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Examining the efficacy of using a conceptual change approach for fostering high school students’ understanding… Henry, Andrew 2005

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E X A M I N I N G THE EFFICACY OF USING A C O N C E P T U A L C H A N G E A P P R O A C H FOR FOSTERING HIGH SCHOOL STUDENTS' UNDERSTANDING OF BIOLOGICAL E V O L U T I O N by A N D R E W H E N R Y B.Sc , The University of British Columbia, 1994 B.Ed., The University of British Columbia, 1995 A THESIS SUBMITTED IN PARTIAL F U L F I L M E N T OF REQUIREMENTS FOR THE DEGREE OF MASTERS OF ARTS In F A C U L T Y OF G R A D U A T E STUDIES ("Curriculum Studies) UNIVERSITY OF BRITISH C O L U M B I A August 2005 © Andrew Henry, 2005 ABSTRACT The purpose of this study was to investigate the efficacy of a conceptual change teaching approach to an Evolutionary Biology Unit. The study was conducted in a suburb of Vancouver, British Columbia with a class of Grade 11 Biology students. The conceptual change teaching strategy was patterned after the model of Posner, Strike, Hewson, & Gertzog (1982). Student conceptions were identified through the use of two survey instruments given at the beginning and the end of the unit. The findings suggest that students enter the course with a diverse but finite range of conceptions regarding Evolutionary Biology. The findings also suggest that overall the conceptual change unit promoted students' usage of scientific conceptions. One approach that appeared successful was to make the different concepts, scientific versus alternative, explicit to students. Another approach was differentiating between the scientific and everyday meaning of terms. This study also found that alternative conceptions concerning the nature of science are very resistant to change and that teleological thinking is very compelling for students. Finally, it was found that new alternative conceptions emerge after the course which appears to be a commingling of both scientific and alternative conception. T A B L E O F C O N T E N T S ABSTRACT II LIST OF TABLES V LIST OF FIGURES VI ACKNOWLEDGEMENT VII CHAPTER ONE INTRODUCTION AND BACKGROUND 1 S T A T E M E N T O F P R O B L E M / R E S E A R C H Q U E S T I O N 2 L I M I T A T I O N S O F T H E S T U D Y 7 CHAPTER TWO LITERATURE REVIEW 11 A L T E R N A T I V E C O N C E P T I O N S , C O N C E P T U A L C H A N G E , A N D E V O L U T I O N A R Y B I O L O G Y E D U C A T I O N ..' 11 CHAPTER THREE METHODOLOGY 26 S T U D Y S I T E A N D P A R T I C I P A N T S 26 A D M I N I S T E R I N G O F T H E D I A G N O S T I C I N S T R U M E N T S 27 D E S C R I P T I O N O F T H E I N T E R V E N T I O N : A C O N C E P T U A L C H A N G E A P P R O A C H T O E V O L U T I O N IN S T R U C T I O N 28 An Example of a Conceptual Change Model Used In a Lesson 32 S U R V E Y I N S T R U M E N T D E V E L O P M E N T 33 Henry Survey 33 Bishop and Anderson Survey 34 A N A L Y S I S O F S T U D E N T R E S P O N S E S 38 1) Identifying Scientific and Alternative Conceptions 39 2) Graphing the Student Pre-Unit and Post-Unit Responses 40 3) Analysis of Students' Entering Conceptions 43 4) Analyzing Students' Post-Unit Response for Evidence of Conceptual Change 44 CHAPTER FOUR HOW EVOLUTION UNIT WAS TAUGHT 47 D E S C R I P T I O N O F B I O L O G Y 11 C O U R S E 48 U N I T P L A N A N D T I M E L I N E 49 Unit 2. Methods and Principles 53 Unit 3. Unity and Diversity- Characteristics of Living Things 53 Unit 5. Microbiology -Taxonomy & Viruses 54 Units 6. and 7. Microbiology -Kingdom Monera and Kingdom Protista 54 E V O L U T I O N C O N C E P T I O N S A D D R E S S E D IN T H E P R E - E V O L U T I O N U N I T S 55 Unit 2. Methods and Principles -The Scientific Method 55 Unit 3. Unity and Diversity-Characteristics of Living Things 57 CHAPTER FIVE RESEARCH QUESTION ONE: ANALYSIS OF STUDENTS ENTERING CONCEPTIONS TOWARDS EVOLUTIONARY BIOLOGY 59 A N A L Y S I S O F P R E - U N I T R E S P O N S E S O N T H E H E N R Y S U R V E Y 60 Conception Category 1: Conceptions about What the Theory Actually Says (Claims Made By the Theory) 63 Conception Category 2: Conceptions about the Nature of Science With Respect To Evolutionary Theory 64 Conception Category 3: Conceptions about the Legitimacy of Evolutionary Theory 65 iv Conception Category 4: Conceptions about the Relationship between Evolution and Religion.66 Conception Category 5: Conceptions about the Practical Applicability of Evolutionary Theory 67 Conception Category 6: Conceptions about the Nature of Science 68 Conception Category 7: Conceptions about the Mechanism of Evolutionary Theory (How the Theory Works -Whether Darwinian, Lamarckian, or Other) 69 A N A L Y S I S O F P R E - U N I T R E S P O N S E S O N T H E B I S H O P A N D A N D E R S O N S U R V E Y 70 Conception Category 7a: Conceptions about the Mechanism of Evolutionary Theory (How the Theory Works -Whether Darwinian, Lamarckian, or Other) 74 Conception Category 7b: Conceptions about the Mechanism of Evolutionary Theory With Respect To the Role of Mutation (The Origin of Genetic Variation) 75 Conception Category 7c: Conceptions about the Mechanism of Evolutionary Theory With Respect To the Role of the Environment (The Environment Serves to Eliminate the Unfit) 76 Conception Category 7d: Conceptions about the Usage of the Word Fitness 78 Summary of Biology 11 Students Initial Conceptions (Based On Analysis of the Bishop and Anderson Survey) 78 C H A P T E R S U M M A R Y 79 CHAPTER SIX RESEARCH QUESTION TWO: ANALYSIS OF A CONCEPTUAL CHANGE APPROACH TO TEACHING EVOLUTION ...80 D ISCUSSION O F S C I E N T I F I C C O N C E P T I O N U S E L E V E L S 1 T H R O U G H 4 83 Scientific Conception Use Level 1 -High Scientific Conception Usage 83 Scientific Conception Use Level 2 -Moderate Scientific Conception Usage 88 Scientific Conception Use Level 3 -Minimal Scientific Conception Usage 92 Scientific Conception Use Level 4 -Decrease in Scientific Conception Usage 96 N E W A L T E R N A T I V E C O N C E P T I O N S 98 Implications of New Alternative Conceptions 103 CHAPTER SEVEN SUMMARY AND CONCLUSION 105 S U M M A R Y 105 C O N C L U S I O N S F R O M R E S E A R C H Q U E S T I O N #1: 107 Conclusion Ul: : 107 Conclusion #2: : 108 C O N C L U S I O N S F R O M R E S E A R C H Q U E S T I O N #2: 109 Conclusion #1: 109 Conclusion #2: 109 Conclusion #3: 110 Conclusion #4: 112 S U R V E Y I T E M R E D E S I G N F O R T H E H E N R Y S U R V E Y 113 Change To Item #1 on the Henry Survey 115 Change to Item #12 on the Henry Survey 115 Change to Item #13 on the Henry Survey 116 A R E A S F O R F U T U R E R E S E A R C H 116 Nature of Science and Scientific Method 116 Teacher Education 117 Curriculum and Learning Resources Design 118 REFERENCES 119 APPENDIX A HENRY SURVEY 122 APPENDIX B BISHOP AND ANDERSON SURVEY 128 APPENDIX C COMPARISON OF PRE AND POST UNIT CONCEPTIONS FOR HENRY AND BISHOP AND ANDERSON SURVEY ; 131 V LIST OF TABLES Table 1 Example of Table of Data for Student Responses to Henry Survey Item 9 40 Table 2 Conception Categories 43 Table 3 Use Levels 45 Table 4 List of units taught prior to Evolution unit 49 Table 5 Unit Timeline 50 Table 6 Evolutionary Conceptions Addressed in Pre Evolution Units 55 Table 7 Conception Categories 60 Table 8 Biology 11 Students Initial Conceptions based on the Henry Pre-Survey 61 Table 9 Conception Category 7) Sub-Categories for Bishop and Anderson Items 70 Table 10 Biology 11 Students Initial Conceptions based on the Bishop and Anderson Survey 71 Table 11 Use Levels 82 Table 12 Scientific Conception Use Level 1 -High scientific conception usage 87 Table 13 Scientific Conception Use Level 2 -Moderate scientific conception usage 91 Table 14 Scientific Conception Use Level 3 -Minimal scientific conception usage 94 Table 15 Scientific Conception Use Level 4 -Decrease in of scientific conception usage 97 Table 16 New Alternative Conceptions 102 VI LIST OF F I G U R E S Figure 1. Comparison of the overall pre-unit and post-unit conceptions for the Henry Survey item number 9 42 Figure 2. Comparison of the detailed pre-unit and post-unit conceptions for the Henry Survey item number 9 42 V l l A C K N O W L E D G E M E N T I would like to sincerely thank my advisor Dr. Jolie Mayer Smith for her enthusiastic support and supervision of this thesis. Her expertise and patience during our discussions offered direction and clarity for this thesis for which I am very grateful. I express my thanks to my thesis committee members, Dr. James Gaskell and Dr. Samia Khan, for helping focus this thesis, and getting me on track to a fruitful research project from the very beginning. Thanks to the students who volunteered to participate in this study, and their parents for providing consent for their participation. I would like to thank the administration at the study school for supporting me during the research phase of this study. I would especially like to thank the Principal of the school for her consent, and her involvement in securing the student survey documents until the semester long study was over. Finally, I would like to thank my wife Denise, for her support, endless patience, encouragement, and love. To her I dedicate this thesis. 1 CHAPTER ONE INTRODUCTION AND BACKGROUND Throughout the biological sciences, the evolutionary perspective provides a framework for organizing and interpreting disparate observations, and for making predictions, about the biological world. It makes intelligible the unity and diversity of life we see around us. Evolutionary biology provides causal explanations for the history of life, as well as providing explanations for the processes of genetic change that account for this history (Dobzhansky, 1973; Evolution, Science, and Society White Paper, 2000). "Seen in the light of evolution, biology is, perhaps, intellectually the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts-some of them interesting or curious but making no meaningful picture as a whole." (Dobzhansky, 1973, p. 129) Evolutionary biology is integrated with other fields of biology, and makes societal contributions that have practical applications to our everyday lives. Molecular Biology, Developmental Biology, Physiology and Morphology, and Neurobiology and Behavior all benefit from data and approaches contributed from evolutionary biology. In the area of Human Health and Medicine, evolutionary biology has contributed to our understanding of the cause, and consequently the treatment, of genetic, systemic, and infectious diseases. Cures for medical conditions such as cystic fibrosis, coronary artery disease, and antibiotic resistant bacteria, are being found in the light of evolutionary biology (Evolution, Science, and Society White Paper, 2000). 2 In British Columbia, learning about evolution is one of the prescribed learning outcomes for Biology 11, and is one of three major themes selected for Biology 11. The intent of these themes is to "provide an organizational framework that makes studying biology simpler." (BC Ministry of Education Integrated Resource Package, 1996). The National Research Council (NRC,1996), and the American Association for the Advancement of Science (AAAS,1993), have identified evolution as a unifying concept in science education. The A A A S has specified that the concept of evolution be used to organize curriculum and guide instruction across all grade levels from K to 12. Evolutionary theory as an instructional tool provides the unifying framework for students to understand the diverse fields of biology. It is important that students get exposed to what evolutionary biology has to offer in order to prepare them for their future. According to Harvard evolutionary biologist, Stephen Palumbi (2002) "Somewhere in high school in this country is a student who's going to cure AIDS ... That student is going to have to understand evolution" (p. 50). Statement of Problem/Research Question Evolutionary theory is built on observations from the molecular to the ecological, and is a complex concept, built on other complex concepts. I have, in the past, presented evolutionary theory to my high school Biology classes only to find that students find the elements of this theory hard to grasp and difficult to utilize in their explanations for biological change. Others involved in evolutionary biology education have also found this to be the case . Researchers investigating evolutionary biology education have found that students have substantial difficulty understanding and utilizing evolutionary concepts 3 in their explanations (e.g. Bishop & Anderson, 1990; Brumby, 1984: Demastes, Good, & Peebles, 1995; Demastes, Settlage, & Good, 1995; Jenson & Findley, 1995; National Academy of Sciences, 1998; Sinatra, Southerland, McConaughy, & Demastes, 2000). Bishop and Anderson (1990) in trying to present the concept of Neo-Darwinian synthesis to college students enrolled in a non-majors in biology course, report that many of their students were not achieving an adequate understanding of the evolutionary mechanisms. Brumby (1984) in her study with medical biology students noted that although natural selection is a core concept in secondary curricula, the majority of the post-secondary medical school students in her study had only a partial or poor understanding of natural selection. These researchers, and others, have proposed an explanation for this common problem of poor understanding. The explanation proposed is that students hold what is termed "alternative conceptions" about evolutionary biology, and the theory of evolution. Clement (1982) has defined an "alternative idea" or a "misconception" in terms of three primary features. It is a conception that differs significantly from the scientific conception; it is adopted by a large portion of the population; and it is resistant to change (as cited in Fisher et al., http://naturalsciences.sdsu.edU/classes/lab2.l/altern.html). The terms alternative conception, misconception, and naive conception are used by many science educators to refer to the phenomenon in which a student has a strong commitment to an explanation or idea that is different from the scientific explanation. Alternative conception is the term preferred by many researchers as it refers to experience based explanations constructed by a learner in order to make sense of a range of natural phenomena and objects (Wandersee, Mintzes & Novak, 1994). 4 Research shows that alternative conceptions are persistent, engrained, and not readily detected by conventional testing methods. (Fisher et al., http://www.biologvlessons.sdsu.edu/philosophv/alternative.html; Wandersee, Mintzes & Novak, 1994). Alternative conceptions interfere with learning and appear to be highly resistant to change even by well-planned instruction (Brumby, 1984; Mintzes & Arnaudin, 1984; Posner, Strike, Hewson, & Gertzog, 1982). Studies show that the alternative conceptions remain intact in particular contexts. Learners who acquire scientifically acceptable viewpoints by rote, are able to apply them in school situations, but when faced with a novel situation or problem, revert to prior conceptions (Duit & Treagust, 1998; Mintzes & Arnaudin, 1984). Zietsman and Hewson (1980) claim that if these alternative conceptions can be reconciled with scientific conceptions, learning proceeds without difficulty. If these conceptions cannot be reconciled, then in order for learning to proceed, existing conceptions must be restructured or even exchanged for the new. The solution proposed to address students' alternative science conceptions comes in the form of "conceptual change instructional approaches" (Bishop & Anderson, 1990; Demastes, Settlage, & Good, 1995; Posner, Strike, Hewson, & Gertzog, 1982). It is the recognition that reconciliation or restructuring may have to occur, which forms the basis of the conceptual change model of learning and the instructional approach that emanates from this. "The term conceptual change denotes that learning of science concepts and principles usually involves major restructuring of students' already-existing preinstructional conceptions" (Duit & Treagust, 1998, p. 11). A model of learning via conceptual change was first proposed by Posner, Strike, Hewson, and Gertzog (1982). 5 According to this model there are four conditions that must be satisfied in order for conceptual change to take place. The learner must experience dissatisfaction with his/her current conception. They must then be introduction to the scientific conception that is intelligible (understandable), plausible (consistent with existing concepts), and fruitful (has explanatory/predictive power). Instructional approaches aimed to promote conceptual change begin by acknowledging that students enter courses already having developed explanations (i.e. conceptions) for many natural phenomena around them, and that in order to address any alternative conceptions, a teacher must start with what the learner already knows (Bishop & Anderson, 1990; Wandersee, Mintzes, & Novak, 1994). The goal of such instruction is not to extinguish the learner's entering conceptions, but to give the learner an awareness that, in certain contexts, science conceptions are more fruitful than their own conceptions (Duit & Treagust, 1998). Educators have worked for a number of years to develop instructional approaches aimed to help students move beyond their naive notions of scientific phenomena. These so-named "conceptual change instructional approaches" have been shown to help students increase their understanding of a topic by bridging their current conceptions with the scientific conceptions (Bishop & Anderson, 1990; Brumby, 1984; Demastes, Settlage, & Good, 1995; Posner, Strike, Hewson, & Gertzog, 1982). When Posner et al's model is adapted for classroom practice it is the teachers' role to act as the facilitator of change (Mintzes & Arnoudin, 1984). He or she creates situations in which students' alternative interpretations, or explanations for a phenomenon, are exposed and clarified. Central to this teacher-as-facilitator approach, is the timely introduction of a scientific hypothesis, or explanation. Introducing the 6 scientific "version" after the student has considered their own ideas allows the student to compare the fruitfulness of their alternative conception with the scientific conception. If the student finds the scientific conception more fruitful than their current conceptions, they will increase the usage of scientific conceptions in their explanations for natural phenomena. I've been using what I understand to be a conceptual change instructional approach for the past three years when teaching my grade 11 students their Evolutionary Biology unit. While it appears that this approach helps students utilize scientific conceptions in their explanations for evolutionary change, I have never actually documented this experience. The thesis of my study is: i f students are taught with a conceptual change instructional approach, they may increase their understanding of evolutionary biology, through increasing their usage of scientific conceptions in their explanations of evolutionary change. The study I conducted was designed to formally evaluate the efficacy of my conceptual change instructional approach in promoting student understanding of the evolutionary process. My two research questions were: 1. What is the range of conceptions held by grade 11 Canadian high school students regarding evolutionary biology, and evolutionary theory?, and 2. Can teaching an Evolutionary Biology unit, based on conceptual change instructional approaches, help students negotiate conceptual change and acquire scientific conceptions regarding evolutionary theory? This study was conducted over a three-week period. The participants in my Biology classroom were my grade 11 Biology students. I taught a unit on Evolutionary Biology and the students were given a pre-unit survey and a post-unit survey. The pre-unit survey was used to determine the students' initial conceptions of evolutionary biology. At the end of the unit, the pre-unit results were compared to the post-unit results to determine whether students increased their utilization of scientific conceptions in their explanations of biological phenomenon. This study contributes to the literature on conceptual change and evolution education. Previous studies have shown how conceptual change strategies have been successful in helping students increase their usage of scientific conceptions. Many of those same studies however, indicate that even after conceptual change instructional approaches have been implemented; there are still large numbers of students who retain their entering alternative conceptions. This study will not only provide an understanding of the range of students' conceptions of evolutionary biology, it will also provide an evaluation of an instructional approach designed to address alternative conceptions. The information and findings from this study may inform the design of curriculum and instructional materials, to increase the usage of scientific conceptions of evolutionary biology in other student populations. Limitations of the Study I used a survey approach to study my grade 11 students' conceptions of evolutionary biology before and after a unit of instruction. There are some limitations and concerns I wish to identify, which are inherent to the approach taken by this study. One limitation of the single class pre- and post-test design was the lack of a comparison group. No experimental design was possible; there were no manipulated 8 variables or trials. Another concern is that the study was conducted with a relatively small sample size of 28 students. With a population of 28 students, a change in 1 individual's response represents a change of 4%. If this 1 individual represents an extreme case, the data would be skewed. There is also the assumption that my class of students in this study is representative of Biology students in other settings. This may or may not be true. Together, these design elements limit the claims and the generalizations that can be made from this study. That the researcher was also the teacher (myself), and not someone who had no investment in the success of the conceptual change unit, presents still another limitation of the study design. Some personal bias was undoubtedly present in my class presentations, because I was trying to improve students' understanding (and use) of scientific conceptions. It would be misleading to claim that my presence was that of a completely impartial observer/researcher. My lesson plans had instructional goals, and students knew what I expected as learning outcomes. Students were aware of what I considered to be as a reasonable answer, and knew that I was looking for such answers in my evaluations. Students may have increased their use of scientific conception on some items simply because they knew what I was looking for as an answer. This study must also be tempered with recognition of limitations of using a survey approach. As with any survey based methodology, I cannot be certain how the students interpreted the items they were asked, nor can I be certain that my interpretation of their response was the one they intended. A given survey item may not elicit a student's actual conception either because the students may not have interpreted the item in the way I had intended it, or I may not have interpreted their answer in the way they intended it. 9 Thesis Organization This thesis is organized into 7 chapters. In chapter 1,1 introduce the study, I present the case for teaching evolutionary biology, and highlight alternative conceptions as one of the obstacles towards students reaching a scientific understanding of evolutionary biology. I present a conceptual change instructional approach as a technique for addressing alternative conceptions, and as a teaching strategy for helping students reach a scientific understanding of evolutionary biology. I then discuss how I have been using a conceptual change approach to teach evolutionary biology in my Biology 11 classes. In this chapter, I also present my research questions, and discuss how this study is designed to address these questions and evaluate my current conceptual change teaching approach. Chapter 2 is the literature review where I present and discuss some of the prior research that has been conducted into conceptual change approaches in the teaching of evolutionary biology. I look at findings of these researchers, and discuss how this study follows from the suggestions made by the prior researchers. In Chapter 3,1 describe the methodology used in this study. I describe the subjects, the setting of the intervention, the administration of the survey instruments (the Henry Survey, and the Bishop and Anderson Survey), and present an overview of how the teaching unit was implemented. I describe how the survey items were developed and discuss how the responses were sorted, and analyzed. 10 Chapter 4 is an explanation of how the Evolutionary Biology unit was taught. I discuss the units taught prior to the Evolutionary Biology unit, why they were introduced in the order they were, and how they were intended to support the Evolutionary Biology unit. Chapter 5 presents findings that address my first research question: What is the range of conceptions held by grade 11 Canadian high school students regarding evolutionary biology, and evolutionary theory? In this chapter I summarize the results of data analysis that pertains to this research question, and discuss these results. Chapter 6 presents findings pertaining to my second research question: Can teaching an Evolutionary Biology unit, based on conceptual change instructional approaches, help students negotiate conceptual change and acquire scientific conceptions regarding evolutionary theory? In this chapter I summarize the findings that address this research question, and offer an analysis of my findings. In this chapter I also discuss new alternative conceptions that have emerged after students had completed this Evolutionary Biology unit. My goal is to highlight these conceptions so other educators who are interested in teaching a unit of this kind are made aware of the range of alternative conceptions that may arise. Chapter 7 is the conclusion to the thesis. I begin by presenting a summary of the findings that arise from each research question separately. In this chapter I also propose changes that should be made to the Henry Survey instrument, in order to make it a more effective probe of student prior understanding. I close the chapter with a discussion of areas for future research. 11 CHAPTER TWO LITERATURE REVIEW Alternative Conceptions, Conceptual Change, And Evolutionary Biology Education Research involving evolution education suggests that there are complex interactions of prior knowledge of evolution and the nature of science that affect the learning of evolution. Demastes, Good, and Peebles (1995) identified the prior conceptions of the learner, the learner's scientific orientation, and epistemology, the learner's view of the biological world, the learner's religious orientation, and their acceptance of evolutionary theory as being influential in the process of conceptual change. Conceptions both alternative and scientific, are the learners' conceptual ecology, and shape the learning process. Research into student understanding in evolution education initially started out with studies of students' alternative conceptions of content, chiefly natural selection, but has branched into studies of alternative conceptions of the nature of science, learners epistemologies of science, and considerations of the interaction of science, and religion (Bishop & Anderson, 1990; Brumby, 1984; Demastes, Good, & Peebles, 1995; Demastes, Settlage, & Good, 1995; Jenson & Findley, 1995; National Academy of Sciences, 1998; Sinatra, Southerland, McConaughy, & Demastes, 2000). The work by Margaret Brumby (1984) was one of the first investigations to examine alternative conceptions in evolution education. She looked at one hundred and fifty first-year medical students in Australia, and investigated their understanding of the 12 topic of natural selection before and after they completed a first year lecture-based university course that dealt with evolutionary biology. In Australia, students enter medical school directly from high school. She found that the high school graduates in the medical school program had a partial or poor understanding of natural selection, even though evolution by natural selection is a core concept in the secondary school biology curricula. Students held to a Lamarckian view of evolution in which evolutionary changes appearing in organisms over time was driven by need (what is known as a teleological view) as opposed to the biological forces of genetic variation and natural selection (a non-teleological view). She referred to this form of Lamarckian reasoning as "intuitive Lamarckism". "Intuitive Lamarckism" appears to grow from an initially correct observation that individual organisms change their characteristics during their lifetime, but continues to the incorrect conclusion that these acquired characteristics can be inherited by subsequent generations. At the end of the year her subjects showed little change as a result of the lecture presentations on natural selections and genetics. A high percentage of students still held on to their entering conceptions about natural selection, with only about one third being able to express the relationship between natural selection and the frequency of genetic disease. Brumby (1984) concluded that "intuitive" reasoning needed to be explicitly identified and discussed with the student in order to assist them in shifting conceptions. Jenson and Finley (1995) undertook a study which addressed Brumby's (1984) suggestion that students "intuitive" reasoning be made explicit to them. Their study presented instruction to students which recapitulated events in the development of the Darwinian theory of evolution, and explicitly compared Lamarckian reasoning with 13 Darwinian reasoning. They used historical material as part of their strategy to affect conceptual change. They used a five step treatment. First they introduced students to the general nature of evolution and long term population change over time. Secondly they . taught students the Lamarckian explanations for change. In the third step, they presented students with evidence opposing Lamarckian principles. In the fourth step of instruction, they taught students the Darwinian theory of natural selection. The fifth step involved presenting students with an evolutionary problem and having them solve it using both the Lamarckian and the Darwinian mechanism. Through these steps, students' intuitive Lamarckian reasoning was made explicit to them, and they were challenged with discordant information by being presented with a Darwinian explanation which was more fruitful in explaining the evolutionary problems than the Lamarckian explanation. The unit of study Jenson and Finley (1995) designed was very short, 4 hours split into two 2-hour sessions, and they admit that student performance was less than optimal, but their conclusions were favorable for this type of conceptual change strategy. "It appears that i f instruction recapitulates events in the development of the Darwinian theory of evolution by natural selection in a way that meets the conditions for conceptual change, then students replace their initial conceptions with a more Darwinian conception." (p. 164) In their discussion Jenson and Findley argue for the allocation of more time for evolution instruction, and the inclusion of three specific ideas that students had difficulty learning. 1. How diversity within a population is related to the natural selection process. 2. How evolution is caused by the changing proportion of individuals within a population over several generations. 14 3. How changing environments effects the possibility of extinction or geometric growth for populations. Bishop and Anderson (1990) investigated students' conceptions of natural selection and its role in evolution, as well as students' beliefs about the theory of evolution. The main purposes of their study were: 1. To describe, as completely as possible, the conceptions held by college non science majors concerning the mechanism of natural selection and the factors responsible for evolutionary change. 2. To assess the effects of instruction (including both previous high school and college biology instruction and our college non majors' biology course) on the conceptions held by students. 