very gently on the medium and then replaces the l i d . Andy: Er, feels l i k e slime or something, er fee l s l i k e snot. Michael: Er, smells of something, er smells of disinfectant. Chris: Put that back. Michael: Plate C leave unopened. Put the plates i n an incubator. Chris: Where's an incubator? Michael: Not an incubator. Where's the incubator then? Andy: I ' l l go and ask her what to do. Chris: Go and ask Miss. Got to answer the questions now haven't we? Michael: Where's the incubator? Andy: We haven't got one. Chris: We haven't got one - questions. Andy: Won't be long. Michael: (reads) Questions. "Try and write down your ideas about the questions on the p l a s t i c overhead projector sheet". Andy: Hey (whisper) got to * * *. Chris: Come on. Andy: Ask her i f you got to record t h i s b i t ? Chris: Where's the incubator Andy? Andy: Don't know - she put them i n there I think. Michael: Try and write down yor ideas about the questions on the p l a s t i c overhead projector sheet. Your group may be asked to present t h e i r ideas to the class so think out your ideas c a r e f u l l y . I f the person handling the plates Andy: We've got to be recorded answering the questions. Chris: That's what we are doing, we are being recorded. Michael: I f the person handling Andy: Are we? Michael: The plate, what's that? Chris: During the experiment did not wash thei r hands before the experiment would i t make any difference to the result? Andy: Yes. Chris: Yes. Andy: Because -178-Michael: Number one Chris: Yes, because then both of them would be the same and you couldn't t e l l the difference. Andy: And then you couldn't compare a d i r t y hand to a clean hand. Michael: Yes, that's true. Andy: The l i v i n g organism Chris: . Then - then you can compare what? Compare the clean hand with the d i r t y hand. Michael: Oh my god, there's a frog, a frog i n there. Andy: Turner come and s i t here, I can't be near that frog. Michael: Why? Chris: To a d i r t y hand. Andy: L i f t t h i s and put your hand i n the water. Chris: Number two. Where's the frog? Michael: In that j a r . Chris: Oh, I've seen that before. Andy: Uggh, i t ' s v i l e . Michael: I t ' s v i l e . Chris: Number two, why did we have plate A unwashed hands? Andy: The person with washed hand opens i t up so that when the so that the person Michael: Oh, just farted - sorry. Andy: Got to answer t h i s . Why did 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 . A l l : (giggles and laughs) Chris: Go on, what did you say? No, keep i t on. Michael: Just 'cause you keep swearing. Andy: Right, why did we have a plate A unwashed hands? So that we can compare i t with plate B that has unwashed hands right? Michael: (giggles) Yes. Andy: Stop laughing. Michael: Stop prancing about l i k e a baby. Chris: So we can compare i t with plate B. Andy: Why did we have a plate B washed hands? Chris: So we can compare i t with plate A. Andy: So we can compare i t with plate A. Michael: Excellent. Andy: Hurry up, write i t down. Chris: (writes) Compare i t with plate A. Andy: Would you expect to see a difference i n results between the two plates, why? Chris: Yes. Andy: Yes, why? Chris: Because one w i l l have more bacteria than the other. Andy: Good answer there Chris. Glad you thought of i t . Michael: Hey look, s t i c k insects i n here as well Andy: I t ' s l i k e a zoo. (Diversion while everyone looks at s t i c k insects) Andy: Do you think bacteria w i l l grow on plate C? Michael: No. Andy: No, because ... -179-Chris: No, because i t hasn't been opened. Andy: Because i t hasn't been, well i t might have been. Chris: Yes, because the bacteria Michael: Plate C. Chris: I know, because the bacteria could be out, could get through onto the plate. Andy: No, I don't think so. Chris: No, that's no good. -Andy: Just put no. Chris: Well I think i t should. Andy: Well you're wrong. Michael: Two against one. Chris: What's number five? No, what's number six? Andy: Eh? Chris: What's question number six? Why do you think we had plate C? Andy: We just did that. Michael: Hold on, we just did that. Andy: Why do you think we had plate C? Er, to ... Chris: Because we could. Andy: To see i f bacteria could grow in plates taped up? Michael: Yes. Chris: Come on question number seven, we are on the l a s t one. Andy: Why are the plates placed i n a warm incubator? Chris: So that Andy: I t can breed. Chris: So that the bacteria can breed and grow. Andy: Switch i t o f f , we've stopped. -180-APPENDIX E Examples of Work produced from Groupwork  Experiment One : Bacteria 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 did you have to have clean hands at the beginning of the experiment? 3. Why were the dishes opened i n a) a draughty place (plate 1) b) a draughtless place (plate 2) 4. The plates were l e f t open for a long time, why was t h i s ? 5. Is there a purpose for plate 4? I f so, what was i t ? 6. Can you imagine what the results w i l l be? Answers:  Example A 1. The dishes had to absolutily clean before the experiment began so that no germs or bacteria got i n there. 2. We started the experiment, with clean hands, so that to prevent getting bacteria on the plates. 3. a) The dishes were opened i n a draughty place so that they could get bacteria from which i s carried i n the wind, b) The dishes were opened i n draughtless place so that they could get bacteria from the a i r i n a room. 4. Yes we do think that there i s a reason for plate 4 so that you can see the difference between the exposed and the non exposed. 