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Preliminary Evolutionary Explanations: A Basic

Framework for Conceptual Change and Explanatory

Coherence in Evolution

Kostas Kampourakis Vasso Zogza

Springer Science+Business Media B.V. 2008

Abstract This study aimed to explore secondary students explanations of evolutionary

processes, and to determine how consistent these were, after a specific evolution instruc-

tion. In a previous study it was found that before instruction students provided different

explanations for similar processes to tasks with different content. Hence, it seemed that the

structure and the content of the task may have had an effect on students explanations. The

tasks given to students demanded evolutionary explanations, in particular explanations for

the origin of homologies and adaptations. Based on the conclusions from the previousstudy, we developed a teaching sequence in order to overcome students preconceptions, as

well as to achieve conceptual change and explanatory coherence. Students were taught

about fundamental biological concepts and the several levels of biological organization, as

well as about the mechanisms of heredity and of the origin of genetic variation. Then, all

these concepts were used to teach about evolution, by relating micro-concepts (e.g.

genotypes) to macro-concepts (e.g. phenotypes). Moreover, during instruction students

were brought to a conceptual conflict situation, where their intuitive explanations were

challenged as emphasis was put on two concepts entirely opposed to their preconceptions:

chance and unpredictability. From the explanations that students provided in the post-test it

is concluded that conceptual change and explanatory coherence in evolution can be

achieved to a certain degree by lower secondary school students through the suggested

teaching sequence and the explanatory framework, which may form a basis for teaching

further about evolution.

K. Kampourakis (&)Geitonas School, P.O. Box 74128, Vari Attikis, 16602 Athens, Greece

e-mail: [email protected]

V. Zogza

Department of Sciences of Education and Early Childhood Education, University of Patras, 26500

Rion, Patras, Greece

e-mail: [email protected]

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Sci & Educ

DOI 10.1007/s11191-008-9171-5


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1 Introduction

Evolution is a central, unifying theme in biology because it can explain both the unity and the

diversity of life. However, as a teaching subject it is a rather difficult one because its

understanding is based on concepts stemming from a variety of disciplines and because itsacceptance may be influenced by personal worldviews. In particular, to understand evolution

one needs to be able to handle concepts such as those used in paleontology, embryology,

biogeography, molecular biology, and population genetics (Mayr 2002, pp. 1239). More-

over, it seems that acceptance of evolution is often difficultly achieved because of the

religious and political issues involved (Miller et al. 2006), and because it appears to be

counter-intuitive (Bloom and Weisberg 2007). Over the years evolution education has been a

particularly active research field focusing on students preconceptions about evolution,

students and teachers understanding and acceptance of evolution, as well as on several

approaches for teaching and learning. However, in many cases evolution instruction in both

secondary and tertiary settings has been found to provide moderate and temporary cognitive

outcomes. Secondary school students but mostly college students and undergraduates have

been found unprepared to understand what evolution is all about and to usually gain a partial

understanding of related themes (for overviews see Alters 2005; McComas et al. 2006).

Teaching evolution can be a considerably challenging task for teachers due to particular

conceptual difficulties that influence learning. In general, to teach effectively about science

teachers primarily need to identify their students preconceptions, as these may form

obstacles in both understanding and accepting the scientific concepts taught (Carey 2000).

As soon as these preconceptions have been documented, they ought to be taken into

account in designing an instruction that will aim at promoting conceptual change. How-ever, evolutionary processes, like natural selection, are complex processes that demand a

thorough understanding of several concepts; some of them fall directly within the disci-

pline of evolutionary biology (e.g. the existence of genetic variation within a population),

whereas others do not but can be fundamental to learning evolutionary concepts (e.g. the

mechanisms by which genetic variation within a population is produced). Consequently,

the process of conceptual change in evolution is not a simple, straightforward process

concerning one particular concept but one that demands that students have built an

understanding of a complex network of inter-related concepts. In addition, conceptual

change in evolution is not just replacing old concepts (e.g. need driven adaptation of

individuals) with new ones (e.g. adaptation of populations through natural selection). Wesuggest that conceptual change in evolution should rather be a process of replacing an old

explanatory framework with a new, more efficient and more scientifically acceptable one.