3. To determine whether student conceptions of natural selection were associated with student belief in the theory of evolution as historical fact. (p. 416) Bishop and Anderson designed an instructional module for high school and college non-science majors to address students' problems associated with understanding the concepts of variation and survival in populations, and evolution. They used conceptual change strategies derived from the principles of the Posner et al. (1982) model. They also devised a diagnostic test as an assessment tool to measure student understanding following exposure to their teaching approach. The study ran for one week in a ten-week course, and was focused on Neo-Darwinism (selection acting on heritable variation, with the origin of this variation being mutation and sexual recombination). At the end of the study, Bishop and Anderson were able to identify "three major ways" in which student conceptions differed from scientific conceptions. 15 1. Origin and survival of new traits in populations: Students failed to recognize the existence of the two step process of variation plus selection. They thought that the environment alone caused traits to appear and change over time. Further, students thought that the mechanism by which the environment exerted its influence was Lamarckian, based on need, and use and disuse of parts (organs or abilities). 2. The role of variation within a population: Students did not recognize individual variation as important. They saw the environment moulding species as a whole, rather than individual members in a population possessing a reproductive advantage. 3. Evolution as the changing proportion of individuals with discrete traits: Biologists see traits increasing or decreasing in a population as discrete genetic occurrences; that is, a trait increases or decreases because the number of individuals possessing that trait increases or decreases in the population (the quantity of individuals possessing the trait changes). Students, on the other hand, attribute traits gradually increasing or decreasing in the population to gradual changes in the trait itself (the quality of the trait changes). For example, students were asked to explain how blind cave salamanders evolved from sighted ancestors. A typical response was "As sight was not needed, these salamanders in the cave, through generations, passed down genes with less ability to see until they had evolved to the blind ones" (p. 422). Bishop and Anderson (1990) also identified that students have prior conceptions that were related to terminology use. The words adapt/adaptation and fitness have 16 different meanings in evolutionary biology than they do in everyday usage. The researchers claimed it is the conception of these terms in their common meaning that prevents students from arriving at the scientific conception of the evolutionary ideas and constructs being described by these words. They argue that students must be made explicitly aware of terminology usage in evolutionary biology education. Lastly the Bishop and Anderson (1990) study looked at student belief about the truthfulness of evolution as a historical fact. They found that student beliefs on this issue were only slightly affected by instruction. That is, student acceptance of evolution as fact had little to do with the conceptual change intervention. Bishop and Anderson (1990) note that the methods they developed "were more effective than the students' previous instruction, but still left substantial numbers of students without a working knowledge of evolution by natural selection" (p 426). The results showed that previous biology instruction had little effect on students' alternative conceptions, but also, previous biology instruction did not seem to have an effect on students' ability to learn the scientific conceptions. Two key findings emerged from the Bishop and Anderson study. First, natural selection is a more difficult concept for students to grasp than previously thought. Secondly, conceptual change is possible if instructors are aware of students' alternative views and are prepared to confront them. In the Bishop and Anderson (190) study students were asked about their belief in the truthfulness of the theory of evolution, but never actually given instruction into the different uses of the word belief. There are some researchers, however, who think that simply asking students what they believe causes confusion in understanding the nature of 17 science. This is because belief has a different meaning to scientists in a scientific context than it does to lay people in everyday language. Smith (1994) holds that the researchers need to explicate for students the different meanings of the word belief before students can be asked what they believe. He explains that when scientists use the word belief they are referring to something well grounded in evidence. They are conveying their degree of acceptance of a concept. In lay usage however, belief is often interchangeable with faith. One believes not because of the evidence, but in spite of any evidence to the contrary. The lay person hearing the phrase "believe in evolution" may construe a very different meaning than the scientist. They may construe a meaning that implies personal faith with no evidentiary basis. Because of the potential for misunderstanding, it is nonsensical to ask a student to "believe in evolution". According to Smith (1994), there is however a place for instruction on the word "believe" in evolution education. That place is in pointing out the different meanings of the word to students so that they can see the two different ontological categories behind the word (i.e. the physical/science category, and the metaphysical/faith category), and become aware of the possible confusions involved in using the word. Smith (1994) claimed: .. .drawing carefully the distinction between belief (or faith) in the absence of objective evidence and acceptance that is based on evidence provides an excellent opportunity for helping students understand what science is. (p. 595). By allowing students to see that the term belief as applied to science differs from belief as applied to issues of faith, students can more accurately see what scientists mean 18 when they use the word believe in the context of their work. This can possibly help students avoid the confusion of conflating belief based on faith (in the absence of objective evidence) with belief based on science (predicated on the acceptance of objective evidence). Demastes, Settlage, and Good (1995) expanded on the work of Bishop and Anderson (1990) by doing a dual study with two study groups. In one study they replicated the work of Bishop and Anderson "in order to investigate the generalizability of the results" of the Bishop and Anderson study. They used the same conceptual change instructional materials and the same testing instruction with a similar sample of university students. For comparison purposes they conducted a second study with another group of students. Their subjects for the second study were high school students, and the teaching materials and approach were based around an inquiry approach. Demastes, Settlage, et al. wanted to define the limits of the original Bishop and Anderson work as well as "propose avenues for further studies". Both studies they conducted used the same Bishop and Anderson diagnostic test. Demastes, Settlage, et al's (1995) study with university students ran for one week, and the researchers found only a "meager increase" in students' use of scientific conceptions about evolution, as compared to the Bishop and Anderson (1990) results. They determined that the reason for this meager increase was that the teachers involved in the study were unfamiliar with the conceptual change teaching approach of Bishop and Anderson. They suggested that in order for conceptual change to occur, the teacher must be versed in the conceptual change model, and the instructional philosophies inherent to it. According to Demastes, Settlage, et al., teachers must be able to identify alternative 19 conceptions, and present comparisons to these alternative conceptions, in order to help students negotiate conceptual change. Demastes, Settlage, et al's (1995) study with the high school students extended over a six week period. In their study the students were found to show "significant increases" in utilization of scientific conceptions post-test. The researchers claimed the level of success in this study was related to the fact that the instruction had conceptual change strategies built into the inquiry approach model. There was opportunity for students to interact with the teacher and with peers, and many lessons utilized hands-on activities. They also noted that the time difference involved in the two studies may have played a role in the different results, and agreed with Jensen and Finley (1995) that time is a potentially limiting factor in conceptual change. The students in the six week study may have had time to construct better understanding during instruction. In their discussion, Demastes, Settlage, et al. (1995) identify that negotiating conceptual change is not just important for the students in understanding evolution, but that instructors must also undergo a conceptual change in terms of their epistemologies and pedagogical approaches to science teaching. They call for more instructional time for teaching evolution, and for further research into the role of teachers' theories of learning, and their impact on students' success in achieving conceptual change. The work of Bishop and Anderson (1990), Brumby (1984), Demastes, Settlage, et al. (1995), and Jenson and Findley (1995) focus on alternative conceptions of natural selection, or Neo-Darwinism (natural selection working on heritable variation). However, although natural selection is the adaptive mechanism in evolutionary change, there are more factors associated with evolutionary change, and hence more conceptions 20 of evolution than just those associated with natural selection. Beyond conceptions of adaptive mechanisms of evolution, there are also conceptions about the nature of science, and the relationship of science and religion with respect to evolutionary biology. The National Academy of Sciences (1998) acknowledges many of the alternative conceptions that surround evolution education and attempts to address them in their publication Teaching About Evolution And The Nature Of Science. This document explores the supporting evidence for evolution, and offers clear definitions of science and science-related terms such as theory, law, fact, and inference. These are terms that have alternative (layman) conceptions that are completely different from the scientific conceptions. The document discusses legal and educational issues and offers an explanation for the position of science with respect to religious issues. One source of resistance to the teaching of evolution is the belief that evolution conflicts with religious principles. But accepting evolution as an accurate description of the history of life on earth does not mean rejecting religion. On the contrary, most religious communities do not hold that the concept of evolution is at odds with their descriptions of creation and human origins. (Preface section, If 8) This publication anticipates common alternative conceptions, about evolution and the nature of science, and provides ideas, answers, and strategies for addressing these alternative conceptions in the context of an evolutionary biology unit. The authors go further though, by providing specific strategies to teach about the nature of science. They provide an activity based on teaching the nature of theory formulation which takes a "black box" approach. The students are given a six sided cube with different patterns on 21 each side, and they have to figure out what is on the bottom of the cube by following, and extrapolating from, the pattern on the exposed five sides. They cannot lift the cube. The (intended) thought process students go through is analogous to the approach taken by researchers where they make observations of the natural world, and try to infer a pattern; they then make predictions of future outcomes based on that pattern. The cubes range in difficulty from a simple number pattern, to a cube where students must figure out the name of an individual, down to gender, and spelling. Since students never see the bottom of the cube, they will never be 100% sure about the spelling. They can never prove they are right, the best they can do is disprove (rule out) the other options that they might generate, that do not fit the pattern they observed. Students are forced to make a decision in a climate of uncertainty, and must justify why they chose the pattern and number they did. This activity is intended to reveal how scientists make tentative decisions in uncertain conditions, decisions that are subject to change and revision when new knowledge comes along. The activity is also designed to assist in changing students' conceptions of scientific knowledge as static, and to show the explanatory power and the tentativeness of a theory. It is also designed to show that the acquisition of scientific knowledge is a human endeavor subject to human error and opinion. Nature of science instruction has been pointed out by other researchers as an effective way to increase student's acceptance of evolutionary biology because this type of instruction allows students to see the fundamental assumptions and scope of science (Sinatra, Southerland, McConaughy, & Demastes, 2000). Sinatra et al., (2000) studied the effect of students' intentions and beliefs on their acceptance of biological evolution. They note that epistemological beliefs influence 22 whether students accept the concept human evolution. They argue that the learner actively chooses to consider alternative points of view, rather than the learner being controlled solely by external factors (content presented during instruction). The more sophisticated the learner's epistemological view of the nature of science, the greater the likelihood that the learner would accept evolutionary theory. By sophisticated, the researchers mean that the learner understands the fundamental assumptions of science, its methodologies, limitations and boundaries. If the student sees knowledge and theory as uncertain and changing, then they will be disposed toward open-minded thinking. They argue that sophisticated epistemologies with respect to the nature of science, foster evolution acceptance and conclude that educators should integrate nature of science instruction into evolution education. Together these studies illustrate that there is potential to increase students understanding of evolutionary biology by including instruction in nature of science concepts alongside of instruction in evolutionary theory. The majority of studies I found that investigated evolution education and conceptual change researched only alternative conceptions about Neo-Darwinian mechanisms. These studies were not only Neo-Darwinian-centric, but were also of short duration. A number of researchers called for a longer time frame to carry out studies of evolution education (Demastes, Good, & Peebles, 1995; Demastes, Settlage, & Good, 1995; Jenson & Findley, 1995). Based on these studies and my own experience teaching high school Biology, I think there is a need to extend instructional time to evolution education beyond a few hours or even one week. I also think there is a need to extend the scope of research on alternative conceptions beyond neo Darwinian mechanisms to the whole of (or at least more of) evolutionary education. 23 Evolution involves more than natural selection. There is change at or below the population level, there is change above the population level resulting in speciation (reproductive isolation), and there is common descent and historical narrative. Even though natural selection is the mechanism of directional change at the population level, there are more mechanisms of change at this level; and even though natural selection can lead towards speciation, it is not in itself an isolating mechanism. I think evolutionary theory presented in a coherent manner makes connections from D N A and population genetics, up to speciation and change above species level. It makes connections with the fossil record and the concept of common descent, and addresses the nature of science and scientific thinking. It allows students to use the theories of evolution to make their own predictions, and offer their own explanations about the world in which they live. A curriculum that extends beyond neo Darwinian explanations however will face alternative conceptions that too extend beyond neo Darwinian explanations. In order to equip educators to address the alternative conceptions that may arise, I think that research needs to be done on courses designed to present this extended evolutionary picture to students. I have tried to present to my students a coherent complete, picture of evolution that moves from genetic mechanisms to speciation to common descent, and incorporates nature of science concepts. In presenting my lessons I have found that alternative conceptions regarding many aspects of evolution arise regularly. I have been trying to address these alternative conceptions by using a conceptual change teaching approach. I have, with this research project, decided to formally investigate my Evolutionary Biology unit to see i f my students' alternative conceptions are actually being addressed by my conceptual change method of teaching. . 24 Over the years of teaching grade 11 Biology, I have encountered, and made note of, students' alternative conceptions about evolution that go beyond the neo Darwinian mechanism. I compiled these into a survey that I administered to the students along with the Bishop and Anderson diagnostic test. These conceptions pertain to the nature of science, the definitions of theory and law, whether evolutionary theory is acceptable to religious organizations, the difference between evolution of life and origin of life, and the practical utility of evolutionary theory. My research focuses on a broad range of student conceptions about evolution. To answer the research questions in my study I identify students' alternative conceptions, and attempt to promote conceptual change towards scientific conceptions through administering a teaching unit on evolution over a three week time period. I draw upon some aspects of previous research conducted on evolution education in this study, and extend the work of these researchers. Following the work of Brumby (1984) and Jensen and Finley (1995), I introduce a teaching unit where I directly compare Lamarckian mechanisms of evolution with Darwinian mechanisms. Students are given an explanation of both principles, and challenged to explain observations of nature using these principles. Following Smith's (1994) suggestion, I explore the different meanings of the word belief with my students in order to illustrate that differences exist, and to help students avoid the category confusions that may get in the way of their understanding of the conduct of scientific endeavor. Similar to Bishop and Anderson (1990), my study does not involve a comparison group, and student conceptions of evolutionary biology are analyzed pre and post 25 instruction using the Bishop and Anderson diagnostic test. Students' entering conceptions are made explicit through the pre-unit survey, during the unit of study, they are presented with scientific conceptions of natural selection acting on variation, and at the end of the unit they complete a post-unit survey for comparison of their entering and leaving conceptions. Unlike Bishop and Anderson's work however, my study extended over three weeks instead of just one addressing both Jensen and Finley (1995), and Demastes, Settlage, et al. (1995) calls for allocating more instructional time to evolution education. The extended time frame allowed for more in-depth coverage of the material than done by Bishop and Anderson, and permitted me to satisfy all the learning outcomes of the BC curriculum (outcomes not addressed by Bishop and Anderson). Also, as suggested by Demastes, Settlage, et al., my study involved an instructor (myself) who was familiar with conceptual change literature, methods, and instructional philosophies. Similar to the work of Bishop and Anderson, Brumby (1984), Demastes, Settlage, et al., and Jenson and Findley, my study deals with Neo-Darwinian evolution (selection acting on variation). However, unlike the previous researchers, my study also looks at other factors related to evolutionary change, to determine if there are alternative conceptions besides those associated with Neo-Darwinian principles. In the next chapter I present the methodology I use for my study. I describe the site location, the participants, and the survey instruments used. I outline the instructional approach used in the intervention itself, and explain how the responses to the survey items were analyzed. 26 C H A P T E R T H R E E M E T H O D O L O G Y This study was designed to investigate the efficacy of a conceptual change evolutionary biology unit. In this chapter I present information about how this study was conducted. I begin by describing the site location and the participants involved in this study. I then explain how the diagnostic survey instruments were administered in order to gather the data. I move on to a description of the intervention where I describe the instructional approach used for this teaching unit, and present an overview of the actual course as taught. I then explain how the surveys were developed, and describe any changes that were made to the instruments as implemented in this study. I close the chapter with a discussion of how the student responses were analyzed in order to answer my two research questions: 1. What is the range of conceptions held by grade 11 Canadian high school students regarding evolutionary biology, and evolutionary theory? 2. Can teaching an evolutionary biology unit, based on conceptual change instructional approaches, help students negotiate conceptual change and acquire scientific conceptions regarding evolutionary theory? Study Site and Participants This study was conducted in Upper Middle Secondary School (a pseudonym) in British Columbia Canada. Upper Middle Secondary School is located in a suburban area in the southern BC lower mainland and offers courses from grade 8 to grade 12. The 27 Majority of students come from upper middle class professional families. The student body represents a cultural mix that is largely European Canadian. The second largest cultural group represented is Indo Canadian. The third largest group of students is the Asian Canadian population. Upper Middle Secondary is highly academic, with a large number of the grade 12 graduating class destined for post secondary education. The school is semestered having a Fall intake running from September to January, and a Spring intake running from February to June. It offers academic courses leading to grade 12 graduation, as outlined by the BC Ministry of Education, as well as a number of locally developed district programs. The participants in the study were the students enrolled in my Biology 11 class who obtained parental consent to be in the study. Twenty nine consent forms were returned out of a class of thirty students. However, the data set included only twenty eight students as one student's responses were illegible, and not used in the analysis. Administering of the Diagnostic Instruments Students' understanding of the evolutionary biology concepts was surveyed by the use of two different diagnostic survey instruments. One survey, designated the "Henry Survey", consisted of 14 short answer items. I designed these open-ended items to reveal students conceptions about different aspects of evolutionary biology. The second survey instrument used was the Bishop and Anderson (1986) Diagnostic Test for Student Understanding of Natural Selection. The instruments will be described in detail later in this chapter in the section titled "Survey Instrument Development". 28 Both surveys were administered before the three-week unit on Evolution was taught, and then again at the end of this three week unit of instruction. A l l students enrolled in my Biology 11 class completed the two surveys as part of their regular involvement in this teaching unit. But only those students who agreed to participate, and obtained parental or legal guardian consent, had their data considered for inclusion in the analysis portions of this study. A l l analyses of the survey data for this study took place after the semester long course had ended. The diagnostic instruments were used for two purposes. First they were used to find out what types of conceptions students hold prior to receiving instruction in the evolution unit. The second purpose of the surveys was to provide a means of judging the extent of students' conceptual change following the unit of instruction. The data analysis involved comparing students' responses on the pre-unit surveys with responses on the post-unit surveys to determine if the students' conceptions changed, and in what direction, and to what degree. Description of the Intervention: A Conceptual change Approach to Evolution Instruction The guiding methodology driving the conceptual change unit I taught on evolution is based on ideas emanating from the theory of constructivism. According to this theory, learning is not simply a transfer of knowledge, but is a case of the learner actively constructing, his or her knowledge on the basis of their own prior knowledge (Duit & Treagust, 1998). Prior knowledge however comes with prior conceptions, conceptions that may or may not match the current understandings in science. Given this 29 as my starting point, the goal of my Evolution unit was to address the prior conceptions that come with this prior knowledge, by teaching my unit using a conceptual change teaching approach. In what follows I describe the procedures I followed for the teaching of my unit on evolution. I adopted a "social constructivist" framework for my unit on evolution. In this framework, knowledge is viewed as distributed among the members of a community. Knowledge is constructed in a social setting where knowledge is negotiated, and ideas compete for dominance. Learning situations are dominated by open inquiry where knowledge is something that is shared between the individual and the community (Duit & Treagust 1998). I arranged the students in groups of 4, and encouraged and expected them to discuss and negotiate their assignments, as they worked towards answers and solutions. I started the unit on evolution by having students complete the two pre-unit survey instruments. These surveys are intended to reveal to students their entering conceptions about certain evolutionary concepts. Throughout the unit, as the lessons proceeded, we encountered the concepts that were examined in the surveys. As each topic came up I introduced students to the scientific views regarding those topics, following the model of conceptual change proposed by Posner et al (1982). I first introduced students to the topic of the age of the earth, and then used the geological timeline to point out when certain events occurred on the earth. I used this investigation of the timeline to differentiate between evolution of life and origin of life. I then introduced students to the concept of evolution based on the evidence for common descent. I presented students with direct and indirect evidence for evolution, and students work through a case study on the evolution of the horse. 30 Next I presented the concept of evolution through a present day population genetics point of view. From a genetics point of view, change in gene frequency (genotype) leads to change in appearance (phenotype), which is evolutionary change. I introduce the theories that explain the mechanisms of evolution (mutation, migration, genetic drift, and natural selection), and have students investigate how these mechanisms can change allele frequencies, and thus cause evolutionary change. These mechanisms of evolutionary change are intelligible i f students first understand Mendelian genetics and D N A replication, so I had students work through a review of Science 10 genetics before the concept of population genetics is introduced. Students throughout this unit were given opportunities to reason through the material in order that they would construct their own meaning. Questions on population genetics are posed for students. The student has to figure out whether population change has occurred, and if change has taken place what type of mechanism is at work. They do this by solving population genetics calculations to determine if in fact an evolutionary change had occurred. After we looked at the mechanisms that cause evolutionary change, I presented students with a more in-depth study of Darwin's Theory of Natural Selection. I highlighted natural selection as the one mechanism known to causes adaptive (directional) change; and present natural selection in a historical perspective, subsequent to a presentation of Lamarckian theory. After being presented with both Lamarckian and Darwinian mechanisms students were asked to compare the two explanations put forth by the two theories to determine which mechanism more successfully explains observations of evolutionary change. By asking students to make this comparison I hoped they would 31 see that natural selection may be a more fruitful explanation for adaptive change than the Lamarckian explanation I presented to them first. I then introduced students to scientific definition of a number of terms such as theory, law, and hypothesis, in order to distinguish between the scientific and the common everyday usage of these words. I assigned a poster project in the final week of the unit. This poster project was designed to get students to research and present one practical application of knowledge about Evolutionary Biology. For the poster, students were asked to complete four tasks. Students were to: 1) describe a particular application; 2) describe who is using the application (in what field of science it is used); 3) explain how knowledge of evolutionary biology is being used to inform this field of science; and 4) describe the future outlook for this application (future jobs, medicines, future technologies). Students worked in groups of four on the poster for three days in class, and submitted their finished product the following week. 32 An Example of a Conceptual Change Model Used In a Lesson Alternative Conception being addressed Alternative Conception #2 from the Henry Survey: According to the theory of evolution, all organisms are constantly evolving. Scientific Conception being presented In a freely interbreeding population, allele frequencies are expected to remain the same generation after generation. It is only when certain factors (mutation, migration, genetic drift, non random mating, selection) cause allele frequencies to change that a population evolves The 4 Steps of Conceptual Change Following the Posner et al. Model 1. I Create dissatisfaction with existing conceptions by posing the question. • If organisms are constantly evolving, how do biologists explain organisms that show no evolutionary change over large periods of time (ex cockroaches, horseshoe crabs, mosses, ferns)? • Also, how do breeders keep Chihuahuas from reverting back to ancestral types? 2. I present a new conception that is intelligible. • Students have worked with the Hardy Weinberg equation, and can determine the frequencies of alleles in a population for one generation. • To make the new conception intelligible, students must extend their knowledge to calculate allele frequencies for subsequent generations, to see that the frequencies remain the same. 33 3. I present a new conception that is plausible. • This concept is consistent with students' past experience and other theories of knowledge. • Population genetics springs from an understanding of Mendelian genetics, (which students have studied in grade 10 and reviewed here). • The idea that populations remain stable generation after generation, because allele frequencies remain stable generation after generation is plausible. 4. I present a new conception that is fruitful. • The new conception explains why populations don't change, but when considered along with the factors that do cause change in allele frequencies (mutation, migration, selection, genetic drift, non random mating), it explains why populations do change as well. Survey Instrument Development Henry Survey This survey instrument emerged from my experiences of teaching evolution. Over the years I have found that students hold a number of alternative conceptions about evolution. To create my survey I compiled the conceptions that emerged regularly, and turned these conceptions into probe items. The probe items were intended to reveal students' conceptions, scientific or alternative. The scientific conceptions used for probe items on the survey were taken from the science textbooks used by the school district, university reference textbooks, and research studies conducted on evolution. 