5. We imagine that the results w i l l be a l l different because of the different place that they were i n . Example B 1. So that no germs could create on the dishes and they would be s t e r i l e . 2. We had to have clean hands because we didn't want to get germs or d i r t inside our p e t r i dishes. 3. a) The dish was opened i n a draughty place because the a i r had to get to i t . b) The dish was opened i n a draughtless place so a i r can only get i n from the top. 4. The plates we exposed for a long time were l i k e t h i s because the germs had to get into the plate. 5. Yes there i s a purpose for plate 4. No bacteria can get to i t . 6. We think the plate 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 quite 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 solution wasn't absolutely clean when the experiment began there would have been bacteria 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 to look for bacteria i n the wind, b) The dishes were opened i n a draughtless place to look for the presence of bacteria i n a draughtless place. 4. The plates were l e f t open for a long time so that bacteria could seap into the agar. 5. Plate 4 was unopened to test i f bacteria could seap into the sealed container. 6. The plates exposed to the most a i r w i l l contain the most bacteria. Experiment Two : Bacteria on Ourselves  Questions: Try and write down your ideas about the questions on the p l a s t i c overhead projector sheet. Your group may be asked to present t h e i r ideas to the class so think out your ideas c a r e f u l l y . 1. I f the person handling the plates during the experiment did not wash t h e i r hands before the experiment would i t make any difference to the result? 2. Why did we have plate A? (unwashed hands) 3. Why did we have plate B? (washed hands) 4. Would you expect to see a difference i n results between the two plates? Why? 5. Do you think bacteria w i l l grow on plate C? 6. Why do you think we had plate C? 7. Why are the plates placed i n a warm incubator? Answers:  Example D 1. Yes the plates would be diff e r e n t because we would c o l l e c t germs that we did not want. 2. We had plate A so we could see the difference between plate A and plate B. 3. We had plate B so we could see the difference between plate B and plate A. 4. Yes we would expect to see a difference between the two plates because on plate A we would expect to see germs and on plate B we would expect not to see any germs. 5. No, we wouldn't expect to see germs on plate C because i t has not been opened unless germs can get through to i t . 6. We had plate C to see i f the germs could get into the agar and to -182-see the difference. 7. The plates 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 plate A the person who didn't wash there hands put the fingers i n the j e l l y and plate B the person who did wash t h e i r hands put t h e i r fingers i n the j e l l y . 2. We had plate A for unwashed hands so that we could see how much bacteria was on your hands. 3. We had plate B so that we could compare to see i f the bacteria was s t i l l there after washing your hands. 4. Yes we would expect to see a difference because the unwashed hands had more bacteria on them and with plate B most of the bacteria was washed away. 5. We think that very l i t t l e bacteria w i l l get into 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 plate C just to see i f i t was possible for bacteria to get i n . 7. The plates were placed i n a warm incubator so that the bacteria would grow at the same rate as on our hands. Example F 1. Yes, i f the person handling the plates during the experiments did not wash t h e i r hands before the experiment when he opened the l i d bacteria would get i n from the hands. 2. We had plate A (unwashed hands) to compare with plate B (washed hands). 3. We had plate B (washed hands) to compare the difference with plate A (unwashed hands). 4. You would expect to see a difference i n results between the two plates because unwashed hands would have a l o t of bacteria but washed hands would have very l i t t l e . 5. No, bacteria w i l l not grow on plate C. 6. We had plate C to see i f bacteria could seap into the plate. 7. The plates were placed i n a warm incubator to keep them at our body temperature. -183-APPENDIX F Examples of work produced from Homework  Experiment One : Bacteria 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 did you have to have clean hands at the beginning of the experiment? 3. Why were the dishes opened i n a) a draughty place (plate 1) b) a draughtless place (plate 2) 4. The plates were l e f t open for a long time, why was this? 5. Is there a purpose for plate 4? I f so, what was i t ? 6. Can you imagine what the results w i l l be? Answers:  Nicole 1. The p e t r i dishes and agar had to be absolutely clean before the experiment began because otherwise i f any other bacteria got on i t that we didn't want we wouldn't get the results we wanted. 2. We had clean hands before the experiment because i f you didn't bacteria from your hands would get onto the dishes. 