Moreover, concluding that students may accommodate a new explanatory framework can

be necessary but not sufficient for a successful evolution instruction. It has been found that

students may exhibit both alternative and scientifically acceptable conceptions and bring

different ones into play in response to different problem contexts (Palmer 1999). Conse-

quently, it is important that students explanations to different problem contexts after

instruction are compared to each other, and not only to the ones provided before instruction.

Instruction of a new explanatory framework cannot be successful if students are not foundable of applying it coherently to different problem contexts. If students explanations to

different tasks do not cohere, it can only be concluded that they have gained a partial

understanding of the concepts they were taught. We suggest that any evolution instruction can

be effective only if students are finally found to exhibit explanatory coherence.

In a previous study of students intuitive explanations of evolution, in particular of the

causes of homologies and adaptations, it was found that in most cases teleological

K. Kampourakis, V. Zogza

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explanations predominated. In general students explanations can be classified as teleo-

logical, proximate or evolutionary. For example, in order to explain the coloration of the

body that provided concealment to its possessors in a particular environment, students gave

different types of explanations: (a) evolutionary explanations that referred to past processes

in populations (I think that these animals used to have other colors in earlier times but astime went by only those who had the same color with their environment managed to survive

because they could hide better from the animals that threatened them. On the contrary, the

animals with other colors were more easily identified. Thus, only those animals that had

the same color with their environment survived), (b) proximate explanations that were

based on current properties of individuals (These animals were influenced by their

environment and the respective climate and thus they acquired these features), and (c)

and teleological explanations that were based on purposes or predetermined plans or goals

(In order to overcome same dangerse.g. being identified by other animals or man-they

were obliged to acquire some features, to imitate features of other organisms so that it

could be hard for their enemies to identify them). Students explanations of the origin of

homologies provided evidence that the unconscious bias of thinking anthropomorphically

may drive them to attribute the similarities of organisms but not of cells to a kind of

kinship among them. Hence, it was concluded that the level of reference (species or cells)

had an influence on students explanations. On the other hand, from students explanations

of the origin of adaptations it was concluded that the less was the information relative to a

task provided to students, the larger was the number of teleological explanations whereas

the more was the information provided to students, the larger was the number of evolu-

tionary explanations. Hence, in general it was concluded that the content of the task had an

influence on students explanations and that students did not exhibit explanatory coherence(Kampourakis and Zogza 2008).

The aim of this study is to explore the effectiveness of a specially designed teaching

sequence, taking into account students preconceptions, in (a) promoting conceptual

change from 14 to 15 years old students intuitive explanations to a particular type of

scientific explanations, preliminary evolutionary explanations, and (b) achieving explan-

atory coherence after instruction.

2 Theoretical Background

2.1 Teaching, Learning, Understanding and Accepting Evolution

A plurality of instructional strategies has been applied over the years to teach about

evolution. While most of the studies focused on the analysis of students preconceptions

and on conceptual change, their results and conclusions vary in several aspects. However,

they all agree that most evolution instructions usually yield moderate results in students

understanding of the subject. These studies have been performed in secondary and post-

secondary settings. In what follows, studies with secondary school students are presented

separately from studies with college students or undergraduates and the focus is on factorsthat influence understanding of evolution. Then the relation between understanding and

acceptance of evolution is discussed.

Studies with secondary school students have shown that only a moderate understanding

of evolution can be achieved after instruction. There are several reasons for this. Although

students may possess adequate factual knowledge, they often have difficulties in using that

for constructing explanations because it is difficult for them to realize what they are really

Preliminary Evolutionary Explanations

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asked to explain, probably due to the persistence of their preconceptions. In addition,

students often exhibit inconsistencies in their answers, when they use different ideas for the

same problem presented in different contexts. When there is a replacement of their initial

explanations with new ones presented to them during instruction, it neither includes the

majority of the students, nor reflects a reorganization of their concepts. And as manyconceptions in the content area of evolution are closely interrelated, a change in one

conception requires a change in many others (Hallden 1988; Jimenez-Aleixandre 1992;

Settlage 1994; Demastes et al. 1996). The influence of preconceptions on understanding

evolution is more apparent when they are related to their religious beliefs, and the stronger

students religious commitments were, the more negatively they contributed to an initial

belief in evolution and to a shift towards evolution during instruction (Lawson and

Worsnop 1992). We should note however that special creation and evolution should not be

presented as alternative hypotheses, because this might confuse the understanding of the

nature of science (Smith et al. 1995). It seems that evolution instruction can be more

successful when students are not only taught how to provide explanations, but also when

they are given the chance to discuss them in classroom and compare them to their previous

ideas. And when they are taught about the conceptual structure of models (e.g. from the

history of science) and use them to explain phenomena, they can develop a better

understanding. Finally, the study of inheritance in close relation to the study of evolution

may help them understand the origin of variation which in turn might provide a better

understanding of the mechanisms of evolution (Jimenez-Aleixandre 1992; Demastes et al.