34 Bishop and Anderson Survey As mentioned in previous chapters, Bishop and Anderson (1990) used a questionnaire as a survey instrument in their research on Students Conceptions of Natural Selection and It's Role in Evolution. The actual survey however, was developed by them years earlier (Bishop & Anderson 1986) for use in a teaching module designed to address the major conceptual problems involved in evolution education. The module was titled Evolution by Natural Selection: A Teaching Module. For my study I used most, but not all items, found on their original survey instrument. I changed the wording in part of item 3 from "Biologists believe that ducks evolved from land birds which did not have webbed feet." to "Biologists explain that ducks evolved from land birds which did not have webbed feet." I also changed the wording on a portion of item 4 from "Biologists believe that DDT resistance evolved in mosquitos because: (choose the best answer)." to "Biologists would explain that DDT resistance evolved in mosquitos because: (choose the best answer)." I made these changes because I did not want students to respond as if they were agreeing or disagreeing with what someone else believed. I did not want them to interpret the item as an opportunity to give personal opinion, free of rationale. I wanted students to respond as if they were agreeing or disagreeing with the current state of understanding in evolutionary biology. By replacing the term "believe" with the term "explain", I hoped to achieve that goal. I also removed item 6 "Do you believe the theory of evolution to be truthful? Why or why not?" I made these changes because I think that Bishop and Anderson's use of the word belief (in their survey) is confusing and misleading. The researchers use the term belief in different ways depending on the item. On one hand they use the term, belief to mean 35 general acceptance of a concept or idea. For example, when they ask students about DDT resistance in mosquitos, their item reads, "Biologists believe that DDT resistance evolved in mosquitos because?" Later in their survey they use belief to mean a philosophical commitment to a concept or idea. For example, they ask the students i f they ^believe the theory of evolution to be truthful? Why or why not?" These two uses of the term belief are not clarified for students in the Bishop and Anderson teaching module (1986), resulting in what I think is a confusion over what type of ontological category that evolution falls into. That is, does belief in evolution involve a general acceptance of the concept of evolution or does belief in evolution a philosophical commitment? Students may not know or understand what the concept of "belief in evolution" means. This is because scientists and the lay public use the word belief in different ways. When scientists use the word belief they are referring to acceptance of a concept based on evidence. In contrast, the lay person's use of the term belief often refers to a belief in a concept that is based on faith in the absence of objective evidence (Smith, 1994). Close inspection of the Bishop and Anderson (1990) study shows some of, what I think are, the problems associated with their undifferentiated use of the term belief. Regarding their survey item that asked: "Do you believe the theory of evolution to be truthful?" Bishop and Anderson found that 59% of the respondents were "believers", and 11% were "non-believers" before the course, but at the end of the course, 49% were "believers", and 26% were "non-believers". Over the course of their study the number of "believers" decreased and the number of students responding as "non-believers" increased. Rather than try to investigate why students' conception of evolution as being 36 truthful diminished after the course, however, Bishop and Anderson offer these comments while discussing implications. "The results do not indicate, however, that better understanding of scientific accounts of the process of evolutionary change would lead to a general acceptance of evolution as a historical fact... This may be disturbing to biologists who would like for the general public to believe and appreciate the discipline's central theory, but it should be comforting to those who fear that instruction in evolution will cause students to abandon religious beliefs." (p. 426) I think they miss an important question. Why would students' belief in the truthfulness of evolution decrease if their evolution unit was successful? I think that the number of non-believers may have increased because of the nature of the item asked. The concept of belief juxtaposed with the concept of truth, presented students with a philosophical dilemma. Evolution when presented in this context, is no longer an explanation of the physical world, it becomes a truth claim about the origin of humans, one that students are asked if they believe. This item forces students to make an ontological shift away from thinking about evolution as a physical explanation, and towards considering evolution as a metaphysical belief. According to a Gallup poll done in 1999, many people hold a metaphysical belief about the origin of humans. Forty seven percent of people surveyed believe that God created human beings pretty much in their present form at one time within the last 10,000 years or so (as cited in Wikipedia, http://www.wikipedia.org/wiki/Evolution_Poll). Thus, what the Bishop and Anderson item did was put evolution on par with religion as a metaphysical belief. It was then left up to the student to decide which metaphysical belief they wished to accept, one that they 37 may have learned in previous years, and have been accepting all their lives, or one they heard about in their science classroom. The process of evolution is not a truth claim; it is a physical process. Science provides explanations for natural phenomenon, and does not prevent, nor explain the actions of supernatural creators working in supernatural ways. Most students are i l l equipped to handle an item that mixes views related to faith with scientific beliefs supported by evidence. To reduce the possibility for this type of confusion, I removed this problematic item from the Bishop and Anderson Survey, and asked a similar but differently phrased item on the Henry Survey. I wanted to find out if students think evolutionary theory is legitimate science without forcing evolution into an ontologically religious category by asking students what they "believe". I also wanted to explicitly juxtapose explanations based on evolutionary discourse with explanations based on religious discourse so that students had to consider both at the same time, when trying to arrive at their answer. Thus I framed my item in three parts. I asked students to what degree they think explanations for the origin of humans are science or religion. That is, I wanted to know if they think that while they are explaining the origin of humans, they are engaging in a scientific discourse or a religious discourse. I then ask them if they think evolution offers an explanation for the origin of humans. Finally I ask them if they think evolution is science or religion. If students think the concept of evolution is part of, or related to religious discourse, they hold the conception that evolution is a metaphysical belief. If they think evolution is a science concept, this suggests they do not hold the conception that 38 evolution is a metaphysical belief. If students view evolution as a metaphysical concept, then they may regard this concept as competing with other long held metaphysical views (religion). If however, students see evolution as part of scientific rather than religious discourse, they may not perceive a tension between evolutionary theory and religious belief, and be better able to reconcile explanations borne from evolutionary discourse with explanations borne from religious discourse. I also ask whether evolution is incompatible with religion. I think this point, and not a belief in truthfulness of evolution, is key to understanding i f students accept or reject evolution as an explanation for how organisms change over time. If students think that evolution is in conflict with their religious views, then they will have to make a choice between the two. If however, they don't see evolution as being in conflict with religion, they will not have to make such a choice. If they can accept both, there is no need to believe in the truthfulness of evolution (as asked by the Bishop and Anderson survey). Analysis of Student Responses Analysis of the student responses involved four procedures: 1) sorting the student responses for each survey item into categories of scientific and alternative conceptions, 2) graphing by item the numbers of student scientific and alternative responses in each category, 3) analyzing the pre-unit responses to answer the first research question, 4) comparing the student pre-unit and post-unit responses to determine i f use of scientific conceptions increased after students participated in a conceptual change unit on evolutionary biology, to answer the second research question. 39 1) Identifying Scientific and Alternative Conceptions Student pre-unit and post-unit responses were sorted item-by-item and analyzed for the presence of scientific and alternative conceptions. For each item, student responses were read and grouped with responses that appeared to present similar answers. Through this process the sets of responses representing students' scientific and alternative conceptions emerged. If for a given item there was more than one type of conception emerging from the analysis of responses, the conceptions were numbered. For example, if an item elicited three different alternative conceptions, the alternative conceptions would be numbered from one to three (the numbering order was sequential but arbitrary). A l l responses were recorded in tables by item, and organized into scientific vs. alternative conceptions. The tables indicated the frequency for given response in the pre- and post-data set. Table 1 provides an example of how responses to survey item 9 from the Henry Survey were scored and recorded. The complete set of data tables and graphs for all surveys is included in Appendix C. 40 Table 1 Example of Table of Data for Student Responses to Henry Survey Item 9 Item #9 Henry Survey: The theory of evolution is not testable, because the only way to do that would be to go back into time and actually watch the animals as they change, and there is no way you can do that. Type of Response Frequency of Responses Pre-Unit Post-Unit Survey Survey Scientific Conception #1 2 1 Evolution can be tested by collecting data today, and having future generations analyze that collected data. Scientific Conception #2 1 0 Evolution can be tested; the technology (techniques) is available now for us to do that. Scientific Conception #3 9 13 Evolution can be tested by reconstructing past changes through historical evidence (ex the fossil record). Scientific Conception #4 2 8 Evolution can be tested by causing organisms to evolve (microevolution) Alternative Conception #1 14 6 Evolution is not testable because we don't have the ability to actually watch the postulated historical changes (We would need a time machine to test evolution). 2) Graphing the Student Pre-Unit and Post-Unit Responses Student responses to survey items were converted to percentages and represented in graphical format. Two types of bar graphs were produced, one bar graph was a comparison of the overall pre and post totals for scientific and alternative conceptions. The other provided a more detailed graph illustrating the range and frequency of individual conceptions. 41 An example of the first type of graph is shown in Figure 1. This figure presents the data for survey item 9 from the Henry Survey. The pre-unit total percentages were calculated for scientific conceptions and alternative conceptions and represent the student's initial conceptions prior to their receiving instruction in this unit. Taking the graph in Figure 1 as an example, 50% of the students entered the course holding the scientific conception that evolution could be tested. The other 50% held the alternative conception that evolution could not be tested. An example of the second type of graph is shown in Figure 2. 42 SC Evolution can be tested. AC Evolution cannot be tested. Figure 1. Comparison of the overall pre-unit and post-unit conceptions for the Henry Survey item number 9. 60% 50% 40% 30% 20% 10% 4 0% ' 7% 4% 46% 1321 0% '• 50% 21%. B Pre Unit Totals • Post Unit Totals SC1 Evolution can be SC2 Evolution can be SC3 Evolution can be SC4 Evolution can be AC1 Evolution cannot tested by collecting tested, the technology tested by tested by causing be tested because we data today to analyze in exists for us to do that. reconstructing past organisms to evolve don't have the ability to the distant future. changes though fossils. (microevolution). watch the postulated changes. Figure 2. Comparison of the detailed pre-unit and post-unit conceptions for the Henry Survey item number 9. 42 SC Evolution can be tested. AC Evolution cannot be tested. Pre Unit Totals Post Unit Totals Figure 1. Comparison of the overall pre-unit and post-unit conceptions for the Henry Survey item number 9. 60% 50% 40% 30% 20% i 10% 0% SC1 Evolution can be S C 2 Evolution can be S C 3 Evolution can be SC4 Evolution can be A C 1 Evolution cannot tested by collecting tested, the technology tested by tested by causing be tested because we data today to analyze in exists for us to do that. reconstructing past organisms to evolve don't have the ability to the distant future. changes though fossils. (microevolution). watch the postulated changes. Figure 2. Comparison of the detailed pre-unit and post-unit conceptions for the Henry Survey item number 9. 43 3) Analysis of Students' Entering Conceptions After the student responses were organized into scientific and alternative conceptions, and the results graphed, I grouped the survey items that dealt with related topics into similar categories, which I refer to as Conception Categories. I identified seven Conception Categories shown in Table 2. Table 2 Conception Categories Conception Categories Dealing with Conceptions About: Survey Items 1. What the theory actually says (claims made by the theory). 1,2,3 (Henry Survey). 2. The nature of science with respect to evolutionary theory. 4, 5c, 7, 9 (Henry Survey). 3. The legitimacy of evolutionary theory. 6 (Henry Survey). 4. The relationship between evolution and religion. 8 (Henry Survey). 5. The practical applicability of evolutionary theory. 11, 12 (Henry Survey). 6. The nature of science. 13 (Henry Survey). 7. The mechanism of evolutionary theory (what explanations are used -whether Darwinian, Lamarckian, or other). 14 (Henry Survey). 1 to 5 (Bishop and Anderson Survey). I analyzed responses for items in each conception category to identify students' scientific and alternative conceptions that related to each category. The Henry Survey items covered the entire range of Conception Categories from 1-7. The Bishop and Anderson items pertained to Category 7 only. In chapter five I use the seven Conception Categories as an organization template to answer my first research question "What is the range of conceptions held by grade 11 Canadian high school students regarding evolutionary biology, and evolutionary theory?" 44 I analyze and discuss student responses beginning with Conception Category 1 and proceeding through to Conception Category 7. 4) Analyzing Students' Post-Unit Response for Evidence of Conceptual Change To answer research question 2, " Can this unit help students acquire scientific conceptions?" I looked at two criteria, 1) whether the degree of change of students use of scientific conceptions in their survey responses appears large or small (in relative terms), and 2) if the number of students that use scientific conceptions in their explanations post the teaching of the evolution unit increased. If the increase in usage of scientific conceptions was large (i.e. greater than 50%) and the majority of students use scientific conceptions after the unit, I took that as indication that the teaching process was successful in supporting conceptual change and that conceptual change was easy to "facilitate". Conversely i f a smaller increase was evident (i.e. less than 50%) then I assumed that I was less successful with my conceptual change approach and/or the given alternative conception was more resistant to change. Using these two criteria as a guide, I looked at the graphs of the comparison of pre-unit and post-unit conception data (found in appendix C) for each survey item, to determine what increases or decreases in usage of scientific conception occurred for these items (an example of the pre-unit and post-unit conception data is represented in Figures 1 and 2 in this chapter). I then established four scientific conception categories, which I refer to as Use Levels, based on the degree of usage of scientific conception from pre- to 45 post-unit. Items showing similar usage patterns were clustered and assigned the appropriate scientific conception Use Levels (refer to Table 3). Table 3 Use Levels Scientif ic Concept ion Use Levels Survey Items 1. Level 1: High scientific conception 1, 8, 9, 12, 14 (Henry Survey). usage. The usage of the scientific 1, 2, 3d (Bishop and Anderson Survey), conception increased; and the scientific conception was used by the majority of the students (>50%). 2. Level 2: Moderate scientific conception usage. The usage of the scientific conception increased, and the scientific conception was used by <50% of the students. 3. Level 3: Minimal scientific conception 3b, 3c, 5 (Bishop and Anderson Survey), usage. The usage of the scientific conception increased minimally (<10%), and the scientific conception was used by <50% of the students. 4. Level 4: Decrease in scientific 13 (Henry Survey). conception usage. Items designated as Use Level 1 represent survey items which I categorized as showing a high scientific conception usage post-unit. For these items the usage of the scientific conception increased, and the scientific conception was used by the majority of the students (scientific conception used by >50%). Items designated as Use Level 2 represented a moderate use of scientific conception, where the scientific conception increased and was used by <50% of the students. Items designated Use Level 3 represented a minimal scientific conception usage, where the usage of the scientific conception showed only a very slight increase (<10%), and the conception was used by <50% of the students (note 10% represents 2-3 students). Items designated Use Level 4 represented a decrease in scientific conception usage. In Table 3, the Scientific 2, 3, 4, 7 (Henry Survey). 3a, 4, (Bishop and Anderson Survey). 46 Conception Use levels are listed in the column on the left, and the Survey Items that satisfy the criteria for a particular use level are listed in the column on the right. In Chapter five, I analyze the student survey responses based on the organization of data (graphs and tables) discussed in this chapter to determine students' conceptions prior to participating in the Evolution Unit. In Chapter six I use the organization of data presented in this chapter to compare students' pre-unit to the post-unit survey responses to determine whether the course was successful in increasing students' usage of scientific conceptions of evolutionary biology. 47 CHAPTER FOUR HOW EVOLUTION UNIT WAS TAUGHT This chapter is devoted to explaining how the unit on Biological Evolution was taught. Fundamental to the design and teaching of this unit is the assumption that student learning involves conceptual change and that such change can be advanced via a social constructivist approach. This study also views conceptual change as going hand-in-hand with constructivist approaches. The model for conceptual change used in designing the Evolution unit was derived from Posner et al. (1982). According to Posner et al., in order for conceptual change to be achieved, the learner must experience dissatisfaction with his or her initial conception. This dissatisfaction must be addressed through the presentation of the scientific conception in a way that the learner will find it intelligible, initially plausible, and ultimately fruitful. In what follows, I outline the instructional approaches taken throughout this unit. I begin with a brief description of the structure and organization of the Biology 11 course in British Columbia. I then present the unit timeline which gives an overview of each of the lessons taught. I then move on to a discussion of the units covered prior to the Evolution unit. In my discussion I explain why I chose to put these units before the unit on Evolution, and why I chose to put the Evolution unit where I did in the course. Finally I look at conceptions of evolution I address in the pre-Evolution units, and explain how these units were used to support the conceptual change anticipated to occur in the Evolution unit. 48 Description of Biology 11 Course Biology 11 is a survey course based on the five Kingdom system of taxonomic classification. It is structured around three major themes; Unity and Diversity, Evolution, and Ecological Relationships. The curriculum is typically organized to follow a taxonomic sequence from a molecular to an ecosystem level of organization (BC Ministry of Education Integrated Resource Package, 1996). Before starting the unit on Evolutionary Biology, I teach units on Methods and Principles of Biology, Unity and Diversity, Ecological Relationships, and Microbiology. Table 4 lists the order in which units are taught. This order is followed to provide a logical sequence to the course, as well as to give students some background knowledge upon which they may construct their understanding about Evolutionary Biology. It is worth noting that not all the units taught prior to the Evolution unit were geared to providing background knowledge for evolution. For example, Unit 1 on Course Start Up was simply a start up unit where we do house keeping, course introduction and class expectations, textbook distribution and damage reports, and lab safety. Unit 4 on Ecological Relationships was time-tabled to correspond with scheduled field trips and guest speakers. 49 Table 4 List of units taught prior to Evolution unit. 1. Course Start Up 2. Methods and Principles -The Scientific Method. 3. Unity and Diversity- Characteristics of Living Things -Cell Structure -DNA replication, Protein Synthesis and Amino Acids -Origin of the First Cell 4. Ecological Relationships-Biochemistry & Ecosystems 5. Microbiology -Taxonomy & Viruses 6. Microbiology -Kingdom Monera 7. Microbiology -Kingdom Protista 8. Unity and Diversity-Evolution 9. Ecological Relationships -Plant Biology & Mycology 10. Ecological Relationships -Animal Biology 11. Ecological Relationships -Ecology Unit Plan and Timeline In Table 5,1 present a timeline of the unit I teach on Evolutionary Biology. The unit is based on a 15 day, 3 week timeline, with the classes being 75 minutes long. The alternative conceptions being addressed are those identified from the survey instruments given at the beginning of the course (and again at the end). In the Table, HS stands for Henry Survey, and BAS stands for Bishop and Anderson Survey. Item numbers are indicated in parenthesis and correspond to the numbers of the items on the surveys. For example, on the first day of the course (Day 1) I address an alternative conception that is discussed in item number 3 on the Henry Survey. In the table, Day 1 contains the corresponding reference (HS. 3). For details of the survey items, refer to Appendices A and B, the Henry Survey, and the Bishop and Anderson Survey respectively. Table 5 Unit Timeline Day 1 Day 2 Day 3 Day 4 Day 5 Topic/Aim: Topic/Aim: Topic/Aim: Topic/Aim: Topic/Aim: -Pre instructional surveys and -Geological time -What are -Who agrees with the -Define biological evolution. -Mendelian genetics, a quizzes. the factors that contributed to teaching of evolution in -What is a fossil and how are they review from Science 10. -Geological time -How old is evolution of life on Earth? schools? formed? the Earth? -What's the difference -How do they provide direct Students Will Be Able To: between evolution of live and Students Will Be Able evidence for evolution? -Define the following terms Students Will Be Able To: origin of life? To: and give an example of -Illustrate the age of the Earth. -Identify organizations Students Will Be Able To: each. (Refer to Ch. 5 p. 140 -Identify the different time Students Will Be Able To: that support the -Define evolution - 146 Nelson Biology). periods in the history of the -Illustrate the age of the Earth. teaching of evolution in -Explain how the fossil record Gene, Allele, Dominant Earth. -Identify the different time schools. provides direct evidence for descent allele, Recessive allele, -Describe factors that have periods in the history of the -Identify that religious with modification. Genotype, Phenotype, contributed to evolution of life Earth. organizations support -Describe how fossils are formed. Homozygous, Heterozygous on Earth -Describe factors that have the teaching of -Differentiate between absolute and -Describe how genotype -Differentiate between origin of contributed to evolution of life evolution. relative dating. leads to phenotype life and evolution of life. on Earth -Explain why it's difficult to observe -Using Punnet squares, -Identify the role of extinction -Differentiate between origin Activities: large scale evolutionary change solve problems based on in evolution of life and evolution of life. -Voices for Evolution. occurring in present day time frames. simple Mendelian crosses -Identify the role of extinction Internet research on (Parent, Fl & F2) Activities: in evolution organizations that Activities: -Pre Instructional Quiz support the teaching of -Observe Whale evolution sequence. Activities: -Geological timeline project Activities: evolution. -Case Study: Evolution of the Horse. -Review and reinforcement -Geological timeline project of grade 10 genetics terms Alternative Conceptions Alternative Alternative Conceptions and concepts. Addressed: Alternative Conceptions Conceptions Addressed: -The theory of biological Addressed: Addressed: -The theory of evolution has some Alternative Conceptions evolution is used to explain the -The theory of biological -Evolution is holes in it. If organisms were Addressed: origin of life. (HS. 3) evolution is used to explain incompatible with evolving, you would still be able to -None. the origin of life. (HS. 3) religion. (HS. 8) see them evolving today, and you don't. (HS. 6) 50 Table 5 (continued) Day 6 Topic/Aim: -What are the indirect lines of evidence for evolution? Students Will Be Able To: -Describe the indirect lines of evidence that support evolutionary theory. -Differentiate between homologous and analogous structures -Use examples to distinguish between convergent and divergent evolution (ex humans and monkeys = divergent evolution, shark and dolphin skin texture=convergent). -Explain why it's difficult to observe large scale evolutionary change occurring in present day time frames. Activities: -Textbook book research summarizing indirect evidence for evolution. Alternative Conceptions Addressed: -According to the theory of evolution, humans evolved from monkeys. (HS. 1) -The theory of evolution has some holes in it. If organisms were evolving, you would still be able to see them evolving today, and you don't. (HS. 6) Day 7 Topic/Aim: -Population Genetics, the Hardy Weinberg Principle Students Will Be Able To: -Describe the frequencies of alleles in a population in Hardy Weinberg terms. Ex A+a = 1 is expressed as p+q = 1 -Determine the frequencies of alleles in a population using Hardy Weinberg notation. p+q=l -Determine the frequencies of genotypes or phenotypes in a population using Hardy Weinberg notation. p2+2pq +q2=l Activities: -Hardy Weinberg case study. Alternative Conceptions Addressed: -None. Day 8 Topic/Aim: -What is the genetic basis of evolution? -How do we use Hardy Weinberg to calculate genotypic and allelic frequencies in a population? Students Will Be Able To: -Explain why in a freely interbreeding population, the gene pool will have the same composition generation after generation. -Generate a Hardy Weinberg equation from observed phenotypes. -Use the Hardy Weinberg equation to calculate genotypic and allelic frequencies in a population. Activities: -Practice problems generating Hardy-Weinberg equations. Alternative Conceptions Addressed: -None. Day 9 Topic/Aim: -How can we calculate whether a population has evolved or not? -What are the factors that cause evolutionary change? Students Will Be Able To: -Describe evolution in genetic terms, as a change in allele frequency within a gene pool. -Calculate whether a population has evolved or not using the Hardy-Weinberg equation. -Suggest conditions under which the allelic frequencies of a population could change, including, genetic drift, differential migration, mutation, and natural selection. Activities: -Calculate allele frequency changes over time (evolution) -Textbook research on 4 (of 5) agents of evoln. Cage Alternative Conceptions Addressed: -The theory of evolution has some holes in it. If organisms were evolving, you would still be able to see them evolving today, and you don't. (HS. 6) -The theory of evolution is not testable, because the only way to do that would be to go back into time and actually watch the animals as they change, and there is no way you can do that. (HS. 9) Day 10 Topic/Aim: -What is the Theory of Natural Selection? -How does the Theory of Natural Selection provide better explanations than the theory that came before it (Lamarcks theory of Inheritance of Acquired Characteristics)? Students Will Be Able To: -Describe the process of natural selection -Compare and contrast the theories of Darwin (Natural Selection) and Lamarck (Inheritance of Acquired Characteristics) Activities: -Comparison table Lamarck v. Darwin. -Problem sets (multiple choice) Lamarck v. Darwin. Alternative Conceptions Addressed: - A l l Bishop and Anderson diagnostic items. (BAS. 1-5) -The fossil record shows that the ancestors of giraffes did not have long necks. Formulate an explanation for how you think giraffes got their long necks, (i.e. Change is Lamarckian) (HS.14) 51 Table 5 (continued) Day 11 Topic/Aim: -Modeling Natural Selection. -How does evolution affect my life? Students Will Be Able To: -Model natural selection. -Observe the role of the environment in determining the direction of selection. -Identify real life applications for evolutionary biology. Activities: -Activity: Natural Selection Model -Poster Project: Practical Applications of Evolution (Day 1 in class) Alternative Conceptions Addressed: -All Bishop and Anderson diagnostic items. (BAS. 1-5) -Bacteria are evolving resistance to antibiotics (i.e. evoln. has no practical applications). (HS. 11) -Evolutionary theory is used to cure cancer (i.e. evoln. Has no practical applications). (HS. ) Day 12 Topic/Aim: -Science Terminology and Word Usage -Types of selection -Case study, the peppered moth. - Vocab. theory, law, hypothesis, belief -Three types of selection in, directional, stabilizing, disruptive. - Case Study: Adaptation and the Peppered Moth. Students Will Be Able To: -Use science terminology such as theory, law, in their correct scientific context. -Identify the three different types of selection. -Explain how stabilizing selection prevents evolutionary change. -Describe the peppered moth study as real life example of evolution in action via natural selection. Activities: -Compare science terminology usage, within science and without. -Case Study: Adaptation and the Peppered Moth. Alternative Conceptions Addressed: -According to the theory of evolution, all organisms are constantly evolving. (HS. 2) -Evolution is a belief held by some scientists but not by all. (HS. 4) -Evolution is a religious belief. (HS. 5) -If evolution were true it would be a law not just a theory. (HS. 7) Day 13 Topic/Aim: -What is the source of the variation that the environment selects from? -What is the role of sexual reproduction in variation and evolution? -How does evolution affect my life? Students Will Be Able To: -Explain the role of sexual reproduction in variation and evolution. -Describe with examples, a practical application of evolutionary biology. Activities: -Poster Project: Practical applications of evolutionary biology.