3. a) Plate 1 was opened i n a draughty place because then we could see what bacteria gets carried i n the wind, b) Plate 2 was opened i n a draughtless place because we could see what bacteria was i n the a i r around us. 4. The plates were l e f t open for a long time because we had to make sure alot of bacteria got on the plates. 5. There i s a purpose for plate 4 i t i s - : plate 4 was l e f t unopened because you can see the difference between plates 1, 2 and 3 against plate 4. 6. I imagined that the plates except plate 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 bacteria would be on the dishes already and would s p o i l the experiment. 2. We had to clean our hands, because bacteria would be on them and the agar would get bacteria on i t when we touched i t . 3. a) The dish was opened i n a draughty place to see what the bacteria i s l i k e i n the wind, b) The dish was opened i n a draughtless place to see what the bacteria i s ' l i k e i n a place with no draughts. -184-4. The plates were l e f t open for a long time because then bacteria would have a chance of s e t t l i n g i n the agar. 5. There i s a purpose for plate 4. You can compare the 3 plates exposed to a i r and plate 4 which was not exposed to a i r . 6. You can imagine what the results w i l l be. The dishes exposed to the most a i r w i l l have more bacteria than the dishes exposed to not much a i r . Robert 1. The p e t r i dishes and agar were absolutely clean before the experiment began because bacteria would be on them and they would show up i n the agar. These bacteria would be the wrong bacteria, as we were searching for bacteria 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 bacteria on them would show up on the p e t r i dishes, so sp o i l i n g the experiment. 3. a) The dishes were opened i n a draughty place to test for bacteria 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 for bacteria i n s t i l l a i r , and so that i t could be compared with dishes placed i n draughty places. 4. The plates were l e f t open for a long time so as to l e t the bacteria s e t t l e . 5. There was a purpose for plate 4. This was to see i f bacteria could seap into the sealed j a r , and so that i t could be compared with the opened dishes. This would show the presence of bacteria i n the a i r . 6. The results w i l l be that those dishes exposed to more a i r w i l l have the most bacteria on the agar. We got the res u l t s we drew because the dishes exposed to the most a i r had more bacteria on them, because more bacteria passed over and on them. Experiment Two : Bacteria on Ourselves  Questions: 1. What are the results for plates A and B? 2. Why do you think you got these results? 3. Have any bacteria grown on plate C? 4. Give a reason for your answer. 5. Are there different types of bacteria growing on plates A and B? Explain your answer. 6. What things could affect the growth of bacteria i n the dishes? 7. Did i t matter i f the plates were s t e r i l e before the experiment began? 8. How could you prove that they were either s t e r i l e or not s t e r i l e ? -185-Answers:  Nicole 1. The results for plate A and B were bacteria had grown inside the agar. They were small dots. 2. We got these results because they had germs and bacteria on them. 3. There shouldn't be bacteria on plate C. 4. No a i r has got into plate C because we never opened i t . 5. There are different types of bacteria because one person washed there hands and one person didn't. 6. Heat could affect the growth of bacteria. 7. I t did matter i f the plates 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 results from plate A and B are that B (washed hands) has less bacteria than plate A (unwashed hands) though there i s not that much difference. 2. I think I got these re s u l t s because d i r t y hands have more bacteria on them than clean hands. 3. No bacteria has grown on plate C. 4. The reason for t h i s i s because we kept the plate sealed, and so no bacteria could get i n . 5. Yes there are different types of bacteria growing on plates A and B, A has got "splodges" and big c e l l s and are on t h e i r own but B has got l o t s of l i t t l e ones stuck together. 6. A i r could affect the growth of bacteria i n the dishes. 7. Yes, i t did 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 results for plates A and B are that B, washed hands, had l e s s bacteria than A, unwashed hands, though there i s not that much difference. 2. I think we got these results because d i r t y hands have more bacteria on them, than washed hands have. 3. No bacteria have grown on plate C. 4. The reason for my answer i s that the plate was sealed, so no bacteria could get i n . 5. Yes, there are d i f f e r e n t types of bacteria growing on plates A and B, because there are dif f e r e n t types of bacteria on d i r t y hands, than there are on clean hands. 6. The things that could-affect the growth of bacteria i n the dishes are the a i r , i f there was none, so the bacteria 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 bacteria would be affected. -186-7. I t did matter i f the plates were s t e r i l e before the experiment, because unwanted bacteria would be on the dishes, so spo 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 bacteria present would grow and would be able to be seen. I f none grew then the dish would be s t e r i l e . 

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