1995; Passmore and Stewart 2002; Banet and Ayuso 2003).

As far as understanding is concerned, the results of studies with college students and

undergraduates have been quite similar to those with secondary school students. But inmany cases the relation between understanding and acceptance of evolution has been more

thoroughly examined at this level. At first, no relationship seems to exist between the

number of previous biology courses and pre-test performance. On the other hand, belief in

the truthfulness of evolutionary theory can be unrelated to post-test performance, as stu-

dents who improve their understanding of evolution during the course may not generally

change their beliefs about the truthfulness of evolutionary theory (Bishop and Anderson

1990; Demastes et al. 1995). The historical presentation of the development of evolu-

tionary theory can promote a better understanding of its content, but while students may

generally increase their use of Darwinian ideas it seems more difficult to reduce their use of

non-Darwinian ideas (Jensen and Finley 1996). To face such problems a diagnostic test fornatural selection was developed that did not address students understanding of the process

of natural selection itself but rather their understanding of the underlying concepts of

genetics and ecology that serve as the basis for the application of natural selection as an

explanatory mechanism (Anderson et al. 2002).

Besides understanding, the relation between understanding and acceptance of evolution

has been extensively studied at the post-secondary level. Students may misunderstand the

nature of evolutionary theory due to factors shaped by their beliefs. Teaching about the

nature of science is more likely to enhance understanding of evolutionary theory if students

are given the opportunity to discuss their beliefs in relation to scientific knowledge (Dagherand BouJaoude 1997, 2005). Students may also perceive a negative impact of evolutionary

theory on the social and the personal aspects of life as they regard the consequences of

accepting evolution more negative, the more time it was given to its teaching (Brem et al.

2003). But this may not always be the case. Interestingly enough, no relationship may exist

between the understanding and the acceptance of evolution. Students may have an

understanding of evolutionary theory without accepting its validity, or alternatively, they


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may accept the validity of the theory based upon a poor understanding of it. When ideas are

related to firmly-held beliefs, as is the case for biological evolution, the disposition toward

changing ones views may play a more significant role in determining acceptance than

background knowledge, whereas students initial acceptance of evolution does not have to

influence their subsequent learning of the subject (Sinatra et al. 2003; Ingram and Nelson2006). In the cases that students have a meaningful understanding of evolution but still

disbelieve, the appropriate goal for science education may be that students realize that the

theory in question affords the best current scientific account of the relevant phenomena

based on the available empirical evidence (Smith and Siegel 2004).

Considering all the above, it is not clear to what extent personal worldviews may

influence understanding of evolution as contradictory findings exist among the several

research groups. Hence, in this study this very important aspect was not investigated and

we focused instead solely on issues related to understanding evolution. Given the fact that

most studies have involved secondary school or older students, we considered more

interesting to investigate students understanding of evolution at the lower secondary

school level. This was also based on our assumption that the sooner students precon-

ceptions about evolution are challenged, the easier it will be to help them reject their

preconceptions and accommodate scientific ones. And, since the involvement of students in

constructing explanations (Jimenez-Aleixandre 1992) and the emphasis put on genetics

during instruction (Banet and Ayuso 2003) seem to have been factors that have promoted a

better understanding of evolution in secondary school we considered interesting to

investigate their effect further at the lower secondary school level.

2.2 Conceptual Change in Evolution

In several studies it has been documented that students in general tend to attribute the origin of

the traits that several organisms possess to a predetermined plan or to the achievement of a

purpose or a desired goal. In many of these studies students preconceptions about evolution

have been characterized as Lamarckian. However, it has been shown that this characterization

does not adequately describe secondary students preconceptions (Kampourakis and Zogza

2007). One way to study students preconceptions is to analyze the explanations they provide

to open ended tasks. This is expected to give students the opportunity to express their views in

more detail. Students at the lower secondary school level (1415 years old) have been found

to provide predominantly teleological explanations for the origin of biological traits(Kampourakis and Zogza 2008). Hence, what could be a major aim of any evolution

instruction at this level would be to promote conceptual change: a shift from students

intuitive explanations to evolutionary explanations.