(Day 2 in computer room) Alternative Conceptions Addressed: -Bacteria are evolving resistance to antibiotics (i.e. evoln. has no practical applications). (HS. 11) -Evolutionary theory is used to cure cancer (i.e. evoln. has no practical applications). (HS. 12) Day 14 Topic/Aim: -How do new species form? -Is evolution always a gradual process? Students Will Be Able To: -Describe the process of allotropic speciation. -Compare and contrast the gradual change model with the punctuated equilibrium model of evolution Activities: -Solve practice problems: Speciation, geog. & repro. isolation -Solve practice problems: Rates of evoln, gradual vs. punctuated equilibrium -Review For test next week Alternative Conceptions Addressed: -Small populations evolve faster than large populations because in small populations it's easier to lose genes. (HS. 10) Day 15 Topic/Aim: - How does evolution affect my life? -Post instructional surveys and quizzes. Students Will Be Able To: -Describe practical applications of evolutionary biology Activities: -Study Guide (take home review package) -Poster Project: (Day 3 in computer room) last day in class, project due next week. -Post instructional surveys and quizzes Alternative Conceptions Addressed: -Bacteria are evolving resistance to antibiotics (i.e. evoln. has no practical applications). (HS. 11) -Evolutionary theory is used to cure cancer (i.e. evoln. has no practical applications). (HS. 12) 52 53 What follows is a brief rationale for the sequences of pre-Evolution units I present in Table 4. I summarize the background knowledge students are expected to have as a result of these units, prior to beginning the Evolution unit. Unit 2. Methods and Principles During the Methods and Principles unit, students are taught about the scientific method and the concept of science as a black box where known inputs provide expected outputs which allow one to form inferences about the mechanisms which produced the outputs. Students should learn how to formulate a hypothesis, and how a theory is derived. They are introduced to science terminology and should learn the differences between the concepts of hypothesis, law, and theory, as these ideas apply to science generally. Unit 3. Unity and Diversity- Characteristics of Living Things In Unit 3,1 teach the topics of Cell Structure, D N A replication, Protein Synthesis and Amino Acids, and Origin of the First Cell. This unit teaches students the characteristics of living things, the impossibility of spontaneous generation, and current explanations for the origin of the first living things. Students are introduced to simple cell structure and function, and at the end of the unit they should be able to recognize cell organelles, and should understand that the nucleus is the location of D N A in eukaryotic cells. At the end of this unit I expect that students know that D N A codes for protein (via RNA), and that proteins get constructed from amino acids. They should have learned that 54 proteins control phenotype, and that mutation in D N A can ultimately result in changes in phenotype. In the unit they are exposed to the process of gel electrophoresis, and through a case study Amino Acids and Evolution (Ritter, Coombs, & Drysdale, 1996) they learn how amino acid sequences are analyzed, to determine the degree of relatedness in fly species. I also introduce students to phylogenetic trees built on protein sequence information, and through the Amino Acids and Evolution case study mentioned previously, teach students that phylogenies show ancestral relationships. Unit 5. Microbiology -Taxonomy & Viruses In Unit 5,1 introduce students to one of the common classification systems used to organize living things, the Linnaean Five Kingdom System. By the end of the unit I expect that they know how to create and use a classification system, specifically a dichotomous key, that they understand the importance of classification in biology, and that they know that there is more than one system for classifying organisms. I also expect that they are aware that biological classifications show relatedness in organisms. Students study the bacteriophage as a representative virus, and look at virus structure and infection cycle. They study the concept of flu outbreaks, and should be able to describe how different viral strains mutate through antigenic drift and shift. Units 6. and 7. Microbiology -Kingdom Monera and Kingdom Protista Students learn about the two Kingdoms that contain single celled organisms in the Five Kingdom System, Monera, and Protista. I teach students the concept of antibiotic 55 resistance at the genetic level and how mutations are responsible for creating antibiotic resistant bacteria. Evolution Conceptions Addressed In the Pre-Evolution Units. Unit 2 on Methods and Principles, and Unit 3 on Unity and Diversity directly address some of the alternative conceptions germane to the evolution unit. The pre-Evolution units and the related conceptions are presented in Table 6. The numbers that are shown in parenthesis following the conception statement indicates the number that this statement corresponds to on the Henry Survey. Table 6 Evolutionary Conceptions Addressed in Pre Evolution Units Unit Conception Unit 2. Methods and Principles -The word disproof is more valid in science -The Scientific Method. than proof. (HS 13) Unit 3. Unity and Diversity -If organisms were evolving, you would - Characteristics of Living Things still be able to see them evolving today, but -Cell Structure you don 7. (HS 6) -DNA replication, Protein Synthesis -Evolution is not testable. (HS 9) and Amino Acids -Origin of the First Cell Below is a short discussion of the intended learning outcomes for both units, and an explanation of how the unit addressed the alternative conceptions. Unit 2. Methods and Principles -The Scientific Method. In Unit 2 there are five student learning outcomes. The learning outcomes are formulated in the form of the statement Students Wil l Be Able To: (SWBAT). 56 (SWBAT) 1) Define theory, law, hypothesis. 2) Explain how a theory is formulated through the metaphor of a black box. 3) Describe how scientists make decisions based on limited information. 4) Explain why theories can never be proven, but they can be disproved. 5) Formulate and test simple if/then hypotheses. To address these five learning outcomes students participate in two activities. The first activity takes a black box approach. The students are given a six sided cube with different patterns on each side, and they have to figure out what is on the bottom of the cube by following, and extrapolating from, the pattern on the exposed 5 sides, without lifting the cube. The activity is taken from the publication Teaching About Evolution And The Nature Of Science (National Academy of Sciences, 1998). Since they never see the bottom of the cube, they will never be 100% sure about the pattern. They can never prove they are right, the best they can do is disprove the other options that do not fit the pattern they observed. In the second activity, students are given two clear liquids which turn blue upon shaking, then go back to clear when allowed to settle. They have to formulate and test a hypothesis about whether these two liquids are the same or not. Through the students formulating and testing their hypotheses, they see again, that they can never be 100% certain. The closest they get to proving they are "right" is in determining if they can accept their hypothesis. Through this unit I am trying to introduce the conception that the term disproof is more valid in science than the term proof. I try to get across the idea that in science, scientific theories are intended to offer explanations that are subject to change. 57 They offer no absolutes, such as final proof. Theories simply give the best explanation we have right now. Scientists formulate hypotheses and seek to disprove them through testing. If a hypothesis is disproved, it is rejected. If it is not disproved, it is accepted, and the explanation gained from the hypothesis is added to those which further strengthen the theory. Unit 3. Unity and Diversity -Characteristics of Living Things In Unit 3 there are three student learning outcomes. (SWBAT) 1) Explain how gene mutations cause changes in protein sequences. 2) Describe the process of gel electrophoresis 3) Test common descent hypotheses using protein sequence data. Students were introduced to protein synthesis and the effects of mutation on protein synthesis, so that they can understand the genetic mechanism behind phenotypic change. Students then work through the case study titled Amino Acids and Evolution (Ritter et al., 1996). In the case study, students are given a page of amino acid sequences from three different insect species in order to test the hypothesis that living things that are morphologically similar share similar protein structure. This is a test of the common descent hypothesis. This activity introduces the scientific conception that it is not necessary to see organism evolving in order to formulate tests to see i f evolutionary change is occurring, or has occurred. Evolution, as common descent, can by tested by hypotheses such as in the case study above. The activity is intended to address two alternative conceptions regarding evolution. First, that the theory of evolution has some 58 "holes" in it, because i f organisms were evolving, you would still be able to see them evolving today, and you don't (HS. 6). Second, that the theory of evolution is not testable, because the only way to do that would be to go back into time and actually watch the animals as they change, and there is no way you can do that (HS. 9). Up until Unit 7 topics are presented as discrete concepts and I do not formally present a way to tie these discrete concepts together. I then teach Unit 8 on Evolution as per the Unit Timeline shown in Table 5. In this unit evolutionary biology serves as an explanatory tool that is intended to help students make connections between the disparate concepts they have previously studied, and allow them to make sense of the similarities and differences that exist in the biological world. In the next chapter I answer my first research question: What is the range of conceptions held by my group of grade 11 Canadian high school biology students regarding Evolutionary Biology, and Evolutionary Theory? I analyze student responses to items on the Henry and the Bishop and Anderson Surveys to identify the range of students' pre-instructional scientific and alternative conceptions related to each survey item. 59 CHAPTER FIVE RESEARCH QUESTION ONE: ANALYSIS OF STUDENTS ENTERING CONCEPTIONS TOWARDS EVOLUTIONARY BIOLOGY This chapter addresses the first research question: What is the range of conceptions held by my group of grade 11 Canadian high school biology students regarding Evolutionary Biology, and Evolutionary Theory? I summarize the results of my research related to this question, and offer an analysis of the results. Prior to my teaching of the Evolution Unit I had my student's complete two survey instruments, the Henry Survey and the Bishop and Anderson Survey. For analysis purposed, survey items that dealt with related topics in evolution were grouped together. These groupings or "Conception Categories" are shown in Table 7. I analyzed responses for items in each conception category to identify students' scientific and alternative conceptions that related to each category. A l l of the Bishop and Anderson Survey items pertain to Conception Category 7 (Conceptions about the mechanism of evolutionary theory). However, as the Bishop and Anderson survey instrument focuses specifically on students' conceptions of Natural Selection as an evolutionary process, I discuss the Bishop and Anderson Survey responses separately from the Henry Survey responses. The outcome of my analysis for Items in the Henry Survey is shown in Table 8 page 61, and discussed by conception category in the next section of this chapter. This is followed by my analysis of student responses to the Bishop and Anderson Survey. The outcome of that analysis appears in Table 10 on page 71. 60 Table 7 Conception Categories Conception Categories Dealing with Conceptions About: Survey Items 1. What the theory actually says (claims made by the theory). 1, 2, 3 (Henry Survey). 2. The nature of science with respect to evolutionary theory. 4, 5c, 7, 9 (Henry Survey). 3. The legitimacy of evolutionary theory. 6 (Henry Survey). 4. The relationship between evolution and religion. 8 (Henry Survey). 5. The practical applicability of evolutionary theory. 11, 12 (Henry Survey). 6. The nature of science. 13 (Henry Survey). 7. The mechanism of evolutionary theory (what explanations are used -whether Darwinian, Lamarckian, or other). 14 (Henry Survey). 1 to 5 (Bishop and Anderson Survey). Analysis of Pre-Unit Responses on the Henry Survey The Henry Survey items cover the range of conceptions illustrated in Table 7. I organize the Henry Survey items in Table 8 according to the Conception Categories that they satisfy. Following the Table 8 presentation, I then discuss each survey item by category, and offer analysis of the students entering conceptions based on these categories. Table 8 Biology 11 Students Initial Conceptions based on the Henry Pre-Survey Conception Category Item Number and Statement Percentage of Students Holding: Scientific Alternative Conceptions Conceptions 1. Conceptions about 1. According to the theory of evolution, man evolved from monkeys. 14% 86% what the theory actually says 2. According to the theory of evolution, all organisms are constantly 4% 96% (claims made by evolving. the theory) 3. The theory of biological evolution is used to explain the origin of life. 5% 95% 2. Conceptions about 4. Evolution is a belief held by some scientists but not by all. 19% 81% the nature of science with 5. c) Where would you put the word Evolution on the continuum below 96% 4% respect to (draw a vertical line to represent your choice). evolutionary theory 7. If evolution were true it would be a law not just a theory. 0% 100% 9. The theory of evolution is not testable, because the only way to do that 50% 50% would be to go back into time and actually watch the animals as they change, and there is no way you can do that. 3. Conceptions about 6. The theory of evolution has some holes in it. If organisms were 93% 7% the legitimacy of evolving, you would still be able to see them evolving today, and you evolutionary don't. theory. 61 Table 8 (continued) 4. Conceptions about the relationship between evolution and religion. 8. Evolution is incompatible with religion. 29% 71% 5. Conceptions about the practical applicability of evolutionary theory. 11. Bacteria are evolving resistance to antibiotics faster than we can create new antibiotics to kill them. 12. Evolution theory is used to cure cancer. 100% 47% 0% 53% 6. Conceptions about the nature of science. 13. The word disproof is more valid in science than the word proof. 31% 69% 7. Conceptions about the mechanism of evolutionary 14. The fossil record shows that the ancestors of giraffes did not have long necks. Formulate an explanation for how you think giraffes got their long necks 28% 72% theory (how the theory works -whether Darwinian, Lamarckian, or other). 62 63 Conception Category 1: Conceptions about What the Theory Actually Says (Claims Made By the Theory) Henry Survey items one through three were used to determine students conceptions about what the theory of evolution actually said (the claims made by the theory). Item one dealt with the idea of the distinction between present day monkeys and ancestral primates. A scientific response is that humans and monkeys descended from common ancestors, humans did not evolve from modern day monkeys but rather from ancestral monkey-like primates. Few students held this view at the start of the course. The majority (86%) held that the theory of evolution states that humans evolved from monkeys. They make no distinction between present day monkeys and ancestral primates. One student held that humans did not descend from pre human ancestors. Item two dealt with the idea of whether or not populations are constantly evolving. A scientific response is that population change, as a result of environmental change, can stabilize in a constant (static) environment, and populations need not always evolve. Ninety six percent of the respondents entered the course holding the alternative conception that all organisms are constantly evolving. They did not recognize that sometimes the environment does not change, and therefore without a mechanism for change at work, sometimes the organisms don't change. This may reflect a view that all organisms change all the time. For item three which dealt with the theory of evolution and explanations for the origin of life, the scientific conception is that theories of evolution explain the causes of evolution, how life changes. Theories of origin of life explain how life began. Ninety five percent of surveyed students entered with the alternative conception that 64 evolutionary theory is used to explain the origin of life. Only one student supported the scientific conception that it does not. Conception Category 2: Conceptions about the Nature of Science With Respect To Evolutionary Theory Four items addressed conceptions about the nature of science with respect evolutionary theory. Item four dealt with whether or not evolution was a belief. It addressed the scientific conception that statements of belief that pertain to the scientific process are based on evidence rather than faith. Thus statements of belief acquired while investigating evolution are based on evidence for evolution, rather than faith in evolution. On the pre-test, the majority of students (81%) held alternative views. Forty eight percent equated belief in evolution with an opinion, and reasoned that we all have our own opinions; 33% equated belief in evolution with belief in religion. Some students justified their reasons by saying that some people don't believe in evolution; some believe in God/religion. Item seven was investigating students' conceptions of the role of scientific laws and scientific theories. Laws are not "proven" theories; theories do not become laws once they become "proven". Every respondent held the conception that i f evolution were true it would be referred to as a law. Responses to item four and seven suggest that students may view evolutionary theory in science as underdeveloped, and needing more evidence (research) to become a law (what they appear to regard as the pinnacle of scientific knowledge). Alternatively it may speak to students' interpretation of the terms belief, law and theory. A closer analysis of these students answers indicated that approximately half of the students (58%) indicated that i f evolution were proven it 65 would be escalated to the status of a law (see Figure 10, Appendix C). They see a law as a stronger word for certainty than a theory, and it seems they believe science is based on proof rather than disproof. On item nine, which asks whether evolution is testable, the class was split 50%-50%). Fifty percent of the students held the scientific conception that evolution can be tested. The scientific conception is that testing requires hypothesis formulation and it can be done through experimentation or observation. Testing does not require direct manipulation or perturbation of test subjects. The other half of the class holds the conception that the theory of evolution is not testable because we don't have the ability to observe the postulated changes (and that is what would constitute a test for evolution). Despite their uncertainty about the validity of evolutionary theory, students still regard evolution as part of science (see responses to part c of item 5). Ninety six percent of the respondents held the scientific conception that evolution is science. They appear to think that evolutionary theory is unfinished work, but also think that as time progresses we will be able to fill in any missing data. Students' responses may indicate a view that evolution is a "soft" or imprecise science, which unlike the "hard" sciences, like physics which is based on math, is more plastic (i.e. lacking in precision and accuracy). Conception Category 3: Conceptions about the Legitimacy of Evolutionary Theory Henry Survey item six was used to determine students' conceptions about the legitimacy of evolutionary theory. Item 6 deals with whether evolution provides legitimate explanations. The majority of the students reject the notion that the theory of evolution has some holes in it because organisms cannot be observed to evolve in present 66 day. The scientific conception being examined here is that rates of evolutionary change are observable and calculable in the present day, and hypotheses of common descent can be tested to arrive at conclusions about evolutionary change in the past. We do not have to directly observe a process to explain how that process occurs. Ninety three percent of the respondents held the scientific conception that evolution does not need to be directly observed in order for evolutionary theory to offer legitimate explanations (i.e. have utility as a theory). These responses are in line with responses to part c of item 5 (discussed previously). Conception Category 4: Conceptions about the Relationship between Evolution and Religion Item eight addressed conceptions about the relationship between evolution and religion. This item deals with whether or not students think that evolution is incompatible with religion. The scientific conception as articulated by the National Academy of Sciences (1998 Chapter 5, \ 24) is that "most religions of the world do not have any direct conflict with the idea of evolution". The majority of the students held the conception that evolution is incompatible with religion (71%). This is in line with claims made by the National Academy of Sciences (1998) indicating that many people think that evolution is in conflict with religion, and it is this perceived conflict that results in resistance to the teaching of evolution. 67 Conception Category 5: Conceptions about the Practical Applicability of Evolutionary Theory Conception Category 5 included 2 items dealing with the students' views on the practical applicability of evolutionary theory. Even before instruction all students held the scientific conception that bacteria are evolving resistance to antibiotics. When asked a question that considers the utility of evolutionary theory regarding cancer however, the percentage of students holding the scientific conception was significantly less (47%). On the issue of cancer, the class was almost evenly split with 53% holding the alternative conceptions. Items eleven and twelve both probed for whether students see practical applicability in evolutionary theory. The differences in response may have been due to the fact that students have studied antibiotic resistance prior to taking this unit, but they have not studied the topic of cancer. It may be easier for them to see the link between evolutionary biology and antibiotic resistance based on their prior knowledge; whereas for cancer they could have little prior knowledge, and thus the connection is more difficult to make. Item twelve however is one that may have been interpreted by the students in a way in which I had not intended. My intent was for the item to elicit from students whether or not they thought evolutionary theory had practical applications with respect to the specific case of cancer research. The scientific conception is that evolution has practical application and can be used to inform other areas of science. Evolutionary theory has applications for cancer research just like it has applications for research into antibiotic resistance in bacteria. 68 Looking at the item again, I don't think that it served my intended purpose. Cancer is actually a number of different diseases, and currently there is no generic cure for all cancer. Thus, i f students read the item as saying that evolutionary theory cures cancer, rather than it informs research into curing cancer, they would be correct in stating that evolutionary theory doesn't really cure cancer. Further, i f students interpreted this item in this way, then the cancer item would not be a similar item to the antibiotic resistance item, because it would not be eliciting responses pertaining to the practical applicability of evolutionary theory. I think i f I were to ask this item again, I would need to re-word it in order to more explicitly ask the students i f they think evolutionary theory holds practical applicability in the area of cancer research. Conception Category 6: Conceptions about the Nature of Science The majority of students (69%) held that proof is more valid than disproof and their responses suggest that they think that scientists try to prove their ideas. The scientific conception is that hypotheses are always subject to modification, they can never actually be proven true; however, they can be proven false-that is, they are falsifiable (Mader, 1997). Students seem unaware that hypotheses can only be disproved, and are subject to change as further information comes along. Respondents with alternative conceptions justified their responses by saying it is easier to deny/disprove something than to prove it. It appears that students conceive of proof as the goal of science. They seem to see disproving hypotheses as what we have to settle for until we finally acquire the proof we seek. 69 Conception Category 7: Conceptions about the Mechanism of Evolutionary Theory (How the Theory Works-Whether Darwinian, Lamarckian, or Other) This category dealt with conceptions about the mechanisms of Evolutionary Theory, and was examined with item 14 from the Henry Survey. Item fourteen got students to describe a process of adaptive change, in this case, how giraffes got their long neck. The scientific conception is that adaptive evolution is the result of natural selection acting on heritable variation. Variation in neck lengths exists in the ancestral giraffe population. Environmental factors favored the long neck variation over the short neck variation. The long neck variation enjoyed higher reproductive success, and left more offspring with the trait for long necks in subsequent generations. Twenty eight percent of the respondents held the scientific conception that the giraffe got its long neck through Darwinian processes (selection acting on heritable variation). Seventy two percent of the respondents held the alternative conception that the giraffe evolved its long neck through non-Darwinian methods. Half of the respondents indicated that the giraffe neck length increased through some form of Lamarckian process, via need or stretching, while 22% indicated that the giraffe got it's neck through interbreeding with long-necked organisms (no specification as to type of organism was made). This high student usage of a Lamarckian mechanism as an explanation is in line with previous studies of biology students' views prior to instruction. (Bishop & Anderson, 1990; Brumby, 1984: Demastes, Good, & Peebles, 1995; Demastes, Settlage, and Good, 1995; Jenson & Findley, 1995). 70 Analysis of Pre-Unit Responses on the Bishop and Anderson Survey The Bishop and Anderson items all concern conceptions about the mechanism of evolutionary theory, and thus apply to Category 7: Conceptions about the mechanism of evolutionary theory (how the theory works -whether Darwinian, Lamarckian, or other). To allow for a more in-depth analysis I have separated the items into 4 sub-categories. These are shown in Table 9. In Table 10,1 present the results of my analysis of students' responses to all items on the Bishop and Anderson Survey. Table 9 Conception Category 7) Sub-Categories for Bishop and Anderson Items Conception Sub-Category Dealing Survey Items with Conceptions About: 7a. The mechanism of evolutionary 1 and 2 (Bishop and Anderson Survey), theory (what explanations are used -whether Darwinian, Lamarckian, or other) 7d. The mechanism of evolutionary 3a and 4 (Bishop and Anderson Survey), theory with respect to the role of mutation (the origin of genetic variation). ^ 7c. The mechanism of evolutionary 3b, 3c, and 3d (Bishop and Anderson theory with respect to the role of the Survey), environment (The environment serves to eliminate the unfit). 7d. The usage of the word fitness. 5 (Bishop and Anderson Survey). Table 10 Biology 11 Students Initial Conceptions based on the Bishop and Anderson Survey Conception Sub-Category Dealing with Conceptions About: Item Number and Statement Percentage of Students Holding: Scientific Alternative Conceptions Conceptions 7a. The mechanism of evolutionary theory (what explanations are used -whether Darwinian, Lamarckian, or other) 7b. The mechanism of evolutionary theory with respect to the role of mutation (the origin of genetic variation). 1. Cheetahs (large African cats) are able to run faster than 60 miles per hour 29% when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could only run 20 miles per hour? 2. Cave salamanders are blind (they have eyes which are nonfunctional). 48% How would a biologist explain how blind cave salamanders evolved from sighted ancestors? 3a. Ducks are aquatic birds. The them fast swimmers. Biologists birds which did not have webbec ir feet are webbed and this trait makes explain that ducks evolved from land feet. The trait of webbed feet in ducks: Appeared in ancestral ducks because they lived in water and needed webbed feet to swim. 12345 Appeared in ducks because of a chance mutation. 4. A number of mosquito populations are today resistant to DDT, even though those species were not resistant to DDT when it was first introduced. Biologists would explain that DDT resistance evolved in mosquitos because: (choose the best answer) a. Individual mosquitos built up an immunity to DDT after being exposed to it. b. Mosquitos needed to be resistant to DDT in order to survive. c. A few mosquitos were probably resistant to DDT before it was ever used. d. Mosquitos learned to adapt to their environment. e. Other; please explain 71% 52% 0% 100% 12% 88% 71 Table 10 (continued) Conception Sub-Category Dealing with Conceptions About: Item Number and Statement Percentage of Students Holding: 3b. Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists explain that ducks evolved from land birds which did not have webbed feet. While ducks were evolving webbed feet: With each generation, most ducks had about the same amount of webbing on their feet as their parents. 12345 With each generation most ducks had a tiny bit more webbing on their feet than their parents. Scientific Conceptions Alternative Conceptions 7c. The mechanism of evolutionary theory with respect to the role of the environment 3c. Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists explain that ducks evolved from land birds which did not have webbed feet. If a population of ducks were forced to live in an environment where water for swimming was not available: Many ducks would die because their feet were poorly adapted to this environment. 12345 The ducks would gradually develop nonwebbed feet. 3d. Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists explain that ducks evolved from land birds which did not have webbed feet. The population of ducks evolved webbed feet because: The more successful ducks adapted to their aquatic environment. 12345 The less successful ducks died without offspring. 32% 68% 46% 54% 43% 57% 72 Table 10 (continued) Conception Sub-Category Dealing with Conceptions About: Item Number and Statement Percentage of Students Holding: Scientific Alternative 7d. The usage of the 5. Biologists often use the term "fitness" when speaking of evolution. 