There are two possible outcomes in the process of conceptual change. The first is

assimilation of new concepts when students use existing concepts to deal with new phe-

nomena and preserve some of their initial preconceptions. The second is accommodation

when students find their current concepts inadequate for grasping the new phenomenon

successfully and replace or reorganize their central concepts. It is obvious that accommo-

dation is the most desired outcome of a conceptual change process so that students will

abandon their initial concepts and accommodate new ones. To achieve this, certain conditions

need to be fulfilled: (a) there must be a dissatisfaction with existing concepts, (b) new

concepts must be intelligible, (c) new concepts must be initially appear plausible, and (d) new

concepts have to suggest the possibility of a fruitful research program (Posner et al. 1982).

But conceptual change may be more than just replacing old concepts with new ones; it might

be replacing an old explanatory framework (defined here as a pattern of constructing


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explanations) with a new one. Hence, conceptual change from intuitive to evolutionary

explanations can be achieved as long as the following conditions are fulfilled: (a) there must

be a dissatisfaction with existing explanations; students must have found the explanations

they use insufficient to explain, (b) new explanations must be intelligible; students must have

found new explanations easy to understand and to apply to new cases, (c) new explanationsmust initially appear plausible; students must have found new explanations sufficient to

explain phenomena they have been previously unable to explain, and (d) new explanations

should suggest the possibility of a fruitful research program; new explanations should be

applicable to many new cases and should have the potential to open new areas of inquiry.

Based on all the above, we suggest that a conceptual change process from intuitive to

evolutionary should include the following stages:

(a) Documentation of students preconceptions through the analysis of the explanations

they provide to particular tasks. Having students construct explanations would

provide the opportunity of identifying not only their preconceptions but also the waythey relate several concepts to each other and use them to construct explanations.

(b) Bring students to a conceptual conflict situation, where their explanations would be

challenged. Having students construct particular explanations that are in contrast with

their intuitive explanations might lead them to question the latter and perhaps

accommodate the new explanatory framework.

(c) Instruct students how to apply the new explanatory framework to novel cases and put

emphasis on its advantages. If students finally consider the new explanations more

efficient from the initial ones they used, they might eventually reject the latter and

accommodate the former. Conceptual change from their intuitive explanations to new

ones will have thus occurred.

Perhaps the more critical of these stages is the stage of conceptual conflict. Three con-

ditions need to be fulfilled in order that students experience conceptual conflict between

two conceptions: (a) both conceptions have to be intelligible, (b) both conceptions have to

be comparable, and (c) only one of the two conceptions has to be plausible (Hewson and

Hewson 1984). Hence, for conceptual conflict to occur between explanations it is necessary

that: (a) both explanations have to be intelligible; if students cannot understand both of

them, there can be no conflict, (b) both explanations have to be comparable; students will

be able to realize that the two explanations are in conflict only if they have some basis for

comparison, and (c) only one of the two explanations has to be plausible; students have toapply both explanations to new cases and realize that only one of them is plausible.

Given the fact that students intuitive explanations of evolution are predominantly

teleological, a concept that would bring students to a conceptual conflict situation might be

contingency, defined as the affirmation of control by immediate events over destiny

(Gould 2000/1989, p. 284). This idea was illustrated by the metaphor of the tape: You

press the rewind button and, making sure you thoroughly erase everything that actually

happened, go back to any time and place in the past Then let the tape run again and see if

the repetition looks at all like the original (p. 48), any replay of the tape would lead

evolution down a pathway radically different from the road actually taken (p. 51). The

evolutionary contingency thesis suggests that the history of life on earth has been deter-

mined by contingent events. For example, mutations and natural selection in changing

environments are two sources of contingency (Beatty 1995). There are two versions of

contingency: the unpredictability version and the causal dependence version (Beatty 2006).

Both of them are important for instruction. It is important for students to understand that

there several possible evolutionary pathways (contingencies); that it is impossible to


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predict in advance which of them is going to actually be taken (unpredictability) and that

there are certain constraints in the possible outcomes once a specific pathway is taken

(causal dependence). It should be noted here that the importance of contingency for

evolution has been criticized on the basis of evidence for convergent evolution, the process

of acquiring similar traits independently and not of inheriting them from a commonancestor (Conway Morris 2003). However, it has been argued that this is not enough to

undermine the importance of contingency, even if it was not as high as Gould believed

(Sober 2003; Sterelny 2005; Szathmary 2005).

2.3 Explanatory Coherence in Evolution

It has been found that students may exhibit both alternative and scientifically acceptable

conceptions and bring different ones into play in response to different problem contexts

(Palmer 1999). Hence, it is important to investigate not only if students have accommo-

dated new concepts or a new explanatory framework, but also if they exhibit explanatorycoherence after instruction. In this context, exhibiting explanatory coherence means pro-

viding the same type of explanation to all tasks; in other words, thinking of all processes in

the same terms and explaining them by using the same type of explanation. This is based

on a theory of explanatory coherence proposed by Thagard (1989, 1992). According to this

theory, explanatory coherence can be understood as a relation between two propositions

which cohere if there is some explanatory relation between them. In particular, two

propositions P and Q cohere if they are analogous in the explanations they respectively

give of some R and S. On the other hand, two propositions are incoherent if they contradict

each other or if they offer competing explanations (Thagard 1992, pp. 6465). This theory

has been applied to Darwins theory itself to conclude for its explanatory coherence.

Darwins explanations are based mostly on two hypotheses, branching evolution and

natural selection, which are not just co-hypotheses but were used to explain each other (the

latter to explain the former). This fact and the analogy between natural selection and

artificial selection increase the explanatory coherence of Darwins theory (p. 140).

This theory of explanatory coherence has been applied in earlier studies, concerning

young students views on the origin of species, from which different conclusions have been

drawn. In the first of these studies students (12-years old) were found to use internally

consistent explanatory frameworks (Samarapungavan and Wiers 1997). However, the other

study that involved students of several age groups (57, 810, and 10.512 years old)concluded that students explanations were not always consistent (Evans 2001). In a pre-

vious study that focused on 1415 year-old students explanations about evolution it was

found that they did not always provide the same explanations to tasks with different

content and hence did not exhibit explanatory coherence (Kampourakis and Zogza 2008).

Hence, it is interesting to investigate if students who have accommodated new explanations

are able to apply them consistently and if they exhibit explanatory coherence after

instruction. Students do not only need to accommodate new concepts but also to learn to

apply them consistently to different problem contexts.

2.4 Preliminary Evolutionary Explanations

In general, a scientific explanation consists of an explanandum (whatever is being

explained) and an explanans (whatever is doing the explaining). For example, if one asks

why X? and the answer is because Y, then X is the explanandum and Y is the explanans

(Godfrey-Smith 2003, p. 191; Rosenberg 2005, p. 26). In the philosophy of science there


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have been several views on scientific explanation; it has been suggested that to explain

something is: (a) to show how it is derived in a logical argument that includes a law in the

premises (covering law model: Hempel and Oppenheim 1948), (b) to give information

about how it was caused (causal account: Salmon 1984), and (c) to connect a diverse set of

facts by subsuming them under a set of basic patterns and principles (unification account:Kitcher 1981), or use a combination of the causal and the unification account (kairetic

account: Strevens 2004). The structure of evolutionary explanations has been described in

terms of all these accounts of scientific explanation: the covering law model (Rosenberg

2001), the causal account (Scriven 1959; Wright 1973), the unification account (Kitcher

1989), and the kairetic account (Strevens 2009). Despite the differences, it seems that there

is agreement among philosophers that the concept of cause is central to the process of

scientific explanation (Kitcher 1989; Salmon 1990; Godfrey-Smith 2003; Woodward 2003;

Strevens 2004; Rosenberg 2005).