25% 75% word fitness. Below are descriptions of four male lions. According to your understanding of evolution, which lion would biologists consider the "fittest"? Name George Ben Spot Sandy Size 10 8 9 feet/162 lbs 9feet/160 lbs feet/1751b feet/160 s lbs Number of 19 25 20 20 cubs fathered Age of 13 years 16 years 12 years 9 years death Number of 15 14 14 19 cubs surviving to adulthood Comments George is Ben has When the area that Sandy was very the Spot lived in was killed by an large, greatest destroyed by fire, infection very number Spot was able to resulting from a healthy. of move his pride to cut on his foot. The females a new area & strongest in his change his feeding lion. harem. habits. The "fittest" lion is: a. George b. Ben c. Spot d. Sandy 73 74 Conception Category 7a: Conceptions about the Mechanism of Evolutionary Theory (How the Theory Works-Whether Darwinian, Lamarckian, or Other) Items in this category on the Bishop and Anderson Survey dealt with the views on the mechanisms of evolution. The majority of the students held the alternative conception that adaptive evolution proceeds through some sort of Lamarckian mechanism. The scientific conception for item one on adaptive evolution in cheetah speed is that adaptive evolution in cheetah speed is Darwinian (natural selection acting on heritable variation). The scientific conception for item 2 on the evolution of blind cave salamanders is that loss of sight in cave salamanders is Darwinian (absence of natural selection acting = accumulated mutations). The results from the item on the evolution of cheetah speed (Bishop and Anderson Survey item one) were similar to the results from the responses to the item on the Henry Survey dealing with the evolution of neck length in giraffes. Over half of the respondents (59%) held that cheetah speed increased through some form of Lamarckian evolution (Figure 22, Appendix C). The salamander item required students to reason out what happens to a trait in the absence of environmental pressures (i.e. factor in spontaneous mutation). Forty eight percent of the respondents held a scientific conception by proposing a genetic based mechanism for loss of sight. Some of these students offered a Darwinian explanation that mutations accumulating in the eyes no longer effected survival (14%). Others (33%) used a Mendelian explanation that genes affect traits, and that blindness was caused by a mutated gene which subsequently spread in the population (discrepancies due to rounding). Fifty two percent of the respondents held the alternative conception that cave 75 salamanders lost their sight through a non Darwinian mechanism. To explain their alternative conception, some students (24%) presented the Lamarckian mechanism that lack of use made the organ less able to do its job, and this less able trait was passed on to offspring. Others (24%) held that the salamanders went blind through non-use of their eyes and thus developed other senses to compensate (another Lamarckian explanation). One student offered a catastrophe as a mechanism by explaining that blindness was due to a mass epidemic that affected the salamander population (Figure 24, Appendix C). Conception Category 7b: Conceptions about the Mechanism of Evolutionary Theory With Respect To the Role of Mutation (The Origin of Genetic Variation) Students in this study did not appear to understand the role of mutations in originating genetic variation. For the items dealing with ducks' webbed feet and mosquito populations on the Bishop and Anderson Survey, the majority of student's proposed Lamarckian mechanisms to account for the origin of new traits. For item 3a dealing with ducks webbed feet, the scientific conception is that webbed feet appeared in ducks because of a chance mutation. For item 4 dealing with mosquitos developing resistance to pesticide, the scientific conception is that a few mosquitos were probably resistant to DDT before it was ever used. Every student surveyed offered the alternative conception that webbed feet appeared because ducks needed webbed feet to swim. Many of the responses however suggested a combination of need plus mutation. For example, some students said need is the driving force (29%), while others (36%) said that need is the driving force but mutation plays a role as well. Another subset of students (29%) felt that it is the combination of both that produces novel traits, and a smaller subset (7%) 76 said that although mutation is the driving force, need still plays a role (Figure 26, Appendix C). For the mosquito item, most of the respondents (88%) held an alternative conception that the novel trait appeared by some mechanism other than spontaneous mutation. Only twelve percent held the scientific conception that mutation was already in the population before DDT exposure. Nearly half of the students (46%), suggested that the mosquitos built up immunity to DDT after being exposed (Figure 34, Appendix C). Student responses to both these items suggest they adopted a teleological view of evolution whereby traits appear in order to serve a purpose (rather than appear spontaneously). Conception Category 7c: Conceptions about the Mechanism of Evolutionary Theory With Respect To the Role of the Environment (The Environment Serves to Eliminate the Unfit) This category dealt with three items that examined student's understandings of the role of the environment in evolutionary change. For item 3b, roughly about one third of the students held the scientific conception that with each generation most ducks had about the same amount of webbing on their feet as their parents. The scientific explanation is that after selection has acted, offspring, relative to their parents, will possess on average the same degree of a trait, however, relative to the whole parent generation; offspring will possess slightly more of that trait. In the duck example, it is the frequency of individuals possessing the increased webbing (quantity) that increases in 77 the next generation, the amount of webbing (quality) does not increase in each individual in the next generation. Sixty eight percent of the respondents offered some form of alternative explanation related to the idea that with each generation most ducks had a tiny bit more webbing on their feet than their parents. The majority of students (50%) proposed explanations that were a combination of the alternative views and the scientific views (Figure 28, Appendix C). They explained that most ducks possess more webbing than their parents, but there were also a high number of ducks that possessed the same amount of webbing. These students appeared to think that adaptive evolution occurs because the trait gradually changes in a directional manner, with each individual having slightly more of the successful trait than their parents. They didn't appear to recognize that the offspring generation possesses on average, the same degree of variability in a trait as their parents, and that parents who possess successful traits contribute more offspring to the next generation than parents who possess unsuccessful traits. They also seemed unaware that it is not the quality of a trait that increases in a population; it is the quantity of individuals possessing the trait that increases. For the item that examined how environmental changes affect ducks, forty six percent held the scientific conception that if the environment changed many ducks would die. A slight majority (54%) of the respondents, held the alternative conception that the ducks would gradually develop webbed feet. Many of the respondents (32%) offered a combination of the alternative and scientific explanations (Figure 30, Appendix C). They proposed that environmental pressure would have a greater effect at causing a population to evolve rather than causing individuals to die. They appear to think that organisms well 78 adapted to a particular niche would evolve new traits rather than die out when that niche was eliminated. For the item comparing ducks to land birds, 43% of the students held the scientific conception that the less successful ducks died without leaving offspring. They see the environment as eliminating the unfit. The remainder of the students (57%) held the alternative conception that the more successful ducks would adapt. These students appeared to conceive of the role of the environment as promoting the fit as opposed to eliminating the unfit. Conception Category 7d: Conceptions about the Usage of the Word Fitness One quarter of the students offered the scientific explanation that fitness means having the most offspring reach reproductive maturity. Seventy five percent held alternative conceptions. Many of the respondents (46%) held that the fittest individual was "Spot" because he was able to relocate his pride after a fire. According to Bishop and Anderson (1986), students who see the evolutionary process as a process of individuals changing in response to a stimulus, will select Spot. These students appear to view fitness as the ability to adapt to ones environment during ones lifetime. Summary of Biology 11 Students Initial Conceptions (Based On Analysis of the Bishop and Anderson Survey) Before the evolution unit was taught, the majority of students in my study held non scientific responses to all 8 of the items on the Bishop and Anderson Survey (see Table 10). Their responses suggest that student thinking about adaptive evolution is very 79 teleological. My students see traits appearing because the traits are needed; they see traits (and the organisms possessing these traits) as changing because the change serves a purpose. Their explanations of purpose and need match the early explanations of Lamarck who built his theory of use and disuse, and inheritance of acquired characteristics using these arguments. Also, my students see the role of the environment as additive or helpful (selecting for favorable traits) rather than eliminative (selecting against unfavorable traits). This teleological thinking matches the way humans engage in selective breeding. We select with a purpose, the organisms that we want to breed, and breed for a trait we favor. Chapter Summary The findings for the Henry Survey and the Bishop and Anderson Survey support previous research conducted on students' conceptions of evolution. These British Columbia students entered my Biology 11 course with a variety of conceptions about the world around them. If these conceptions are not addressed, they may leave my course with their initial conceptions intact. The next chapter examines the impact of the conceptual change approach I adopted for the teaching of the Evolutionary Biology unit. I consider whether students' conceptions of evolution change after they experience a unit on evolution, and discuss i f this teaching unit was able to support the students' development of scientific conceptions. CHAPTER SIX RESEARCH QUESTION TWO: ANALYSIS OF A CONCEPTUAL CHANGE APPROACH TO TEACHING EVOLUTION This chapter addresses the second research question: Can teaching an evolutionary biology unit, based on conceptual change instructional approaches, help students negotiate conceptual change and acquire scientific conceptions? Similar to my treatment of the first research question, I summarize my research pertaining to this question, and offer an analysis of the results. My findings are based on an analysis of responses to the Henry and the Bishop and Anderson Surveys, which were administered after I taught a unit on Evolution. In my discussion I look in detail at the responses, and consider students' scientific and alternative conceptions. I close this chapter with a look at alternative conceptions that arise following my instruction. These conceptions were not in evidence in the pre-unit responses, and are thus referred to as New Alternative Conceptions. The complete set of data showing the survey items and responses are included in Appendix C. As discussed in Chapter 3, to evaluate the success of my conceptual change approach to teaching about evolution, I looked at 2 criteria. 1) the number of students that use scientific conceptions in their explanations post the teaching of the evolution unit, and 2) whether the degree of change of students use of scientific conceptions in their survey responses appears large or small (in relative terms). Using the criteria as a guide, I developed the table of Scientific Conception Use levels (refer to Table 11). The table is designed to organize the scientific conception usage into different categories from high 81 (>50% usage) to low (or a decrease) based on student use of the scientific conceptions in their responses to survey items post unit. Items designated as Use Level 1 represent survey items which I categorized as showing a high scientific conception usage post-unit. For these items the usage of the scientific conception increased, and the scientific conception was used by the majority of the students (scientific conception used by >50%). Items designated as Use Level 2 represented a moderate use of scientific conception, where the scientific conception increased and was used by <50% of the students. Items designated Use Level 3 represented a minimal scientific conception usage, where the usage of the scientific conception showed only a very slight increase (<10%), and the conception was used by <50% of the students (note 10% represents 2-3 students). Items designated Use Level 4 represented a decrease in scientific conception usage. My analysis of the success of the unit will come from analyzing the student responses to items as organized into these Scientific Conception Use Levels. 82 Table 11 Use Levels Scientific Conception Use Levels Survey Items 1. Level 1: High scientific conception usage. The usage of the scientific conception increased; and the scientific conception was used by the majority of the students (>50%). 1,8, 9, 12, 14 (Henry Survey). 1, 2, 3d (Bishop and Anderson Survey). 2. Level 2: Moderate scientific conception usage. The usage of the scientific conception increased, and the scientific conception was used by <50% of the students. 2, 3, 4, 7 (Henry Survey). 3a, 4, (Bishop and Anderson Survey). 3. Level 3: Minimal scientific conception usage. The usage of the scientific conception increased minimally (<10%), and the scientific conception was used by <50% of the students. 3b, 3c, 5 (Bishop and Anderson Survey). 4. Level 4: Decrease in scientific conception usage. 13 (Henry Survey). In the next section of this chapter I discuss the students' responses as organized by these Use Levels. Starting with Use Level 1 and proceeding to Use Level 4,1 try to identify patterns in, and offer explanations for, the increases or decreases in student usage of scientific conceptions based on this organization of Use Levels. I will offer reasons for whether or not the course appeared successful in getting the majority of students to use the scientific conception. I will also discuss why some conceptions seemed more difficult to change than others (based on the change in % usage), and whether or not the course was successful in facilitating conceptual changes. 83 Discussion of Scientific Conception Use Levels 1 Through 4 Scientific Conception Use Level 1 -High Scientific Conception Usage For a number of items, scientific conception use was high with more than half the students using scientific explanation in their post unit explanations. These items were assigned to Scientific Conception Use Level 1. A summary of frequency of student responses to these items is shown in Table 12. What this table also shows is the percentage of responses (pre and post) where students were using scientific explanations, and the difference between pre and post unit usage. Responses to items 1 and 14 on the Henry Survey showed the highest post-unit usage of the scientific conception, as well as the highest pre-post percent changes; suggesting that conceptual change was easily facilitated. In their responses to item 1, students were able to distinguish between modern day monkey and ancestral primates, and present the concept of descent from a common ancestor as an explanation for the similarities observed between man and monkey. For item 14, students' responses indicate a shift from Lamarckian explanations to Darwinian conceptions. Typical student responses indicated that selection works on variation in a population, for example one student wrote: "Giraffes had lengths of varying necks. The ones with longer necks were better equipped for survival so they had more offspring, some with longer necks, than the other which were gradually dying off. Eventually all of the giraffes had long necks because other wouldn't survive." Further, the pre-unit idea that giraffes mated/interbred with a long necked organism did not appear in any post-unit responses. Item 12 on the Henry Survey that dealt with the relationship between evolution and cancer had majority usage in scientific conception, yet elicited the smallest increase 84 for this Use Level (18%). The limited increase may be due to the fact that in the Evolution unit, we did not focus directly on cancer. Alternatively as proposed in chapter 5, the students' responses may simply represent their confusion in interpreting the meaning of the item (I offer comments about item re-design in the conclusion chapter of this report). Items 8 and 9 on the Henry Survey showed increases in use of scientific conceptions of 34% and 29% respectively; suggesting that conceptual change was moderately easy to facilitate. Students appear to have shifted from the view that concepts of evolution are in conflict with religion. In their post unit responses there was an increase in students suggesting options for testing evolution. For example the post-unit survey showed an increase in the number of students proposing that evolution can be tested by reconstructing past changes through fossils, as well as an increase in the number of students suggesting that evolution can be tested by studying microevolution. The students references to microevolution appeared to be related the Hardy Weinberg material taught in class. One student wrote "It is because you can test allele frequencies of generations". Another offered "Using the Hardy-Weinberg Law we can use mathematics to test whether or not evolution has occurred in a population." Analysis of Bishop and Anderson Survey items 1, 2, and 3d also showed the majority of the students using scientific conceptions, in their answers. On item 1, the majority of students offered a Darwinian explanation to account for cheetah speed; use of this conception increased by 42% Pre-unit responses posing the alternative conceptions that adaptive evolution is due to mating/interbreeding with fast organisms and that Biologists are operating on 85 assumption (rather than evidence) did not appear in the post-unit survey responses. One alternative conception persisted. It was the idea that cheetah speed evolved because the cheetahs decided to, or tried to, get faster. This explanation however dropped in usage. For items 2 on the Bishop and Anderson Survey there was an overall increase in scientific conception usage of 12%. Despite this increase, use of a Mendelian genetics explanation decreased by 6% and use of a Lamarckian explanation of evolution increased by 16%> (See Figure 24 in Appendix C). However, the Lamarckian view that included an explanation about salamanders developing senses to compensate for blindness did not appear in the post-unit responses, and no student suggested a mass epidemic caused blindness. The 12%o increase in use of the scientific conception for item 2, suggests that students have difficulty figuring out what happens to a trait in the absence of environmental pressures. That is, they have difficulty factoring in the effect of spontaneous mutation. Students return to their entering and familiar conceptions to explain a novel situation. Item 3d showed a 21% increase in the number of students using the scientific conception. This suggests the conceptual change was moderately easy to facilitate. Students appeared to have embraced the scientific conception that the less successful ducks die without leaving offspring in the face of a drastic environmental change, over the alternative conception that the more successful ducks adapted to a drastic environmental change. Students appeared to grasp the concept that survival of the fittest implies elimination of the unfit, and that after selection has occurred, the individuals who remain are referred to as the fittest. The concept is often difficult for students to grasp in that it is counter-intuitive. For example, when humans selectively breed domestic animals or plants, we select for favorable traits. When the environment selects, it selects against unfavorable traits. In my teaching I did not directly address the concept of artificial selection vs. natural selection or the subtle difference between the two. However, students were able to use the scientific conception to negotiate this item post-unit. 87 Table 12 Scientific Conception Use Level 1 -High scientific conception usage. Survey Items % Scientific Conception % Change in Use Pre Post %(+)or(-) Unit Unit Henry Survey 1. According to the theory of evolution, man evolved from monkeys. 14% 93% +79% 8. Evolution is incompatible with religion. 29% 63% +34% 9. The theory of evolution is not testable, because the 50% 79% +29% only way to do that would be to go back into time and actually watch the animals as they change, and there is no way you can do that. 12. Evolution theory is used to cure cancer. 47% 65% +18% 14. The fossil record shows that the ancestors of 28% 91% +63% giraffes did not have long necks. Formulate an explanation for how you think giraffes got their long necks. Bishop and Anderson Survey Cheetahs (large African cats) are able to run faster than 60 miles per hour when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could only run 20 miles per hour? 29% 71% +42% 2. Cave salamanders are blind (they have eyes which are nonfunctional). How would a biologist explain how blind cave salamanders evolved from sighted ancestors? 48% 60% +12% 3d. Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists explain that ducks evolved from land birds which did not have webbed feet. The population of ducks evolved webbed feet because: 43% 64% +21% The more successful ducks adapted to their aquatic environment. 12345 The less successful ducks died without offspring. 88 Scientific Conception Use Level 2 -Moderate Scientific Conception Usage Table 13 provides a summary of items on both Survey instruments that elicited moderate scientific conception use. Students' responses for item 2 on the Henry Survey suggested an increased awareness of scientific mechanisms that can provide evolutionary change. New scientific conceptions that appeared in students' responses on the post-unit survey included reference to change caused by environmental pressure, by violation of the Hardy Weinberg principle, and by organisms adapting. The commonly stated alternative conception, that organisms are constantly evolving to keep up with a continually evolving environment, decreased in usage. For item 3 on the Henry Survey, the increase in usage of the scientific conception is possibly due to more students defining evolution as change over time. Thus at the end of the unit students could distinguish between theories that explain how organisms change, and theories that explain how life first started. Responses to item 4 on the Henry Survey indicate that students shifted from explanations of evolution as a metaphysical belief to evolution being an evidence based belief. The greatest shift was away from students thinking evolutionary theory was an opinion. The increase in scientific conception use for item 7 on the Henry Survey reflects several conceptual shifts. First, students appear to be able to differentiate between a law and a theory and explain that they are two different things. Second, use of the popular alternative conception that i f evolution were true it would be a law by now, decreased. Third, students abandoned some of their entering alternative conceptions. For example 89 the idea that evolution is yet to be proven, the idea that evolution should be a law, and the idea that evolution did not really occur, have all dropped to 0% usage on the post-unit survey. Three of the increases in scientific conception usage represented students gaining the ability to differentiate between two previously undifferentiated concepts; origin versus evolution of life (item 3); evolution as a metaphysical belief versus evolution as an evidence based belief (item 4); and theory versus law (item 7). Once students were made aware that differences exist, they were able to draw upon their understanding of those differences when considering questions about evolution. Responses to item 3 on the Henry Survey indicated that many students still view the theory of evolution as an explanation for the origin of life. This suggests pre-unit alternative conceptions on this idea are very persistent. For item 3 a on the Bishop and Anderson Survey, which dealt with the appearance of a novel trait, the majority of the class retained aspects of Lamarckian explanations. While purely Lamarckian explanations decreased, such as ducks needing to change, than trying to satisfy this need, the majority of the students stated that novel traits appear due to a combination of both need and mutation. For item 4 on the Bishop and Anderson Survey, which again dealt with the appearance of a new trait in the population, the increase in the use of the scientific explanation paralleled a decrease in use of most of the alternative conceptions. There was a decrease in use of the explanations that mosquitos became immune to DDT after exposure, that organisms change because they need to change, and that mosquitos learned to adapt to environment decreased. Even following a unit of instruction, most students still reasoned that it is after DDT exposure that mosquitos build up immunity to the DDT. Items 3a and 4 dealt with conceptions about the mechanism of evolutionary theory with respect to the role of mutation, and the origin of genetic variation; and both items examined students' teleological thinking. The items compared the Lamarckian view that traits appear in order to serve a purpose, with the modern evolutionary view that traits appear as a result of mutation. Few students were able to use the scientific conception, that mutations are the source of genetic variation (novelty), in their answers. Many still supported the alternative conception that traits appear to fulfill some purpose for the organism; they claimed in item 3a that purpose is to satisfy the ducks' need to swim, in item 4 that purpose is to make mosquitos resistant to DDT. When faced with questions like these, rather than reason through a difficult scientific conception to arrive at an answer, it appears that students adopted their prior alternative conceptions in their explanations. The degree of novelty of an example appears to be influential in determining whether students choose to use a scientific conception, or stay with their alternative conception. The responses of my students suggest that more time may need to be spent on the concept of origin of variation. Alternatively more practice with novel questions might help students make the cognitive leaps. Table 13 Scientific Conception Use Level 2 -Moderate scientific conception usage. Survey Items % Scientific Conception usage % Change in Use Pre Post %(+)or Unit Unit (-) Henry Survey 2. According to the theory of evolution, all organisms are constantly evolving. 4% 42% +38% 3. The theory of biological evolution is used to explain the origin of life. 5% 38% +33% 4. Evolution is a belief held by some scientists but not by all. 19% 44% +25% 7. If evolution were true it would be a law not just a theory. 0% 46% +46% Bishop and Anderson Survey 3a. Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. 0% 21% +21% Biologists explain that ducks evolved from land birds which did not have webbed feet. The trait of webbed feet in ducks: Appeared in ancestral ducks because they lived in water and needed webbed feet to swim. 12345 Appeared in ducks because of a chance mutation. 4. A number of mosquito populations are today resistant to DDT, even though those species were not resistant to DDT when it was first introduced. Biologists would explain that DDT resistance evolved in mosquitos because: (choose the best answer) a. Individual mosquitos built up an immunity to DDT after being exposed to it. b. Mosquitos needed to be resistant to DDT in order to survive. c. A few mosquitos were probably resistant to DDT before it was ever used. d. Mosquitos learned to adapt to their environment. e. Other; please explain 12% 32% +20% 91 92 Scientific Conception Use Level 3 -Minimal Scientific Conception Usage. Table 14 summarizes item responses that I categorizes as minimal use of scientific explanations. The responses were associated with the Bishop and Anderson Survey items 3b, 3c, and 5. The less than 10% increase in the usage of the scientific conception indicated that these alternative conceptions were persistent and difficult to change. In the discussion that follows I consider some of explanations for this low increase in usage of scientific conceptions after instruction was implemented. Responses to item 3b, suggest that students think that gradual increase in a trait is a result of the quality of the trait increasing, rather than the quantity of individuals possessing the trait increasing. Responses to item 3 c also showed a minimal increase in student usage of scientific conception after the unit. This suggests that students think that organisms well adapted to a particular niche would evolve new traits rather than die out when that niche was eliminated. For item 5, although scientific conception use showed little change after the unit, the students in this category did shift from one alternative conception to another. That is, students shifted from the pre-unit idea that the fittest is the strongest, to the conception that fitness indicates that an organism can adapt to changes within its lifetime. The low increase in usage of the scientific conception on this item may be attributed to the fact that students were not directly taught the definition of fitness. The concept of fitness was mentioned in our unit of instruction, but it was never explicitly defined as the ability to bring offspring to reproductive maturity. Upon reflection, I see this as an oversight in the design of my unit. Fitness should have been explicitly defined for the students. It is 93 apparent that students currently leave my course with their alternative conceptions of fitness intact. Some results on these items may be attributed to the wording of the items which deal with quite complex concepts. Item 3b dealt with the concept of the nature of inheritance, and the intricacies of how adaptations progress in a selecting environment. Organisms are born similar to their parents. The trend towards more webbing is only apparent because after nature selects against the non-webbed toed trait, individuals with slight or moderate webbing survive. Item 3c presents another difficult concept in that students must realize that the population is small, before they can understand that a drastic environmental change will result in death of the individuals rather than adaptation of the population. Table 14 Scientific Conception Use Level 3 -Minimal scientific conception usage. Survey Items % Scientific % Change Conception in Use usage Pre Post % (+) or Unit Unit (-) Bishop and Anderson Survey 3b. Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists explain that ducks evolved from land birds which did not have webbed feet. While ducks were evolving webbed feet: 32% 37% +5% With each generation, most ducks had about the same amount of webbing on their feet as their parents. 12345 With each generation most ducks had a tiny bit more webbing on their feet than their parents. 3c. Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists explain that ducks evolved from land birds which did not have webbed feet. If a population of ducks were forced to live in an environment where water for swimming was not available: 46% 50% +4% Many ducks would die because their feet were poorly adapted to this environment. 