When trying to identify causes in biology, one may ask two different types of questions:

(a) why something exists or how it has come into existence (Why? question) and (b)

how something operates or functions (How? question). These questions correspond to

two different types of causes: ultimate causes, which are related to the evolutionary history

of the species, and proximate causes, which are related to the physiology of the individuals

(Mayr 1961). This distinction, which has been considered as a major contribution to the

philosophy of biology (Beatty 1994), has been reconstructed to include a broader con-

ception of development (not only the decoding of a genetic program but also the causal

interactions between genes, the extra-cellular mechanisms and the environmental condi-

tions), and a broader conception of evolutionary causes (not only natural selection but also

migration, mutation, genetic recombination and drift). In this perspective two distinct kindsof explanations exist: (a) proximate explanations which are dynamical explanations for

individual-level causal events and (b) evolutionary explanations which are statistical

explanations that refer to population-level events (Ariew 2003).

To overcome students preconceptions and to achieve conceptual change and explan-

atory coherence in evolution a new explanatory framework was developed. The reasoning

in the Origin of Species (Darwin 1859) involved two central ideas: the tree of life and

natural selection. The first central idea involved two distinct ideas: transmutation, the idea

of one species changing into another and common descent, the idea of one species splitting

into two or more species. The other central idea, natural selection, offered an account of

how species changed (Waters 2003). However, these arguments have been given unequaltreatment in the philosophy of science with most accounts focusing on natural selection.

Since common descent and natural selection were two of Darwins central arguments,

students might first learn how to use them to provide explanations of homologies and

adaptations, respectively. Homologies (explanandum) may be explained through common

descent (explanans), as features that were possessed by a common ancestor that evolved by

splitting into multiple descendent taxa. On the other hand adaptations (explanandum) may

be explained by the evolution of species into new ones through natural selection (ex-

planans). We describe these types of explanation as preliminary evolutionary explanations

and we suggest that they should form the basis for teaching further about evolution.Evolutionary processes are very complex and involve many different concepts. We con-

sider preliminary evolutionary explanations as described above a minimal starting point for

teaching about evolution. Students should learn to explain the origin of traits in purely

naturalistic terms by correctly applying some major concepts of evolutionary biology. An

explanatory framework based on the explanation of homologies as the result of common

descent and of adaptations as the result of evolution through natural selection is expected to


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promote conceptual change in evolution and explanatory coherence because homologies

and adaptations would be attributed to particular causal, non-intentional, processes.

This new explanatory framework draws upon particular philosophical accounts of

explanation. In particular, the structure of explanations about the origin of adaptations was

based on the kairetic account of explanation (Strevens 2004, 2009) whereas the structure ofexplanations about the origin of homologies was based on the unification account (Kitcher

1989). This selection was made on the basis of the explananda (adaptations, homologies)

and the particular accounts of scientific explanation (kairetic, unification). Homologies are

commonalities between taxa that are brought together and hence unified in a particular

branch (or bunch of branches) of the phylogenetic tree that goes back to a common

ancestor. Thus, the unification account is useful because it highlights the common (uni-

fying) feature, which it also explains (Kitcher 1989, p. 443). On the other hand, adaptations

are traits that have been maintained through natural selection, because they provided an

advantage to their possessors, in a particular environment, and have thus contributed to

their survival. This advantage was a difference-making-factor; hence the kairetic account is

appropriate because it highlights these particular factors (Strevens 2009, pp. 333334).

Students were not taught in detail about the typical structure of each type of explana-

tion. However, the important features were highlighted in each case and this framework

was the guide for instruction. Students were instructed to explain similarities (the term

homology was not used) through common descent and special features (the term adaptation

was not used) through natural selection. In particular, students were taught to construct

explanations for homologies by referring to a common ancestor who possessed the features

that were common to the taxa discussed in the tasks. The general form of explanation they

were given for homologies was the following: to explain why species A and B share acommon feature H (homology), assume that a common ancestor C which possessed feature

H existed in the past and that both A and B descended from C. Students were taught and

practiced how to construct such explanations during teaching unit 5.5 (Table 1). Similarly,

the general form of explanation they were given for adaptations was the following: to

explain why species S possesses feature (adaptation) A, assume that S descended from an

older population that included both individuals that possessed feature A and others that did

not, as well as that this feature provided an advantage to its possessors in the particular

environment; as a result those individuals that did not possess A died whereas those that

possess A survived and evolved to species S. Students were taught and then practiced how

to construct such explanations during teaching unit 5.6 (Table 1). At first an example waspresented by the instructor and then they were given several tasks to which they had to

provide an answer (explanation). They were given a few minutes to write down their

thoughts and then these were presented and discussed in the classroom. Finally, students

were given some more tasks as homework, which were discussed at the beginning of the

next teaching unit. It should be noted that the tasks included in the questionnaire (see

Appendix 1) were not discussed in the classroom.

3 Method

3.1 General Overview of Methods

This study aimed at documenting students explanations after instruction, with the latter

having a focus on challenging their intuitive explanations and promoting a shift to evo-

lutionary explanations. A specific teaching sequence was developed that highlighted the


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idea of contingency in evolution, a concept expected to be in conflict with students

preconceptions which were previously documented (Kampourakis and Zogza 2008).

Instruction also aimed at providing a framework for constructing particular explanations, in

order for students to achieve explanatory coherence. An open-ended questionnaire was

used to allow students to express their own views on issues related to evolution, as well as

to provide detailed explanations. The questionnaire used in the previous study, during

which it was completed as a pre-test (September 2004), was also used to document stu-

dents explanations after instruction (April 2005). These explanations were analyzed and

compared both to each other as well as to the respective ones before instruction. Semi-

structured interviews were also performed with 15 students both before and after

instruction. We should note that our main aim was to investigate if the suggested

explanatory framework could be taught to lower secondary students and if it was effective,

and not if it was more effective than traditional instruction. Hence, the design of the

study did not include a control/comparison group that received a different type of

instruction e.g. one that lacked the emphasis on genetics.

Table 1 The teaching sequence, the teaching units and concepts-sources of contingency

Teaching themes Teaching units (45 min each) Concepts-sources

of contingency

1. Cell structureand function 1.1 Prokaryotic cellsbacteria1.2 Eukaryotic cellsanimal and plant cells

1.3 Activity 1: cell types and their size

1.4 Protozoa

1.5 Fungi

1.6 Activity 2: microscopy

1.7 Viruses

2. Cells and

the organism

2.1 Microbes and diseases

2.2 The human immune system (I)

2.3 The human immune system (II)

2.4 Immunization

2.5 Human blood groups

3. Ecology 3.1 Ecosystems

3.2 Biodiversity

3.3 Activity 3: study of biodiversity

in the school yard

Environmental changes

4. Reproduction

and inheritance

4.1 Human reproduction

4.2 The study of heredity (I)

4.3 The study of heredity (II)

4.4 Activity 4: chromosomes

4.5 Activity 5: phenotype and genotype

4.6 The structure of DNA (I)

4.7 The structure of DNA (II)

4.8 The flow of genetic information4.9 Activity 6: DNA extraction

4.10 Activity 7: human genetic diversity

4.11 Mutations

Random gamete sampling, mutation

5. Evolution 5.1 Activity 8: the finches beaks

(stage of conceptual conflict)

5.2 Geological time

5.3 Activity 9: measuring geological time

5.4 Evolution

5.5 Common descent and branching evolution

5.6 Differential survival and natural selection

Natural selection


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3.2 Participants

This study was performed in a private school in Greece, during a General Biology course.

Greek people are supposed to be quite religious however there are not many Christian

fundamentalists that oppose the teaching of evolution. In a pre-study performed a yearbefore the one presented in this paper, students attitudes towards evolution were inves-

tigated and no opposition was found. Hence, we did not think there was a need to address

students religious beliefs. When some students asked relevant questions, the instructor

always made the distinction between questions that can and those that cannot be answered

by science. The data presented were collected at the end of instruction, with an open-ended

questionnaire administered and completed within a single teaching hour. A group of 98

secondary students (3rd grade of Greek lower secondary school, 1415 years old) com-

pleted the written open-ended questionnaire (April, 2005). The first author was also the

instructor of the course. This was done in order to ensure that instruction would be done in

the same way for all students, who were divided into four groups.

3.3 Instruction

In order to help students overcome their preconceptions, two important conditions were

considered necessary to be fulfilled: (1) students should learn some basic biological con-

cepts in order to be able to understand complex processes like natural selection and (2)

students should be brought to a kind of a conceptual conflict situation, where major

components of their conceptual frameworks would be challenged. To satisfy these con-

ditions we developed a teaching sequence during which students were taught about theseveral levels of biological organization (cells, organisms, ecosystems) and then about the

mechanisms of heredity and of the origin of genetic variation. Then, all these concepts

were used to teach about evolution. It is important to note that in order to understand

evolution, students need to build a complex conceptual framework and be able to move

from micro-concepts (e.g. alleles) to macro-concepts (e.g. species) and vice versa. The

language of instruction was Greek, which is the primary language in this setting. Teaching

was performed in a classroom setting were a slide projector was available.