12345 The ducks would gradually develop nonwebbed feet. 94 Table 14 (continued) 5. Biologists often use the term "fitness" when speaking of evolution. Below are descriptions of four 25% 29% +4% male lions. According to your understanding of evolution, which lion would biologists consider the "fittest"? Name George Ben Spot Sandy Size 10 feet/1751bs 8 feet/160 lbs 9 feet/162 lbs 9feet/160 lbs Number of cubs 19 25 20 20 fathered Age of death 13 years 16 years 12 years 9 years Number of cubs 15 14 14 19 surviving to adulthood Comments George is very Ben has the When the area Sandy was killed by an large, very greatest number that Spot lived infection resulting from a healthy. The of females in in was cut on his foot. strongest lion. his harem. destroyed by fire, Spot was able to move his pride to a new area & change his feeding habits. The "fittest" lion is: a. George b. Ben c. Spot d. Sandy 95 96 Scientific Conception Use Level 4 -Decrease in Scientific Conception Usage The item assigned to Use Level 4 was one that elicited a decrease in scientific explanations (see Table 15), the usage of scientific conceptions decreased by 7%. Thus alternative conceptions increased following instruction in this unit. Students completed the course holding the conception that scientists look for proof, but since proof is such a difficult thing to attain, scientists settle for disproving themselves or other scientists. As far as difficulty goes, this conception classifies as a very difficult change to make. The minimal usage of the scientific conception by my students may be due, in part, to poor wording of the item on my part. I hoped to distinguish between the concept of proving hypotheses, and disproving hypotheses, but students were unable to articulate the difference. This item may benefit from a re-wording to more explicitly ask students to define the role of proof and disproof in hypothesis testing. Item 13 probed students' conceptions about the nature of science in regard to hypothesis testing and falsifiability. Although in my unit I dealt with the nature of science in the context of evolutionary theory and considered hypothesis testing and falsifiability of evolutionary theory, I was not explicit with linking falsifiability with evolutionary theory. Nature of science concepts were taught at the beginning of the year in a unit on the scientific method, and I expected that students would build on their prior knowledge about the nature of science in this evolution unit. That did not happen. Students did not link ideas about falsifiability and the nature of science with falsifiability in evolutionary theory. This result supports other research indicating that alternative conceptions concerning the nature of science are strong, and deeply held. Even in a course designed 97 to address alternative conceptions, these conceptions remain intact in students. Indeed nature of science conceptions have been identified as one of the hurdles affecting scientific literacy in general, and in understanding of evolutionary theory in particular (The National Academy of Sciences, 1998). My study finding suggests that a conceptual change unit explicitly dealing with nature of science conceptions may be necessary if we wish to help students increase their usage of scientific conceptions in this area. Table 15 Scientific Conception Use Level 4 -Decrease in of scientific conception usage. Survey Items % Scientific % Change Conception in Use usage Pre Post %(+) or(-) Unit Unit Henry Survey 13. The word disproof is more valid in science than 31% 24% -7% the word proof. Overall my findings suggest that the Evolution Unit I designed was moderately successful, in affecting conceptual change for the majority of concepts measured by the Henry Survey. The findings also suggest that this unit was moderately successful, in promoting conceptual change for the majority of concepts measured by the Bishop and Anderson Survey. 98 New Alternative Conceptions Alternative conceptions do not necessarily get extinguished during a conceptual change process. Often times they get incorporated into the learners new scientific conceptions. This incorporation of old with new may result in the learner using a more scientific explanation, but it may also result in the learner just presenting a jumble of scientific and alternative conceptions in their explanations (Wandersee, Mintzes, Novak, 1994). Most studies show that the best that usually can be achieved is some sort of hybrid conceptual change where elements of the entering conception merge with the elements of the scientific conception (Duit & Treagust, 1998). In this study following the teaching of my Evolution Unit, I identified a number of New Alternative Conceptions (NAC's) that were not evident on the pre-unit survey data set. New alternative conceptions were evident in students' responses to items 2, 6, 7, 8, and 14 on the post-unit Henry Survey, and in items 1 and 2 of the Bishop and Anderson Survey. In what follows I discuss each of the N A C ' s that arose from my analysis of these items. Three new alternative conceptions N A C ' s were evident in student responses to this item 2 on the Henry Survey (see Table 16). In N A C 1, the student reasons that all organisms are not constantly evolving (scientific conception), because organisms have "finished evolving" (alternative conception). In the N A C 2, the students' present teleological arguments reasoning that some organisms don't need to change. This conception represents a mix of a teleological explanation that evolution is goal directed and the scientific conception that not all organisms change all the time. The students offering alternative viewpoint N A C 3 use the Hardy Weinberg principle to put forth an 99 explanation that all organisms are constantly evolving. In our unit we studied population equilibrium, and students learned that populations rarely stay in equilibrium. The factors that violate Hardy Weinberg equilibrium are continuously in play, and if they cause change in allele frequency, they cause evolution. Incorporating this knowledge, this student used the scientific conception of violating Hardy Weinberg to accept the alternative conception that populations are constantly evolving (when in fact it is Hardy Weinberg theorem that explains why populations remain stable). Item 6 on the Henry Survey was concerned with observing large long term evolutionary change. This item elicited the alternative conception that evolution only occurs when there is a new organism. This new alternative conception N A C 4 appears to be one student's novel interpretation of speciation. We studied allotropic speciation (geographic isolation followed by reproductive isolation) and compared gradual change vs. punctuated equilibrium. We discussed how the fossil record shows sudden (geologically speaking) species changes as opposed to one species gradually turning into another, validating the punctuated equilibrium model. This student may have equated speciation with evolution, and may reason that evolution (as speciation) only occurs when there is a new organism. Item 7 on the Henry Survey compared the terms law and theory as they apply to evolution, and elicited N A C 5 that a theory is better than a law. In our course I tried to distinguish between the concepts of law and theory, both in science contexts and everyday. The goal was to show that these terms refer to distinct concepts in science, with separate meanings. One student's response suggests she sees that the different definitions exist (scientific conception), but regards law and theory on a continuum 100 (alternative conception), with a scientific theory being a stronger word for certainty than a law. Item 8 of the Henry Survey investigated whether students perceive evolutionary theory as being in conflict with religion. One student responded that evolution is not incompatible with religion because evolution explains how organisms change, and religion explains how life originated. This N A C 6 may be an outgrowth of a class discussion of evolution and the origin of life. We considered the view that evolutionary theory does not explain how life originated; it explains how life changed from one form to another. Change in allele frequencies presupposes alleles in the first place. This student appears to hold the conception that evolution is not in conflict with religion. She also agrees with the conception that evolution does not explain the origin of life, and with the concept that religion proposes explanations for the origin of life. The implication though, is that there are no explanations for the origin of life other than religious ones. Item 14 on the Henry Survey explores students' conceptions of mechanisms for adaptive change over geological time. Students explain that giraffes needed long necks; the ones who got these long necks satisfied this need and passed this on to their offspring. The students' N A C 7 appears to be a mixture of Darwinian mechanisms and teleology (survival plus need). It does not include the Lamarckian conception of use and disuse, and inheritance of acquired characteristics. It does however, appear to be based on the idea that the need for food is a factor in the evolution of the trait, and that the giraffes evolved their traits to satisfy this need. Here a teleological view point (alternative 101 conception) is included with the scientific conception (natural selection) as a hybrid explanation. Item 1 on the Bishop and Anderson Survey explores students' conceptions of mechanisms for adaptive change over geological time. This N A C 8 is similar to the students' conceptions regarding the giraffe neck length from the Henry Survey. Here again this N A C combines the Darwinian idea of survival with a teleological view of need. It includes the idea that the need for speed is a factor in the evolution of the trait, and that the cheetahs evolved their traits to satisfy this need. Item 2 on the Bishop and Anderson elicited explanations for how vestigial structures might arise. Students presented N A C 9 that vestigial structures arise through Lamarckian disuse. New Alternative Conception 9 may have arisen through our discussion of vestigial structures in class. Students learned that a vestigial structure is a structure which is greatly reduced in form and or function. I presented vestigial structures as evidence of common descent, but did not elaborate on the genetics of how vestigial structures arise. That is, students were not told that they arise through mutations accumulating in a structure that no longer has a selective advantage (or has a reduced selective advantage). Without knowledge of this mechanism, students appear to have taken a Lamarckian explanation and presented it as the mechanism for vestigial structures; that is, vestigial structures arise through disuse. One student put it this way "There were cave salamanders with vision and cave salamanders with no vision. And through Lamarck's theory of use & disuse, the salamanders eventually stop using them." Students argued that the vestigial structures, which are evidence for common descent 102 (scientific conception); arise through disuse, and inheritance of acquired characteristics (alternative conception). Table 16 New Alternative Conceptions Survey Item New Alternative Conceptions Revealed (NAC) Henry Survey 2. According to the theory of evolution, all organisms are constantly evolving. N A C 1 -Organisms are no longer evolving, so not all organisms change. N A C 2 -Some organisms don't need to change, so not all organisms change. N A C 3 - A l l organisms change due to the factors that violate Hardy Weinberg. 6. The theory of evolution has some holes in it. If organisms were evolving, you would still be able to see them evolving today, and you don't. N A C 4 -Evolution only occurs when there is a new organism. 7. If evolution were true it would be a law not just a theory. N A C 5 -A theory is better than a law. 8. Evolution is incompatible with religion. N A C 6 -Evolution and religion are not incompatible because religion talks about origin of life, and evolution doesn't. 14. The fossil record shows that the ancestors of giraffes did not have long necks. Formulate an explanation for how you think giraffes got their long necks. N A C 7 - A mixture of Darwinian mechanisms and teleology (survival plus need). Giraffes needed to reach food, the ones that did enjoyed higher reproductive success, and they passed their genes on to the next generation. Bishop and Anderson Survey 1. Cheetahs (large African cats) are able to run faster than 60 miles per hour when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could only run 20 miles per hour? N A C 8 - A mixture of Darwinian mechanisms and teleology (survival plus need). Cheetahs needed to get faster, the ones that did enjoyed higher reproductive success, and passed their genes on to the next generation. 2. Cave salamanders are blind (they have eyes which are nonfunctional). How would a biologist explain how blind cave salamanders evolved from sighted ancestors? N A C 9 -Vestigial structures arise through the Lamarckian mechanism of use and disuse. 103 Implications of New Alternative Conceptions. An interesting set of N A C s were the teleology/Darwin hybrids. Analysis of the responses for item 14 from the Henry Survey, and 1 from the Bishop and Anderson Survey, indicated students incorporated teleology into their Darwinian explanations. Item 2 from the Bishop and Anderson Survey shows students again using a teleology/Darwin explanation. It seems the idea of organisms needing to change is a compelling one. Students see organisms as changing for a purpose, and Darwinian selection is the way they fulfill that purpose. I am not sure i f this inclusion of need is teleological thinking or just teleological writing however. We speak in teleological terms all the time as a way of expressing our ideas. For example when I say that sodium chloride (NaCl) forms because chlorine "needs" one more electron to "satisfy" it's octet, and sodium "needs" to get rid of one to "satisfy" it's octet, and when brought into the correct environment, that is exactly what they do; I don't mean it in a teleological way. I don't mean that chlorine or sodium are acting purposefully by undergoing chemical reactions. I'm just describing, in a convenient and plainly spoken way, a chemical reaction. To determine i f the students' inclusion of need in their responses is teleological thinking or just teleological writing however, would require further investigation. Interestingly items 14 and 1 from the Henry Survey and the Bishop and Anderson Survey respectively, showed the highest degree of post unit usage of scientific conceptions as well as the highest degree of increase in usage of scientific conceptions. I have classified the conceptual changes based on these items as successful earlier on in 104 this chapter. Both these items however, also show the highest degree of teleological thinking. Perhaps this is confirmation that new alternative conceptions are inevitable, and conceptual change, is accompanied by development of new alternative conceptions. As stated previously, the evolution unit was developed to increase the usage of the scientific conceptions. Perhaps it needs to be expected that new hybrid conceptions will arise as students try to incorporate new knowledge into current understandings. The goal of this previous section was to identify the new conceptions that emerged so that instructors, or anyone interested in teaching a unit of the kind described here, may be made aware of the potential for students forming new hybrid conceptions. This might allow the teacher to help students correct for these hybridized understandings if they are being generated during the course. 105 CHAPTER SEVEN SUMMARY AND CONCLUSION In this chapter I present a summary of my research which looked at determining students pre-instructional conceptions about evolutionary biology, and investigated whether a conceptual change Evolutionary Biology Unit would be successful at increasing students' use of scientific conceptions in their explanations of evolutionary phenomenon after. I then present my conclusions from this study, and look at the implications this study may have for instruction in evolutionary biology. I present my conclusions that emerged from my analysis of data pertaining to research question #1, then move on to conclusions associated with research question #2. Finally I will discuss areas for future research, and offer ideas for future studies that seem to be logical outgrowths of this study. This study was designed to investigate two research questions: 1. What is the range of conceptions held by grade 11 Canadian high school students regarding evolutionary biology, and evolutionary theory? 2. Can teaching an Evolutionary Biology unit, based on conceptual change instructional approaches, help students negotiate conceptual change and acquire scientific conceptions regarding evolutionary theory? Summary To answer the research questions I conducted a study of Grade 11 Biology students in a suburban high school in British Columbia. My class of 30 students was 106 surveyed via questionnaires to assess their conceptions of Evolutionary Biology. Two instruments were used, the Henry Survey, and the Bishop and Anderson Survey. Students completed the surveys at the start of the study to determine their entering conceptions. I then taught a unit on Evolutionary Biology based on a conceptual change approach derived from the model described by Posner et al (1986). At the end of the unit students completed the two surveys again. This time the results were used to assess whether or not this Evolutionary Biology unit I taught was successful at increasing students' usage of scientific conceptions. Overall this unit appeared to be successful at increasing students' usage of scientific conceptions. Student responses to 9 of the 10 survey items on the Henry Survey showed a post-unit increase in usage of scientific conceptions. Student use of scientific conceptions was found to increase on 5 of the 8 Bishop and Anderson Survey items. Overall, I found that by explicitly presenting students with scientific conceptions, by teaching students the vocabulary they needed to differentiate alternative conceptions from scientific conceptions, and by directly comparing scientific conceptions with the alternative conceptions, students were able to increase their usage of scientific conceptions in their explanations for evolutionary biology. In the next section of this chapter I discuss conclusions specific to each of my research questions. 107 Conclusions from Research Question #1: What Is The Range Of Conceptions Held By Grade 11 Canadian High School Students Regarding Evolutionary Biology, And Evolutionary Theory? Conclusion #1: Students enter biology class with a diverse range of conceptions about evolutionary biology. Students entered my Biology class with a variety of conceptions, both scientific and alternative, about biological evolution, not just regarding evolutionary theory, but also regarding the nature of science itself. The majority of their conceptions were alternative conceptions. This is consistent with previous research (Bishop & Anderson, 1990; Demastes, Settlage, & Good, 1995; Jenson & Findley, 1995). Students also began the Evolution unit with some scientific conceptions. These scientific conceptions did not noticeably change over the course of the unit. First, students held the scientific conception that evolutionary theory is legitimate science. Second, they thought that evolution did not have to be directly observed in order to provide scientific explanations. Third they could see the implication of studying and understanding evolution because this knowledge had implication for human health (i.e. bacteria can and do evolve and develop resistance to antibiotics). The basis and origin of students' prior scientific knowledge was not part of this study. However given that I taught about bacteria developing antibiotic resistance through mutations in a Microbiology unit, and taught about the hypothesis of common descent in a unit on Unity 108 and Diversity, it is possible and likely that some students developed their scientific conceptions of evolution through these experiences. Conclusion #2: The range of alternative conceptions appears to be diverse but finite. I found that the range of students' alternative conceptions on a particular topic was diverse, but not infinite; this is consistent with previous research (e.g. Wandersee et al. 1994). A number of popular alternative conceptions were evident in the data. For example I found that students' conceptions were very Lamarckian, in that students thought that organisms developed or lost traits through use or disuse of these trait, and further thought that new altered traits acquired (or lost) through use and disuse could be passed on to subsequent generations. I also found that students' explanations were very teleological, in that many thought that organisms change to satisfy some need or purpose. These types of conceptions have all been reported by other researchers (Bishop & Anderson, 1990; Brumby, 1984; Demastes, Good, & Peebles, 1995; Demastes, Settlage, & Good, 1995; Jenson & Findley, 1995). The finite number of alternative conceptions makes it feasible to design a unit to affect conceptual change. In studying the impact of the unit, seven categories of conceptions were examined using the two survey instruments, the Henry Survey and the Bishop and Anderson Survey. For all categories save one, students held alternative conceptions. The categorization proved to be a useful tool for analyzing students' thinking about evolution. 109 Conclusions from Research Question #2: Can Teaching An Evolutionary Biology Unit, Based On Conceptual Change Instructional Approaches, Help Students Negotiate Conceptual Change And Acquire Scientific Conceptions Regarding Evolutionary Theory? Conclusion #1: Conceptual change instruction can assist students in acquiring scientific conceptions. This study suggested that a conceptual change approach based on the Posner et al. model was helpful in getting students to increase their use of scientific conceptions in their explanations for evolutionary biology phenomenon. Students' use of scientific conceptions increased for all of the conception categories identified in the unit except one (conceptions about the nature of science). Conclusion #2: While a range of conceptual change strategies can be used for promoting scientific understanding of evolution, one of the most successful strategies is to make explicit the difference between scientific and alternative conceptions. Among the range of strategies used, the one that appeared to be most successful was to make explicit the different conceptions, scientific vs. alternative, to the student. When instruction explicitly differentiated the scientific from the alternative conceptions, the post unit increase in scientific conception use was large, indicating that conceptual change was relatively easy to make. When instruction was not explicit, the change was smaller and appeared more difficult to make. 110 In some cases, being explicit was a case of directly telling students what the scientific conception actually was. Three of the largest increases in scientific conception usage resulted from doing just that. For example, to promote understanding of the concept of common ancestry, students were told that humans and monkeys share common ancestry, and that humans did not evolve from modern day monkeys. Modern day monkeys are evolutionarily as far away from the ancestral common ancestor as humans are. They were presented with activities to reinforce that conception, and given examples where the alternative conception proves dissatisfying (e.g. they should not expect to see any modern day monkeys transitioning into humans). In a second case, to promote understanding of the concept of adaptive change, students were given explicit instruction on how natural selection contributes to adaptive change. They were presented with activities to reinforce that conception, and given examples where the alternative conception could not explain the event (e.g. i f you cut off the tail of mice generation after generation, the offspring mice do not have shorter tails). Conclusion #3: Distinguishing between scientific and everyday meanings of terms appears to be important in promoting conceptual change with respect to understanding of evolutionary biology. Another approach that appeared to be successful at promoting understanding of scientific conceptions was the approach of introducing students to the science vocabulary in the correct science context, and the lay vocabulary in the lay context. By alerting students to the two contexts, and presenting the vocabulary to go with each context, I l l students appeared to understand that different conceptions were appropriate for different domains. Through practice they seemed able to use the conceptions in the domains that they were intended for, and switch back and forth when appropriate. This may have contributed to the increase in their usage of the scientific conception. Students who are aware that different domains of knowledge often share common elements of terminology, and who switch at appropriate times perform better than students who do not (Wandersee et al. 1994). Increases in the usage of scientific conceptions on the Henry Survey, for item 3 (evolution vs. origin of life), item 4 (metaphysics based belief, vs. evidence based belief), and item 7 (theory vs. law) may have been influenced by my providing students with appropriate vocabulary. The idea of the teacher being explicit and differentiating concepts is in line with the Posner et al. (1982) model which suggests that the student must be made aware that their alternative ideas are anomalous. If students do not recognize their conceptions are insufficient to explain observed reality, they will have no impetus to seek, or accept different and potentially more fruitful conceptions. The findings from my study suggests that explicit presentation of the scientific conception and differentiating concepts through appropriate use of vocabulary is an effective strategy for promoting students increased usage of scientific conceptions. 112 Conclusion #4: Conceptual change instruction has its limits. Certain conceptions are particularly resistant to change. I found that students' conceptions concerning the nature of science are among the most difficult conceptions to change. This is in line with findings of The National Academy of Sciences (1998), which has identified nature of science concepts as an area where students of Biology hold resistant alternative conceptions. In my study, I taught students about the nature of science at the beginning of the academic year, but made no explicit mention of, or connection with, the topic of Evolutionary Biology. After participating in the Evolution unit, where we used scientific methods (hypothesis testing); students' scientific conceptions about the nature of science were diminished rather than enhanced. It may be that in order to affect an increase in the students' use of scientific conceptions, discussions of the nature of science must be explicitly tied to evolutionary theory. My findings also indicate that conceptions stemming from teleological reasoning are difficult to change. After explicit instruction in Lamarckian verses Darwinian mechanisms, some students still held on to the conception that organisms change because they need to change. They presented explanations for evolutionary change using hybrid conceptions of need plus selection. Teleological thinking appears to persevere through acquisition of scientific conceptions to become incorporated into new student conceptions. This study indicated that explicitly differentiating the scientific and alternative conceptions through the usage of appropriate vocabulary was successful in helping 113 students negotiate conceptual change in other areas. Perhaps explicit instruction about teleological thinking may help students move from their teleological based explanations towards more scientific based explanations. That is, rather than just presenting the difference between Darwin and Lamarckian theory, as far as mechanism goes, the teacher may need to differentiate between the teleological basis for Lamarckian mechanisms of evolution, and the non-teleological basis for Darwinian mechanisms of evolution. By explicating the teleology inherent in one theory as opposed to the other, students may be able to recognize and differentiate teleology from non-teleology in their reasoning, and perhaps learn to identify and avoid it in their writing. Teleological thinking appears to be compelling and appealing to students. On certain items, students changed from a "teleological Lamarckian" explanation to a "teleological Darwinian" explanation. Conceptions regarding nature of science, and teleology may benefit from more direct and explicit treatment of the scientific and alternative conceptions. My unit as taught did not do this. Considerations of the nature of science or teleology were not a central aspect of my unit design, they were definitely more peripheral. I think i f this study were being extended it would be beneficial to have a more directed focus on students' conceptions about the nature of science and teleological thinking. Survey Item Redesign for the Henry Survey Based on the responses I received, there were some survey items that did not isolate the conception that I was trying to elicit and inspect. These items need to be 114 reworded. In this section I offer comment on these items and suggest possible rewordings or replacement items for future surveys. 115 Change To Item #1 on the Henry Survey Item #1 reads "According to the theory of evolution, humans evolved from monkeys." This item is intended to elicit student's conceptions about the distinction between ancestral primates and present day primates. That is, you should not expect to see monkeys turning into humans today. Based on my analysis of students' responses, this item could have been clearer. I would change the item to ask "If humans descended from monkeys, why don't we see any monkeys turning into humans today?" I think this is a more straightforward item that probes the same alternative conception, and can be dealt with in the same way. That is, by pointing out that the theory of evolution does not say we emerged from modern day monkeys, it says we came from ancestral primates. Humans and monkeys descended from common ancestors, and we are as far away from that ancestor as today's modern monkeys are. Change to Item #12 on the Henry Survey The Henry Survey item 12 reads "Evolution theory is used to cure cancer." The intent of this item was to see i f students appreciated that evolutionary theory had practical applications in different fields of biology. I think however, that this item was poorly worded, leading students to misinterpret it. As I mentioned previously, I don't think this item served its intended purpose. The reason is the term cancer actually encompasses a number of different diseases, and currently there is no known cure for cancer. If students read the item as saying that evolutionary theory cures cancer, rather than it informs research into curing cancer, they would be correct in stating that evolutionary theory doesn't really cure cancer. Item 12 should be changed to read "Evolutionary theory is used in cancer research." This is more straightforward. It elicits the students' conception 116 about the practical applicability of evolutionary theory to cancer research, but it removes the implication that evolutionary theory cures cancer. Change to Item #13 on the Henry Survey Item 13 on the Henry Survey reads "The word disproof is more valid in science than the word proof." I wanted to distinguish the concept of proving hypotheses, from the concept of disproving hypotheses, and reveal students' ideas about the concept of falsification in science. This item did not do that. Item 13 should be changed to read "What is the role of proof and disproof in hypothesis testing?" This makes the item more open ended, but more direct; and allows students now to give a more direct answer. Areas for Future Research Nature of Science and Scientific Method Students appear to hold alternative conceptions about the nature of science that are very persistent. For example, lay conceptions about the word theory and its explanatory power in science (as being a speculation, or little more than a hypothesis) persisted through the unit. Students require more in depth and explicit instruction on the nature of science than they have received in my course. These findings are in line with The National Academy of Sciences (1998) who found alternative conceptions about the nature of science persist in students and are one of the hurdles affecting scientific literacy in general, and understanding of evolutionary theory in particular. M y study finding suggests that a conceptual change unit explicitly dealing with nature of science conceptions may be necessary if we wish to help students increase their usage of 117 scientific conceptions in this area. Further, by discussing nature of science concepts in an evolutionary biology context (or using evolutionary biology examples), students may have more success increasing their usage of scientific conceptions of evolutionary biology when they get to the topic of evolutionary biology. Teacher Education It would be very interesting to continue and extend this study with a focus on the teachers. Since alternative conceptions persist i f not addressed, people carry these conceptions into adulthood. I think that another group to study in order to answer the research questions posed in this study would be biology teachers themselves. For research question #1, it would simply be a matter of presenting both surveys used in this study to teachers to see what their current conceptions are; and to compare their conceptions with those of students entering Biology 11. I think it would be particularly interesting to examine teacher conceptions and personal definitions of theory, law, and evidence, and their views on how the word belief is used in science. Research question #2 however would be more difficult to extend to teachers as it would require a group of teachers to actually take the Biology 11 unit. Still I think feedback from teachers would be very instructive and could improve the presentations of evolutionary theory in my course. There were, and probably still are, some items on the Henry Survey that needed rewording, and there are undoubtedly other areas of the unit that need reevaluation. A focus group of teachers could provide feedback that would be invaluable in that regard. 118 Curriculum and Learning Resources Design One final area for future study is in designing curriculum and learning resources. If this study has indeed.been able to identify the typical categories of alternative conceptions held by Biology 11 students (more study would need to be done to confirm that these conceptions are typical), then curriculum and learning resources can be designed based on these alternative conception categories. Curriculum can be designed with a focus on increasing student's usage of the scientific conceptions hindered by these alternative conceptions. The curriculum and resources can be tested against student populations, using the surveys as measurement tools, to see i f scientific conception usage increases when these new curricula or resources are implemented. 119 References American Association for the Advancement of Science. (1993). Benchmarks for science literacy. Retrieved July 25, 2005 from http://www.proi ect2061 •org/tools/benchol/bolframe.htm. BC Ministry of Education (1996). Retrieved July 25, 2005 from http://www.bced.gov.bc.ca/irp/biology/bil 1 .htm. Bishop, B., & Anderson, C. (1990). Student conceptions of natural selection and its role in evolution. Journal of Research in Science Teaching, 27(5): 415-427. Bishop, B.A.; Anderson, C W . (1986). Evolution by natural selection: a teaching module (Occasional Paper No. 91). East Lansing, MI: Institute for Research on Teaching, Michigan State University. Brumby, M . (1984). Misconceptions about the concept of natural selection by medical biology students. Science Education, 68(4): 493-503. Demastes, S. S., Good, R. G., Peebles, P. (1995). Students' conceptual ecologies and the process of conceptual change in evolution. Science Education, 79(6): 637-666. Demastes, S., Settlage, J., & Good, R. (1995). Students' conceptions of natural selection and its role in evolution: cases of replication and comparison. Journal of Research in Science Teaching, 32(5): 535-550. Dobzhansky, T. (1973). Nothing in biology makes sense except in the light of evolution. The American Biology Teacher, 35(3), 125-129. Duit, R. and Treagust, D. (1998). Learning in Science - From Behaviourism Towards Social Constructivism and Beyond. In B.B. Fraser andK.G. Tobin Eds., International Handbook of Science Education 3-25 Kluwer. Evolution, Science, and Society White Paper. (2000). Retrieved July 25, 2005 from http://www.rci.rutRers.edu/~ecolevol/fulldoc.pdf. Fisher, K . M . , Becvar, L, Gomes, S. et al., San Diego State University (1997). Retrieved July 25, 2005 from http://www.biologylessons.sdsu.edu/ Jensen, M . S., and Finley, F. N . (1995). Teaching evolution using historical arguments in a conceptual change strategy. Science Education, 79(2): 147-166. Mader, S. (1997). Inquiry into Life (8th ed). Boston: McGraw-Hill Mintzes, J. J., Arnaudin, M . W. (1984). Children's Biology: A review of research on conceptual development in the life sciences. Wilmington, North Carolina: North Carolina University at Wilmington, Department of Biological Sciences. National Academy of Sciences. (1998). Retrieved July 25, 2005 from http://www.nap.edii/readingroom/books/evolution98/contents.html National Research Council. (1996). Retrieved July 25, 2005 from http://books.nap.edu/html/nses/html/index.html. Palumbi, S. (2002, July) A theory evolves U.S. News and World Report 29 July 2002. 121 Posner, G.J., Strike, K . A . , Hewson, P. W., & Gertzog, W.A. (1982). Accommodation of a scientific conception: toward a theory of conceptual change. Science Education, 66(2): 211-227. Ritter, B., Coombs, R. F., & Drysdale, B. (1996). Nelson Biology (British Columbia ed.). Scarborough: Nelson Canada. Sinatra, G. M . , Southerland, S. A. , McConaughy, F., Demastes, J. W. (2003). Intentions and beliefs in students' understanding and acceptance of biological evolution. Journal of Research in Science Teaching, 40(5): 510-528. Smith, M . U . (1994). Counterpoint: belief, understanding, and the teaching of evolution [Special issue]. Journal of Science Teaching, 31(5): 591-597. Wandersee, J. Mintzes, J. Novak, J. (1994) Research on Alternative Conceptions in Science. In Gabel, D., Ed., NSTA Handbook: Research in Science Teaching, Chapter 5. New York: Macmillan. Wikipedi. (2005). Retrieved July 25, 2005 from http://www.wikipedia.org/wiki/Evolution Poll. Zietsman A. I., and Hewson, P. W. (1980). Effect of instruction using microcomputer simulations and conceptual change strategies on science learning. Journal of Research in Science Teaching, 23(1): 27-39. 123 Confidentiality: 1. A l l data collected will remain confidential through the following procedures • Student's names will not appear on any written documents of the project. In addition any reference to the student's school will remain strictly confidential. • A l l data will be kept in a locked cabinet accessible only by the researchers. Records kept on computer will only be accessed using a special code known only to the researchers. • Parents and students can choose to view the data collected that was produced by the student at any time. 2. There will be no consequence for not participating in this study, or for choosing to withdraw at any time from the study. 3. Only those students who agree to participate, and obtain parental or legal guardian consent, will have their questionnaire and test data included in the analysis portions of this study. 4. Student questionnaires will be placed in a sealed envelope until the end of the course. 5. To assure equitable treatment of all students no data will be examined until after the Biology 11 course is completed at the end of the semester. Procedures: 1. A student volunteer will distribute the questionnaires to you. 2. Please complete the questionnaire in the allotted 25 minutes. 3. When you are finished, please hand your questionnaire to the student volunteer who will place the questionnaires in a manila envelope. When all the questionnaires placed are in the envelope, the student volunteer will seal the envelope. 4. When all the questionnaires are sealed, the volunteer will take the envelope to the office where they will remain in a sealed container away from the instructor until the course is completed. 5. The questionnaire will be rewritten at the end of the unit of study, as per steps 1-4. 124 Biology 11 Evolution, What I know now Name Date Respond to the following statements, and offer a brief explanation for your answer. 1. According to the theory of evolution, man evolved from monkeys. 2. According to the theory of evolution, all organisms are constantly evolving. 3. The theory of biological evolution is used to explain the origin of life. 4. Evolution is a belief held by some scientists but not by all. Use this example to help answer question 5. Lemon Juice pH Baking Soda pH Above is a pH scale, it represents a continuum showing acid and base concentrations. As you move to the left you increase your acid concentration towards 100% and decrease your base concentration towards 0%, as you move to the right you increase your base concentration towards 100% and decrease your acid concentration towards 0%. 125 Lemon juice is highly acidic and slightly basic, it's pH is represented by the vertical line near the left of the continuum. Baking soda on the other hand is highly basic and slightly acidic, it's pH is represented by the vertical line near the right of the continuum. 5. Using the scale below, please answer the following questions, and offer an explanation for your answer. a) Where would the phrase "Explanations for the origin of man" fall on the continuum below (draw a vertical line to represent your choice) Explanation: b) Does evolution offer an explanation for the origin of man? Explain. c) Where would you put the word Evolution on the continuum below (draw a vertical line to represent your choice) Religion Explanation: 6. The theory of evolution has some holes in it. If organisms were evolving, you would still be able to see them evolving today, and you don't. 7. If evolution were true it would be a law not just a theory. 126 8. Evolution is incompatible with religion. 9. The theory of evolution is not testable, because the only way to do that would be to go back into time and actually watch the animals as they change, and there is no way you can do that. 10. Small populations evolve faster than large populations because in small populations it's easier to lose genes. 11. Bacteria are evolving resistance to antibiotics faster than we can create new antibiotics to kill them. 12. Evolution theory is used to cure cancer. 13. The word disproof is more valid in science than the word proof. 14. The fossil record shows that the ancestors of giraffes did not have long necks. Formulate an explanation for how you think giraffes got their long necks. 127 Once you've got your answer written down, form your group, and come to a consensus as how giraffes got their long necks. 128 Appendix 8 Bishop and Anderson Survey Biology 11 Evolution, What I know now pt.2 Name Date 1. Cheetahs (large African cats) are able to run faster than 60 miles per hour when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could only run 20 miles per hour? 2. Cave salamanders are blind (they have eyes which are nonfunctional). How would a biologist explain how blind cave salamanders evolved from sighted ancestors? 129 3. For the following question, use the numbered statements listed and circle the number which most closely corresponds to what you understand. 1 - The statement on the left is the only correct statement. 2- The statement on the left is more correct. 3- Both statements are equally correct. 4- The statement on the right is more correct. 5- The statement on the right is the only correct statement. If neither statement represents your understanding, please explain. Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists explain that ducks evolved from land birds which did not have webbed feet. a. The trait of webbed feet in ducks: Appeared in ancestral ducks because they lived in water and needed webbed feet to swim. 1 2 3 4 5 Appeared in ducks because of a chance mutation. Explain: b. While ducks were evolving webbed feet: With each generation, most ducks had about the same amount of webbing on their feet as their parents. 1 2 3 4 5 With each generation most ducks had a tiny bit more webbing on their feet than their parents. Explain: c. If a population of ducks were forced to live in an environment where water for swimming was not available: Many ducks would die because their feet were poorly adapted to this environment. 1 2 3 4 5 The ducks would gradually develop nonwebbed feet. Explain: d. The population of ducks evolved webbed feet because: The more successful ducks adapted to their aquatic environment. 1 23 4 5 The less successful ducks died without offspring. Explain: 130 4. A number of mosquito populations are today resistant to DDT, even though those species were not resistant to DDT when it was first introduced. Biologists would explain that DDT resistance evolved in mosquitos because: (choose the best answer) a. Individual mosquitos built up an immunity to DDT after being exposed to it. b. Mosquitos needed to be resistant to DDT in order to survive. c. A few mosquitos were probably resistant to DDT before it was ever used. d. Mosquitos learned to adapt to their environment. e. Other; please explain 5. Biologists often use the term "fitness" when speaking of evolution. Below are descriptions of four male lions. According to your understanding of evolution, which lion would biologists consider the "fittest"? Name George Ben Spot Sandy Size 10 feet/1751bs 8 feet/160 lbs 9 feet/162 lbs 9feet/160 lbs Number of 19 25 20 20 cubs fathered Age of death 13 years 16 years 12 years 9 years Number of 15 14 14 19 cubs surviving to adulthood Comments George is very Ben has the When the area Sandy was large, very greatest number that Spot lived killed by an healthy. The of females in in was infection strongest lion. his harem. destroyed by fire, Spot was able to move his pride to a new area & change his feeding habits. resulting from a cut on his foot. The "fittest" lion is: a. George b. Ben c. Spot d. Sandy Explain your answer: Appendix C Comparison of Pre and Post Unit Conceptions for Henry and Bishop and Anderson Survey Comparison of Pre and Post Unit Conceptions for Henry Survey Item 1: According to the theory of evolution, man evolved from monkeys. Scientific Conception: Humans and monkeys descended from common ancestors, humans did not evolve from modern day monkeys. A distinction exists between modern day monkeys and ancestral monkey-like primates. Table CI Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28) Scientific Conception Revealed (SC): SC - Humans evolved from apes or some ancestral primate, humans did not evolve from monkeys. (4) Scientific Conception Revealed (SC): SC -Humans and monkeys descended from common ancestors, humans did not evolve from monkeys. (26) Alternative Conceptions Revealed (AC): AC1 -Humans descended from monkeys, no distinction is made between modern day monkeys and ancestral monkey-like primates. (23) AC2 -Humans did not descend from pre human ancestors, evolution of humans did not occur. (1) Alternative Conceptions Revealed (AC): AC1 -Humans descended from monkeys. (2) AC2 - None 131 SC Man and monkey descended form AC1 Man descended from monkey, no AC2 -Man did not descend from pre common ancestors, man did not distinction is made between modern human ancestors, descend from monkey. day monkey and ancestral monkey-like primates. Figure 1. Comparison of detailed pre unit and post unit conceptions Item 2: According to the theory of evolution, all organisms are constantly evolving. Scientific Conception: Population change, as a result of environmental change, can stabilize in a constant (static) environment. Table C2 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=28) Post Unit Conceptions (n=27) Post Unit Conceptions That Compare With Pre Unit Conceptions New Post Unit Alternative Conceptions Scientific Conception Revealed (SC): SC 1 - Change is caused by environmental pressures. In the absence of these pressures, there is no change. (0) SC 2 -Not all organisms evolve all the time, some organisms don't change. (1) SC 3 -Change is caused when one of the factors that violates Hardy Weinberg equilibrium occurs. (0) SC 4 - Not all organisms are evolving, they are adapting. This student reasons that evolution and adaptation are different processes. (0) Scientific Conception Revealed (SC): SC 1 - Change is caused by environmental pressures. In the absence of these pressures, there is no change. (2) SC 2 - Not all organisms evolve all the time, some organisms don't change. (2) SC 3 -Change is caused when one of the factors that violates Hardy Weinberg equilibrium occurs. (3) SC 4 - Not all organisms are evolving, they are adapting. This student reasons that evolution and adaptation are different processes. (1) Alternative Conceptions Revealed (AC): (Total=27) A C 1-Organisms are constantly changing to keep up with a constantly changing environment. (16) A C 2-Organisms change because of genetic recombination (offspring Alternative Conceptions Revealed (AC): A C 1- Organisms are constantly changing to keep up with a constantly changing environment. (2) AC 2- Organisms change because of genetic recombination (1) New Alternative Conceptions Revealed (NAC): N A C 1- Organisms are no longer evolving, so not all organisms change. This student appears to be under the impression that evolution has ceased. (1) N A C 2- Some organisms don't need to 133 different than parent). (3) A C 3-Organisms change because evolution is goal directed, and we'll keep evolving until we get there. (1) A C 4-Organisms are always changing. (6) A C 5-The concept of organisms evolving is wrong. (1) A C 3-Organisms change because evolution is goal directed (1) A C 4 -Organisms are always changing. (9) A C 5-The concept of organisms evolving is wrong. (0) change, so not all organisms change. This is a combination of Lamarckian and Darwinian conceptions. (2) N A C 3- A l l organisms change due to the factors that violate Hardy Weinberg. (3) No Response Recorded: (1) 134 Figure 2. Comparison of pre unit and post unit conceptions g n o 3 ta 5. c/a O S3 O >-h a-rc r 4 (T a-5 6 a. •a o 6 3 o 3 o 5" 3 SC1 Change is caused by environmental pressures... SC3 Change is caused when... violates Hardy Weinberg. AC1 Organisms are constantly evolving to keep up with a constantly AC 3 Organisms change because evolution is AC5 The concept of organisms evolving is wrong. ON Item 3: The theory of biological evolution is used to explain the origin of life. Scientific Conception: Theories of evolution explain the causes of evolution, how life changes. Theories of origin of life explain how life began. Table C3 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=20) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=24) Scientific Conception Revealed (SC): -Theory of evolution explains how life changed, not how life started. (1) Scientific Conception Revealed (SC): -Theory of evolution explains how life changed, not how life started. (9) Alternative Conceptions Revealed (AC): -The theory of evolution is used to explain the origin of life. (19) Alternative Conceptions Revealed (AC): -The theory of evolution is used to explain the origin of life. (15) No Response Recorded: (8) No Response Recorded: (4) 137 Figure 4. Comparison of pre unit and post unit conceptions Item 4: Evolution is a belief held by some scientists but not by all. Scientific Conception: Statements of belief acquired from the scientific process are based on evidence rather than faith. Statements of belief acquired while investigating evolution are based on evidence for evolution, rather than faith in evolution. Table C4 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=21) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=25) Scientific Conception Revealed (SC): (4) Belief in evolution is based on evidence not faith: -Some scientists want more proof (these students see evolution as an evidence based belief) (3) - A l l scientists believe that evolution exists because the facts are there. (1) Scientific Conception Revealed (SC): (11) -Belief in evolution is based on evidence not faith. (11) Alternative Conceptions Revealed (AC): (17) Belief in evolution is faith based (metaphysical belief): -Evolution is a belief, and we all have our own opinions/theories. (10) -Some people don't believe in evolution, some believe in God/religion. (7) Alternative Conceptions Revealed (AC): (14) - Belief in evolution is faith based (metaphysical belief): -Evolution is a belief, and we all have our own opinions/theories. (7) -Some people don't believe in evolution, some believe in God/religion. (7) No Response Recorded: (7) No Response Recorded: (3) 139 HPre Unit Totals • Post Unit Totals SC Belief in evolution is based on AC1 Evolution is a belief, and we all AC2 Some people don't believe in evidence not faith. have our own opinions/theories. evolution, some believe in God/religion. Figure 6. Comparison of detailed pre unit and post unit conceptions 141 Item 5 a): Where would the phrase "Explanations for the origin of man" fall on the continuum below (draw a vertical line to represent your choice)? Table C5a Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=26) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28) Conceptions Revealed: -Science explains origin of humans more so than religion. (10) -The explanations for the origin of humans offered by science hold as much significance as the explanations offered by religion. (14) -Religion explains origin of humans more so than science. (2) Conceptions Revealed: -Science explains origin of humans more so than religion. (8) -The explanations for the origin of humans offered by science hold as much significance as the explanations offered by religion. (17) - Explanations for the origin of humans are mostly religious. (3) No Response Recorded: (2) aThis question is not an alternative conceptions probe, therefore no pre post comparison made. Item 5 b): Does evolution offer an explanation for the origin of man? Explain. Table C5b Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=27) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=26) Conceptions Revealed: SCI -Evolution does offer an explanation for the origin of humans; it says we evolved form earlier life forms Conceptions Revealed: SCI -Evolution does offer an explanation for the origin of humans; it says we evolved form earlier life forms 142 (monkeys/apes). (18) SC2 -Evolution does offer an explanation for the origin of humans, the evidence is there for us to examine. (2) SC3 -Evolution offers possible/plausible explanations, but doesn't offer step by step scenarios. (2) SC4 -Evolution offers possible/plausible explanations, and gives a detailed explanation as well. (1) SC5 -Evolution offers explanations because we know how things began. (1) SC6 -Agreement that evolution offers explanations, but with no further elaboration. (1) AC1 -Maybe, It's only a theory. (1) A C 2 -Maybe, it isn't necessarily right. (1) (monkeys/apes). (7) SC7 -Evolution does offer an explanation for the origin of humans; it offers an explanation of how we became what we are today. (5) SC8 -Evolution does offer an explanation for the origin of humans; It explains how the body evolved, but says nothing about the soul. (1) SC6 -Evolution does offer an explanation for the origin of humans; (Agree -With no further elaboration). (1) SC3 -It offers possible/plausible explanations, but doesn't offer step by step scenarios. (5) SC9 -Disagree, evolution offers explanations for the proximate descent of humans, not the ultimate origin of humans. (6) AC1 -Evolution is just a theory: (n=l) No Response Recorded: (1) No Response Recorded: (2) bThis question is not an alternative conceptions probe, therefore no pre post comparison made. Item 5 c): Where would you put the word Evolution on the continuum below (draw a vertical line to represent your choice)? Scientific Conception: Evolution is science. Table C5c Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=25) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=27) Scientific Conceptions Revealed (SC): -Evolution is Science. (24) Scientific Conceptions Revealed (SC): -Evolution is Science. (27) Alternative Conceptions Revealed (AC): Alternative Conceptions Revealed (AC): 143 -Evolution isn't total science. (1) None No Response Recorded: (3) No Response Recorded: (1) 120% O Pre Unit Totals • Post Unit Totals SC Evolution is science. AC Evolution is not science. Figure 7. Comparison of pre unit and post unit conceptions 144 Item 6: The theory of evolution has some holes in it. If organisms were evolving, you would still be able to see them evolving today, and you don't. Scientific Conception: Rates of evolutionary change are observable and calculable in the present day; and hypotheses of common descent can be tested to arrive at conclusions about evolutionary change in the past. We do not have to directly observe a process to explain how that process occurs. Table C6 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=27) Post Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions New Post Unit Alternative Conceptions Scientific Conceptions Revealed (SC): (Two students overlapped categories for this question) - We don't see organisms evolving today because organisms take a long time to evolve (geological time). (22[2 students overlap with the category below]) - We don't see organisms evolving today because organisms change when the environment changes, currently there are no great environmental changes. (3[2 students overlap with the category above]) -We don't see organisms evolving today because the changes are very small. (2) Scientific Conceptions Revealed (SC): (Four students overlapped categories on this question) - We don't see organisms evolving today because organisms take a long time to evolve (geological time). (22 [3 students overlap with the category 2, and 1 student overlapped with category 3]) -We don't see organisms evolving today because organisms change when the environment changes, currently there are no great environmental changes. -The organism has already adapted to their environment and there is no pressure for change (stabilizing selection). (4[3 students overlap with category 1 above]) 145 - Evolution does occur today. You see it whenever you observe change in allele frequency. (3 [1 student overlapped with category 1]) - We are only able to see large scale evolution. (1) Alternative Conceptions Revealed (AC): -Evolution does have some holes in it/there is something wrong with the theory of evolution. (2) Alternative Conceptions Revealed (AC): -None (0) New Alternative Conceptions Revealed (AC): - Evolution only occurs when there is a new organism. (1) No Response Recorded: (1) 146 II Pre Unit Totals • Post Unit Totals SC Rates of evolutionary change are AC If organisms were evolving you NAC Evolution only, occur,«whe there is S^ZZZ^JZf would still be able to see them evolving a new organism common descent can be tested. today, and you don t. Figure 8. Comparison of pre unit and post unit conceptions 147 Item 7: If evolution were true it would be a law not just a theory. Scientific Conception: Laws are descriptions; theories are explanations. Law is not a stronger word for certainty than theory. Laws are not proven theories; theories do not become laws once they become proven. Table C7 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=26) Post Unit Conceptions (n=26) Post Unit Conceptions That Compare With Pre Unit Conceptions New Post Unit Alternative Conceptions Scientific Conceptions Revealed (SC): None of the students' responses on this item were consistent with the scientific conception. A theory and a law are two different things. A theory is an explanation, a law is a description. A theory does not become a law. (0) Scientific Conceptions Revealed (SC): (One student overlapped categories on this question) A theory and a law are two different things. A theory is an explanation, a law is a description. A theory does not become a law. (12) Alternative Conceptions Revealed (AC): AC1 -If evolution were true/proven, it would be a law by now (law is a proven theory). (15) AC2 -Evolution is not proven because of the nature of evolution being unobservable, it can't be proven. (3) AC3 -Evolution is not a law because it has some problems (holes in the theory). (2) AC4 -Evolution is not proven because of the nature of proof, it's impossible to know Alternative Conceptions Revealed (AC): AC1 -If evolution were true/proven, it would be a law by now (law is a proven theory). (9) AC2 -Evolution is not proven because of the nature of evolution being unobservable, it can't be proven. (2) AC3 -Evolution is not a law because it has some problems (holes in the theory). (2) New Alternative Conceptions Revealed (NAC): -A theory is better than a law. (1) 148 anything 100% so a theory is the best we can call it. (3) AC5 -Evolution should be a law, the evidence is overwhelming. (2) AC6 -Denial that evolution is a reality. (1) No Response Recorded: (2) No Response Recorded: (2) 149 120% 100% 100% 80% 4— 60% 4 40% 20% 0% 46% 0% HPre Unit Totals • Post Unit Totals SC A theory and a law are two different things. A theory is AC Law is a stronger word for certainty than theory, an explanation, a law is a description. A theory does not become a law. Figure 9. Comparison of pre unit and post unit conceptions 150 70% 60% 50% 40% 30% | 20% 10% 0% -68%" -48%-0% 36% 12% 12% 18% 8% 8% _Ln_LT] o% 4% 0% 0% HPre Unit Totals • Post Unit Totals SC A theory and AC1 If evolution AC2 Evolution is AC3 Evolution AC4 Evolution is AC5 Evolution AC6 Denial that a law are were true it not proven has some not proven should be a law, evolution is a different, a would be a law because of the holes/problems, because of the the evidence is reality, theory does not by now. nature of nature of proof, overwhelming, become a law. evolution. Figure 10. Comparison of detailed pre unit and post unit conceptions 151 Item 8: Evolution is incompatible with religion. Scientific Conception: "Most religions of the world do not have any direct conflict with the idea of evolution." National Academy of Sciences (1998) Table C8 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=21) Post Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions New Post Unit Alternative Conceptions Scientific Conceptions Revealed (SC): SCI -Evolution is not incompatible with religion, both evolution and religion are equally important. (4) SC2 -Evolution is not incompatible with religion, evolution has no religious implications; it simply says that life changes constantly. (1) SC3 -Evolution is not incompatible with religion; science and religion are two separate spheres, which need not overlap or conflict. (1) Scientific Conceptions Revealed (SC): SCI -Evolution is not incompatible with religion, both evolution and religion are equally important. Religious organizations accept evolution. (11) SC2 -Evolution is not incompatible with religion, no explanation provided. (1) SC3 -Evolution is not incompatible with religion; the two are non-overlapping explanations (the two should be kept separate). (5) Alternative Conceptions Revealed (AC): AC1 -Evolution is incompatible with religion; religion has its own set of beliefs that are separate/different from evolution. (4) AC2 -Evolution is incompatible with Alternative Conceptions Revealed (AC): AC1 - Evolution is incompatible with religion; the two are non-overlapping explanations (the two should be kept separate). (3) AC2 -Evolution and religion are New Alternative Conceptions Revealed (NAC): -Evolution and religion are not incompatible because religion talks about origin of life, and evolution doesn't. (1) 152 religion; evolution causes religions to change their beliefs. (1) AC3 -Evolution is incompatible with religion, religion relies on belief in God/a higher power (evolution, and creation by God are mutually exclusive concepts). (5) AC4 -Evolution is incompatible with religion with no further explanation (3) A C 5 - Evolution is incompatible with religion, both are beliefs, and some people believe in evolution like other people believe in religion. (2) incompatible because evolution causes religions to change their beliefs. (1) A C 3 -Evolution is incompatible with religion; religion relies on belief in God/a higher power. (3) AC4 -Evolution is incompatible with religion with no further explanation (2) AC5 -Evolution is incompatible with religion, both are beliefs. (1) No Response Recorded: (7) 153 80% 71% 70% 60% 50% 40% 30% 20% H 10% J 0% 63% ..23%. I Pre Unit Totals I Post Unit Totals SC "Most religions of the world do not have any direct conflict with the idea of evolution." National Academy of Sciences (1998) Figure 11. Comparison of pre unit and post unit conceptions AC Evolution is incompatible with religion. 154 45% i 40% 35% 30% 25°/c I Pre Unit Totals I Post Unit Totals 20% 15% 10% 4-SC1 Evolution SC2 Not SC3 Not AC1 AC2 AC3 AC4 AC5 not incompatible, incompatible, Incompatible, Incompatible, Incompatible, Incompatible, Incompatible, incompatible, evolution they are two they are two because religion no further both are both are simply says non non evolution believes in explanation, metaphysical equally life changes, overlapping overlapping causes God (mutually beliefs, important. explanations, explanations. religions to exclusive change their concepts), beliefs. Figure 12. Comparison of detailed pre unit and post unit conceptions 155 Item 9: The theory of evolution is not testable, because the only way to do that would be to go back into time and actually watch the animals as they change, and there is no way you can do that. Scientific Conception: Testing requires hypothesis formulation and it can be done through experimentation or observation. Testing does not require direct manipulation or perturbation of test subjects. Table C9 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28) Scientific Conceptions Revealed (SC): SCI -Evolution can be tested by collecting data today, and having future generations analyze that collected data. (2) SC2 -Evolution can be tested; the technology (techniques) is available now for us to do that. (1) SC 3-Evolution can be tested by reconstructing past changes through historical evidence (ex the fossil record). 9) SC4 -Evolution can be tested by causing organisms to evolve (microevolution) (2) Scientific Conceptions Revealed (SC): (One student overlapped in categories 3 & 4; I put him in category 4) SCI -Evolution can be tested by collecting data today, and having future generations analyze that collected data. (1) SC2 -Evolution can be tested; the technology (techniques) is available now for us to do that. (0) SC3 -Evolution can be tested by reconstructing past changes through historical evidence (ex the fossil record). (13) SC4 -Evolution can be tested by causing organisms to evolve (microevolution). (8) Alternative Conceptions Revealed (AC): AC1 -Evolution is not testable because we don't have the ability to actually watch the postulated historical changes (We would need a time machine to test evolution). (14) Alternative Conceptions Revealed (AC): AC1 -Evolution is not testable because we don't have the ability to actually watch the postulated historical changes (We would need a time machine to test evolution). (6) 156 90% S C Evolution can be tested. Figure 13. Comparison of pre unit and post unit conceptions 50% • Pre Unit Totals • Post Unit Totals 21% A C Evolution cannot be tested. 60% 50% H 40% 4 30% 20% 10% I Pre Unit Totals I Post Unit Totals SC1 Evolution can be SC2 Evolution can be tested by collecting tested, the technology data today to analyze in exists for us to do that, the distant future. SC3 Evolution can be tested by reconstructing past changes though fossils. SC4 Evolution can be tested by causing organisms to evolve (microevolution). AC1 Evolution cannot be tested because we don't have the ability to watch the postulated changes. Figure 14. Comparison of detailed pre unit and post unit conceptions Item 10: Small populations evolve faster than large populations because in small populations it's easier to lose genes. Table CIO Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=19) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28 Student Conceptions: -Small populations do evolve faster than large populations. The lower the population number, the lower the gene count, and the less likely the chances that any particular gene will make it into the next generation. (6) -Small populations do not evolve faster than large populations; it is actually large populations that evolve faster than small populations. Large populations contain more genes, the more genes, the higher the chances of evolutionary change occurring. (8) -Small populations do not evolve faster than large populations; population size doesn't have an effect on losing genes. (1) -Small populations do not evolve faster than large populations (with no further explanation). (3) -Small populations do not evolve faster than large populations, rates of change are the same regardless of population size, it's just that in small populations with fewer individuals evolution appears faster (1). Student Conceptions: -Small populations do evolve faster than large populations. The lower the population number, the lower the gene count, and the less likely the chances that any particular gene will make it into the next generation. In smaller populations, genes can be more easily removed though breeding (or lack thereof). There is a higher chance that certain genes won't make it into the next generation. (11) -Small populations do evolve faster than large populations. In smaller populations, there is a higher chance of recessives participating as opposed to large populations where recessives are suppressed. (11) -Small populations do evolve faster than large populations (with no further explanation). (5) -Small populations do not evolve faster than large populations (with no further explanation). (1) No Response Recorded: (9) cThis question is not an alternative conceptions probe, therefore no pre post comparison made. 159 Item 11: Bacteria are evolving resistance to antibiotics faster than we can create new antibiotics to kill them. Scientific Conception: Bacteria are evolving resistance to antibiotics; evolutionary theory informs research into bacterial resistance. Table CI 1 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=26) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=27) Scientific Conceptions Revealed (SC): - Bacteria are evolving resistance to antibiotics, evolutionary theory informs research into bacterial resistance (26) Students using a Darwinian mechanism (3) Students using a Lamarckian mechanism (4) Students offering agreement but no mechanism (18) Scientific Conceptions Revealed (SC): - Bacteria are evolving resistance to antibiotics, evolutionary theory informs research into bacterial resistance (27) Students using a Darwinian mechanism (8) Students using a Lamarckian mechanism (2) Students offering agreement but no mechanism (17) Alternative Conceptions Revealed (AC): None Alternative Conceptions Revealed (AC): None No Response Recorded: (2) No Response Recorded: (1) 160 120% 100% 100% SC Bacteria are evolving resistance to antibiotics, evolutionary theory informs research into bacterial resistance. AC Bacteria are not evolving resistance to antibiotics Figure 15. Comparison o f pre unit and post unit conceptions a Pre Unit Totals • Post Unit Totals Item 12: Evolution theory is used to cure cancer. Scientific Conception: Evolution can be used to inform other areas of science, it has practical application (in the area of cancer research for example). Evolutionary theory has applications for cancer research just like it has applications for research into antibiotic resistance in bacteria. Table C12 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=15) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=20) Scientific Conceptions Revealed (SC): - Evolution can be used to inform other areas of science, it has practical application (in the area of cancer research for example). (7) Scientific Conceptions Revealed (SC): - Evolution can be used to inform other areas of science, it has practical application (in the area of cancer research for example). (13) Alternative Conceptions Revealed (AC): -Evolutionary theory does not have practical applications in curing cancer. (8) Alternative Conceptions Revealed (AC): -Evolutionary theory does not have practical applications in curing cancer. (7) No Response Recorded: (13) No Response Recorded: (8) 162 163 Item 13: The word disproof is more valid in science than the word proof. Scientific Conception: "Because hypotheses are always subject to modification, they can never actually be proven true; however, they can be proven false-that is, hypothesis are falsifiable" (Mader p. 12). Table CI3 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=16) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=17) Scientific Conceptions Revealed (SC): -Scientists try to disprove their hypotheses, they do not look for proof (the need for falsifiability exists in science). (5) Scientific Conceptions Revealed (SC): -Scientists try to disprove their hypotheses, they do not look for proof (show need for falsifiability in science). (4) Alternative Conceptions Revealed (AC): AC1 -Proof is more valid than disproof. (2) AC2 -Both words are equally valid (respondents indicate no need for falsifiability in science). (2) AC3 -It's easier to deny/disprove something than to prove it (respondents indicate no need for falsifiability in science). (7) Alternative Conceptions Revealed (AC): AC1 -Proof is more valid than disproof. (4) AC2 -Both words are equally valid (respondents indicate"' no need for falsifiability in science). (1) AC3 -It's easier to deny/disprove something than to prove it (respondents indicate no need for falsifiability in science). (8) No Response Recorded: (12) No Response Recorded: (11) 164 165 S C Scientists try to disprove AC1 Proof is more valid than AC2 Both words are equally AC3 It's easier to their hypotheses, they do not disproof. valid. deny/disprove something look for proof. than to prove it. Figure 18. Comparison of detailed pre unit and post unit conceptions 166 Item 14: The fossil record shows that the ancestors of giraffes did not have long necks. Formulate an explanation for how you think giraffes got their long necks. Scientific Conception: Adaptive evolution is the result of natural selection acting on heritable variation. Variation in neck lengths exists in the ancestral giraffe population. Environmental factors favored the long neck variation over the short neck variation. The long neck variation enjoyed higher reproductive success, and left more offspring with the trait for long necks in subsequent generations. Table C14 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=18) Post Unit Conceptions (n=26) Post Unit Conceptions That Compare With Pre Unit Conceptions New Post Unit Alternative Conceptions Scientific Conceptions Revealed (SC): SC -Darwinian (neo Darwinian) evolution. Genetic/phenotypic variation plus selection. (5) Scientific Conceptions Revealed (SC): SC -Darwinian (neo Darwinian) evolution. Genetic/phenotypic variation plus selection. (21) Alternative Conceptions Revealed (AC): A C 1 -Strong Lamarckian evolution. Organisms change based on stretching, or deciding to grow long necks. (3) AC2 -Weak Lamarckian evolution. Organisms change because they need to change. (6) AC3 -Mating/interbreeding scenarios for evolution. Short-necked giraffes mated with some long-necked animal, resulting in offspring with longer necks. (4) Alternative Conceptions Revealed (AC): AC1 -Strong Lamarckian evolution. Organisms change based on stretching, or deciding to grow long necks. (1) AC2 -Weak Lamarckian evolution. Organisms change because they need to change. (1) AC3 -Mating/interbreeding scenarios for evolution. Short-necked giraffes mated with some long-necked animal, resulting in offspring with longer necks. (0) New Alternative Conception Revealed (NAC): - A mixture of Darwinian and Lamarckian mechanisms (survival plus need). (3) No Response Recorded: (10) No Response Recorded: (2) 167 72% I Pre Unit Totals I Post Unit Totals AC Adaptive evolution in the giraffe neck length is Lamarckian (or some non Darwinian mechanism). 168 Figure 19. Comparison of pre unit and post unit conceptions 100% 90% — 80% 70% 60% 50% 40% 30% 20% - B 10% 0% 91% 2 8 % ~rr%-4% 33% 4% 22% • Pre Unit Totals • Post Unit Totals 0% SC Adaptive evolution in the AC1 Adaptive evolution in the AC2 Adaptive evolution in the AC3 Adaptive evolution in the giraffe neck length is giraffe neck length is strong giraffe neck length is weak giraffe neck length is based Darwinian (natural selection Lamarckian based on Lamarckian based on need, on mating/interbreeding with acting on heritable variation). stretching. long necked organisms. 169 Figure 20. Comparison of detailed pre unit and post unit conceptions 170 Comparison of Pre and Post Unit Conceptions for Bishop and Anderson Survey Item 1: Cheetahs (large African cats) are able to run faster than 60 miles per hour when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could only run 20 miles per hour? Scientific Conception: Adaptive evolution in cheetah speed is Darwinian (natural selection acting on heritable variation). Table CI5 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=17) Post Unit Conceptions (n=25) Post Unit Conceptions That Compare With Pre Unit Conceptions New Post Unit Alternative Conceptions Scientific Conceptions Revealed (SC): SC -Darwinian (neo Darwinian) evolution. Genetic/phenotypic variation plus environmental selection. (5) Scientific Conceptions Revealed (SC): SC -Darwinian (neo Darwinian) evolution. Genetic/phenotypic variation plus environmental selection. (16) Alternative Conceptions Revealed (AC): AC1 -Lamarckian evolution. Use and disuse, and inheritance of acquired characteristics. The cheetahs decided to, or tried to, get faster. (10) AC2 - Mating/interbreeding scenarios for evolution. The slow cheetahs mated with fast animals, resulting in fast cheetahs. (1) AC3 -Biologists are just assuming (there is some doubt about whether or not evolution even occurred). (1) Alternative Conceptions Revealed (AC): AC1 -Lamarckian evolution. Use and disuse, and inheritance of acquired characteristics. The cheetahs decided to, or tried to, get faster. (6) AC2 - Mating/interbreeding scenarios for evolution. The slow cheetahs mated with fast animals, resulting in fast cheetahs. (0) AC3 -Biologists are just assuming (there is some doubt about whether or not evolution even occurred). (0) New Alternative Conception Reveled (NAC): -Mixture of Darwinian and Lamarckian mechanisms. Cheetahs needed to get faster so the successful ones passed their genes on to the next generation. (3) No Mechanism presented, therefore no conception regarding mechanism assigned: No Mechanism presented, therefore no conception regarding mechanism assigned: 171 (10) No Response Recorded: (1) (3) 172 • Pre Unit Totals • Post Unit Totals SC Adaptive evolution in cheetah speed is Darwinian AC Adaptive evolution in cheetah speed is Lamarckian (or (natural selection acting on heritable variation). some non Darwinian mechanism). Figure 21. Comparison of pre unit and post unit conceptions 173 80% 70% 60% 4 50% 40% 30% 20% 10% 0% 73% 29% 59% S Pre Unit Totals • Post Unit Totals SC Adaptive evolution in AC1 Adaptive evolution in AC2 Adaptive evolution is due AC3 Biologists are just cheetah speed is Darwinian cheetah speed is to mating/interbreeding with assuming (some doubt about (natural selection acting on Lamarckian. fast organisms. whether or not evolution heritable variation). occurred). Figure 22. Comparison of detailed pre unit and post unit conceptions 174 Item 2: Cave salamanders are blind (they have eyes which are nonfunctional). How would a biologist explain how blind cave salamanders evolved from sighted ancestors? Scientific Conception: Loss of sight in cave salamanders is Darwinian (absence of natural selection acting = accumulated mutations). Table C16 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=21) Post Unit Conceptions (n=22) Post Unit Conceptions That Compare With Pre Unit Conceptions New Post Unit Alternative Conceptions Scientific Conceptions Revealed (SC): SCI-Darwinian evolution. Sight not necessary for survival. Deleterious mutations in a functional organ that no longer effects survival, are not selected against. (3) SC2 - Mendelian genetics. Genes affect traits; blindness caused by a mutated gene or a blind gene that increased in frequency. (7) Scientific Conceptions Revealed (SC): SCI-Darwinian evolution. Sight not necessary for survival. Deleterious mutations in a functional organ that no longer effects survival, are not selected against. (5) SC2 -Mendelian genetics. Genes affect traits; blindness caused by a mutated gene or a blind gene that increased in frequency. (4) Alternative Conceptions Revealed (AC): AC1 -Lamarckian evolution. Use and disuse, and inheritance of acquired characteristics, plus Salamanders developed other senses to compensate for loss of sight. (5) AC2 -Lamarckian evolution. Use and Alternative Conceptions Revealed (AC): AC1 -Lamarckian evolution. Use and disuse, and inheritance of acquired characteristics, plus Salamanders developed other senses to compensate for loss of sight. (0) AC2 -Lamarckian Evolution. Use and New Alternative Conception Revealed (NAC): -Vestigial structures arise though the Lamarckian mechanism of use and disuse. (7) 175 disuse, and inheritance of acquired characteristics. (5) AC3 - A mass epidemic caused blindness in the salamander population. (1) disuse, and inheritance of acquired characteristics. Sight not needed/used, therefore they lost their sight through lack of use (disuse). (6) AC3 -A mass epidemic caused blindness in the salamander population. (0) No Mechanism Presented therefore no conception regarding mechanism assigned: (5) No Response Recorded: (2) No Mechanism Presented therefore no conception regarding mechanism assigned: (4) No Response Recorded: (2) 176 • Pre Unit Totals • Post Unit Totals 30% 4 S C Loss of sight in cave salamanders is Darwinian (absence A C Loss of sight in cave salamanders is Lamarckian (or of natural selection acting = accumulated mutations). some non Darwinian mechanism). Figure 23. Comparison of pre unit and post unit conceptions 45°/c 40% 35% 30% 25% 20% 15% 4-10% SC1 Darwinian SC2 Mendelian evolution, sight not genetics, blindness necessary for survival, caused by a mutated deleterious mutations gene, or a blind gene not selected against. that increased in frequency. 249 0% 40% AC1 Lamarckian evolution, plus salamanders developed other senses to compensate. AC2 Lamarckian evolution. Figure 24. Comparison of detailed pre unit and post unit conceptions 5% o% HPre Unit Totals • Post Unit Totals AC3 A mass epidemic caused blindness. 178 Item 3: Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists explain that ducks evolved from land birds which did not have webbed feet. Item 3 a: The trait of webbed feet in ducks: Appeared in ancestral 12345 Appeared in ducks ducks because they lived because of a chance in water and needed mutation. webbed feet to swim. Scientific Conception: Webbed feet appeared in ducks because of a chance mutation. Table CI7 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28) Scientific Conceptions Revealed (SC): (0) SC -Neo Darwinian explanation. Mutation is the reason for the appearance of a novel trait. Webbed feet appeared because of a chance mutation. Scientific Conceptions Revealed (SC): (6) SC -Neo Darwinian explanation. Mutation is the reason for the appearance of a novel trait. Webbed feet appeared because of a chance mutation. Alternative Conceptions Revealed (AC): AC1 -Lamarckian explanation. Need is the driving force behind the appearance of a novel trait. Mutation does not cause appearance of a novel trait. (8). AC2 -Chiefly Lamarckian explanation. Novel traits appear chiefly because of need, but mutation plays a small but necessary role as well. (10). AC3 -Novel traits appear due to a combination of both neo Darwinian (mutation) and Lamarckian (need) explanations. (8). AC4 -Novel traits appear chiefly because of mutation, but need plays a small but necessary role as well. (2) Alternative Conceptions Revealed (AC): AC1 -Lamarckian explanation. Need is the driving force behind the appearance of a novel trait. Mutation does not cause appearance of a novel trait. (4). AC2 -Chiefly Lamarckian explanation. Novel traits appear chiefly because of need, but mutation plays a small but necessary role as well. (2). AC3 - Novel traits appear due to a combination of both neo Darwinian (mutation) and Lamarckian (need) explanations. (13). AC4 -Novel traits appear chiefly because of mutation, but need plays a small but necessary role as well. (3) 179 • Pre Unit Totals • Post Unit Totals SC Webbed feet appeared because of a chance mutation. AC Webbed feet appeared because ducks needed webbed feet. Figure 25. Comparison of pre unit and post unit conceptions 180 • Pre Unit Totals • Post Unit Totals SC NeoDarwinian AC 1 Lamarckian AC2 Lamarckian Novel AC3 Novel traits AC4 Novel traits explanation. Mutation explanation. Need is traits appear chiefly appear due to a appear chiefly because is the reason for the the driving force behind because of need, but combination of both of mutation, but need appearance of a novel the appearance of mutations play a role as need and mutation. plays a role as well. trait (webbed feet). novel trait. well. Figure 26. Comparison of detailed pre unit and post unit conceptions 181 Item 3 b: While ducks were evolving webbed feet With each generation, most ducks had about the same amount of webbing on their feet as their parents. With each generation most ducks had a tiny bit more webbing on their feet than their parents. Scientific Conception: With each generation most ducks had about the same amount of webbing on their feet as parents. Table CI8 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=27) Scientific Conceptions Revealed (SC): SCI -Most ducks possess about the same amount of webbing on their feet as their parents. (2). SC2 -Most ducks possess about the same amount of webbing on their feet as their parents, but there were also a high number of ducks that had slightly more webbing on their feet than their parents. (2) SC3 -The number of ducks that had the same amount of webbing as their parents was equal to the number of ducks that had more webbing on their feet than their parents. (5) Scientific Conceptions Revealed (SC): SCI -Most ducks possess about the same amount of webbing on their feet as their parents. (1). SC2 -Most ducks possess about the same amount of webbing on their feet as their parents, but there were also a high number of ducks that had slightly more webbing on their feet than their parents. (3) SC3 -The number of ducks that had the same amount of webbing as their parents was equal to the number of ducks that had more webbing on their feet than their parents. (6) Alternative Conceptions Revealed (AC): AC1 -Most ducks had a tiny bit more webbing on their feet than their parents, but there were also a high number of ducks that had the same amount of webbing as their parents. (14) AC2 -Most ducks had a tiny bit more webbing on their feet than their parents. (5) Alternative Conceptions Revealed (AC): A C 1 -Most ducks had a tiny bit more webbing on their feet than their parents, but there were also a high number of ducks that had the same amount of webbing as their parents. (6) AC2 -Most ducks had a tiny bit more webbing on their feet than their parents. (11) 182 No Response Recorded: (1) 183 80% 70% 1 60% 50% 40% 30% 20% 10% Pre Unit Totals Post Unit Totals SC With each generation most ducks had about the same AC With each generation most ducks had a tiny bit more amount of webbing as parents. webbing than parents. Figure 21. C o m p a r i s o n o f pre unit and post unit conceptions 184 FJ Pre Unit Totals • Post Unit Totals SC1 Most ducks SC2 Most ducks SC3 The number of AC1 Most ducks AC2 Most ducks had a possess about the possess the same ducks with the same possess more webbing, tiny bit more webbing same amount of amount of webbing, but webbing was equal to but also a high number on their feet than their webbing as their also a high number the number of ducks possessed the same. parents, parents. possess slightly more. with more webbing. Figure 28. Comparison of detailed pre unit and post unit conceptions 185 Item 3 c: If a population of ducks were forced to live in an environment where water for swimming was not available Many ducks would die 1 2345 The ducks would because their feet were gradually develop poorly adapted to this nonwebbed feet. environment. Scientific Conception: Many ducks would die because their feet were poorly adapted to this environment. Table C19 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28) Scientific Conceptions Revealed (SC): SCI -Many ducks would die. (4) SC2 -Many ducks would die, but some evolution towards non-webbed feet would occur too. (1) SC3 -The environmental pressure causing death of the individual is equally as effective at causing evolution of the population. (8) Scientific Conceptions Revealed (SC): SCI -Many ducks would die. (4) SC2 -Many ducks would die, but some evolution towards non-webbed feet would occur too. (2) SC3 -The environmental pressure causing death of the individual is equally as effective at causing evolution of the population. (8) Alternative Conceptions Revealed (AC): A C 1 -The environment would have a greater effect at causing the population to evolve rather than causing individual ducks to die. (9) AC2 -The ducks would gradually evolve. (6) Alternative Conceptions Revealed (AC): AC1 -The environment would have a greater effect at causing the population to evolve rather than causing individual ducks to die. (7) AC2 -The ducks would gradually evolve. (7) 186 • Pre Unit Totals • Post Unit Totals S C Many ducks would die. A C The ducks would gradually develop webbed feet. Figure 29. Comparison of pre unit and post unit conceptions 187 35% 30% 25% 20% i 15% 10% \ IPre Unit Totals Post Unit Totals 0% H SC1 Many ducks would SC2 Many ducks would SC3 Environmental AC 1 Environmental AC2 The ducks would die. die, but some evolution pressure causing death pressure would have a gradually evolve, towards non-webbed is equally as effective at greater effect at feet would occur. causing evolution. causing population evolution rather than individual death. Figure 30. Comparison of detailed pre unit and post unit conceptions 188 Item 3 d: The population of ducks evolved webbed feet because: The more successful ducks 12345 The less successful ducks adapted to their aquatic died without offspring. environment. Scientific Conception: The less successful ducks died without offspring. Table C20 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28) Scientific Conceptions Revealed (SC): SCI -The effect, on evolution, of successful ducks surviving, and unsuccessful ducks dying, would be the same. (8) SC2 -The less successful ducks dying without offspring would have a greater effect on evolution of webbed feet than the more successful ducks adapting to their environment. (4). SC3 -The less successful ducks dying without leaving offspring is the driving force behind the evolution of webbed feet. (0) Scientific Conceptions Revealed (SC): SCI -The effect, on evolution, of successful ducks surviving, and unsuccessful ducks dying, would be the same. (14) SC2 -The less successful ducks dying without offspring would have a greater effect on evolution of webbed feet than the more successful ducks adapting to their environment. (2). SC3 -The less successful ducks dying without leaving offspring is the driving force behind the evolution of webbed feet. (2) Alternative Conceptions Revealed (AC): A C 1 -The more successful ducks adapting to their environment is the driving force behind the evolution of webbed feet. (7) AC2 -The successful ducks adapting to their environment would have a greater effect on evolution of webbed feet than the less successful ducks dying without offspring. (9) Alternative Conceptions Revealed (AC): AC1 -The more successful ducks adapting to their environment is the driving force behind the evolution of webbed feet. (7) AC2 -The successful ducks adapting to their environment would have a greater effect on evolution of webbed feet than the less successful ducks dying without offspring. (3) 189 SC The less successful ducks died without offspring. Figure 31. Comparison of pre unit and post unit conceptions 57% HPre Unit Totals • Post Unit Totals AC The more successful ducks adapted. 60% TW 50% 40% j 20% \ 10% 0% \ 50% 32% 30% + 29%. HPre Unit Totals • Post Unit Totals SC1 The effect of successful ducks surviving and unsuccessful ducks dying would be the same. SC2 The less SC3 The less successful ducks dying successful ducks dying would have a greater is the driving force effect than the more behind the evolution of successful ducks webbed feet, adapting. Figure 32. Comparison of detailed pre unit and post unit conceptions AC1 The more AC2 The more successful ducks successful ducks adapting is the driving adapting would have a force behind the greater effect than the evolution of webbed less successful ducks feet. dying. 191 Item 4: A number of mosquito populations are today resistant to DDT, even though those species were not resistant to DDT when it was first introduced. Biologists would explain that DDT resistance evolved in mosquitos because: (choose the best answer) a. Individual mosquitos built up an immunity to DDT after being exposed to it. b. Mosquitos needed to be resistant to DDT in order to survive. c. A few mosquitos were probably resistant to DDT before it was ever used. d. Mosquitos learned to adapt to their environment. e. Other; please explain Scientific Conception: c. A few mosquitos were probably resistant to DDT before it was ever used. Table C21 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=26) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28) Scientific Conceptions Revealed (SC): SC -c -Mutation for resistance was in population before DDT exposure (Neo Darwinian). (3) Scientific Conceptions Revealed (SC): SC -c -Mutation for resistance was in population before DDT exposure (Neo Darwinian). (9) Alternative Conceptions Revealed (AC): AC1 -a - Mosquitos became immune to DDT after exposure. The organism responds to the environment with some kind of internal will to change (Lamarckian). (12) AC2 -b -Need. Organisms change because they need to change, and set about acquiring the characteristics that they need (Lamarckian). (4) AC3 -d -Learn to adapt to environment. Organisms respond to the environment with some kind of internal will to change Alternative Conceptions Revealed (AC): AC1 -a - Mosquitos became immune to DDT after exposure. The organism responds to the environment with some kind of internal will to change (Lamarckian). (11) AC2 -b -Need. Organisms change because they need to change, and set about acquiring the characteristics that they need (Lamarckian). (4) AC3 -d -Learn to adapt to environment. Organisms respond to the environment with some kind of internal will to change 192 (Lamarckian). (6) AC4 -e -Other; all of the above. (1) (Lamarckian). (3) AC4 -e -Other; all of the above. (1) No Response Recorded: (2) 193 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 32% 12% 88% 68% SC NeoDarwinian explanation. Mutation for resistance was AC Lamarckian explanation, or some other non-in the population before DDT exposure. NeoDarwinian explanation. Figure 33. Comparison of pre unit and post unit conceptions I Pre Unit Totals I Post Unit Totals 194 50% n 45% 40% 35°/ 30% 25% H •— 20% 15% 10% BPre Unit Totals • Post Unit Totals SC Mutation for AC1 Individual AC2 Mosquitos needed AC3 Mosquitos learned AC4 Other, resistance was in the mosquitos built up an to be resistant. to adapt to their population before DDT immunity to DDT after environment, exposure. being exposed. Figure 34. Comparison of detailed pre unit and post unit conceptions 195 Item 5: Biologists often use the term "fitness" when speaking of evolution. Below are descriptions of four male lions. According to your understanding of evolution, which lion would biologists consic er the "fittest"? Name George Ben Spot Sandy Size 10 feet/1751bs 8 feet/160 lbs 9 feet/162 lbs 9feet/160 lbs Number of cubs fathered 19 25 20 20 Age of death 13 years 16 years 12 years 9 years Number of cubs surviving to adulthood 15 14 14 19 Comments George is very large, very healthy. The strongest lion. Ben has the greatest number of females in his harem. When the area that Spot lived in was destroyed by fire, Spot was able to move his pride to a new area & change his feeding habits. Sandy was killed by an infection resulting from a cut on his foot. The "fittest" lion is: a. George b. Ben c. Spot d. Sandy Scientific Conception: -d. Sandy is the fittest. Fitness means having the most offspring reach reproductive maturity. 196 Table C22 Comparison of Pre and Post Unit Conceptions Pre Unit Conceptions (n=28) Post Unit Conceptions That Compare With Pre Unit Conceptions (n=28) Scientific Conceptions Revealed (SC): SC -d. Sandy -Fittest = Having the most offspring reach reproductive maturity. (7) Scientific Conceptions Revealed (SC): SC -d. Sandy -Fittest = Having the most offspring reach reproductive maturity. (8) Alternative Conceptions Revealed (AC): AC1 -a. George -Fittest = Strongest. (5) AC2 -b. Ben -Fittest = Live the longest. (3) AC3 -c. Spot -Fittest = The ability of an individual to adapt within one's lifetime to changes that occur in the environment. (13) Alternative Conceptions Revealed (AC): A C 1 -a. George -Fittest = Strongest. (0) AC2 -b. Ben -Fittest = Live the longest. (4) AC3 -c. Spot -Fittest = The ability of an individual to adapt within one's lifetime to changes that occur in the environment. (16) 197 80% i 70% 60% 50% H 40% 30% 20% 10% 0% 25% 75% 71 c • Pre Unit Totals • Post Unit Totals SC Sandy. -Fitness = Having the most offspring reach reproductive maturity. AC George, Ben, Spot. -Fitness = something other than having the most offspring reach reproductive maturity. Figure 3 5 . Comparison of pre unit and post unit conceptions 198 60% 50% 40% H 30% 20% 10% i 0% 25% Tg%~ 0% SC Sandy AC1 George 14% AC2 Ben Figure 36. Comparison of detailed pre unit and post unit conceptions 4 6 % I Pre Unit Totals I Post Unit Totals AC3 Spot 

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