Each teaching unit lasted 45 min and was performed in a constructivist perspective. This

means that students did not just attend lectures given by the instructor. On the contrary,

classroom discussion and interaction between the teacher and the students as well as amongstudents was encouraged. The whole course begun by documenting students preconceptions

about evolution (these are described in a previous paper; Kampourakis and Zogza 2008).

These preconceptions were explicitly addressed during teaching units 5.45.6. In each

teaching unit, slides were shown by the instructor related to the respective theme taught.

Students were asked to comment on the first slides they saw and recall their previous

knowledge of the organisms or the phenomena presented. Thus, particular preconceptions

known from the literature were implicitly addressed during particular teaching units (e.g.

inheritance of acquired characteristics during teaching unit 4.2see Table 1). This being

said, it does not mean that this interaction was always successful, because in several cases

students knew nothing about what they were shown. In these cases, instruction proceeded by

building on students previous knowledge to help them develop an understanding of the

concepts taught. Students were also given a booklet containing a printout of the slides, so that

they were able to take notes of what it was discussed during instruction. All relevant infor-

mation was included in the textbook used, which was provided by the National Ministry of

Education. The teaching units as well as time frames are presented in Table 1.


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On the other hand, in order to satisfy condition 2 emphasis was put on two concepts

entirely opposed to childrens preconceptions described above: chance and unpredict-

ability. Since many students perceived evolution as a goal-directed process and provided

teleological explanations (Kampourakis and Zogza 2008), it was made explicit that this is

not how evolution proceeds and that unpredictability is an important feature of the evo-lution of life on earth. Instruction focused on the role of chance in the evolutionary process,

in order for students to understand that many important events are unpredictable: (a) which

new genetic variations may arise in a population, (b) which gametes of those available in

each generation will fuse to produce the offspring, (c) which proportion of a population

may migrate to an unoccupied niche, and (d) which environmental changes may take place

in an ecosystem. Hence, a specific activity was developed for lower secondary school

students (Kampourakis 2006) in order to teach effectively about the major steps of the

evolutionary process: the origin of new variation and natural selection (activity 8 in

Table 1). This is a simple pencilpaper activity that helps students recognize by them-

selves that intra-specific variation and differential survival depending on the environment

are two important components of the evolutionary process. Before this activity, students

had already been taught about the structure and function of cells, organisms and ecosys-

tems and they had studied basic principles of genetics (Table 1); hence the activity was

expected to make them combine their previous knowledge and build their own under-

standing of how evolution proceeds.

3.4 Data Collection

Five different tasks were developed and were included in the open-ended questionnaire.All assessment items were written in Greek. Students explanations were translated by the

first author and translations were checked by the second author of this paper. Although we

were aware that the species context is important (for example it is interesting to compare

students explanations to tasks referring to the same species or their explanations to tasks

referring to animals with those referring to plants), we did not use the same species in all

tasks in purpose. We thought that if we referred to the same species to some or to all tasks,

students might use their explanation to an easy task in order to construct their expla-

nation for a more difficult task (easy and difficult have to do with how students

would think of the tasks; the same tasks might seem easy to one student and difficult to

another). Hence, we referred to different species in each task so that students wouldconstruct their explanations for each task independently (as far as this could be possible).

In other words we did not want to make explicit that these tasks were somehow related so

that we could see how different the explanations to the several tasks would be.

There were basically two types of tasks (see Appendix 1): those which referred to

homologies and demanded explanations based on common descent (tasks 1 and 5) and

those which referred to adaptations and demanded explanations based on natural selection

(tasks 2, 3 and 4). It has been shown that students perceive tasks with different content

differently and, although the same type of explanation may be required, they might explain

the existence of particular traits in different terms. In tasks 1 and 5 the difference was only

on the level of reference (species and cell, respectively). Before instruction students had

explained similarities between different species more accurately, as a result of their being

more familiar with them, than similarities between cells, a level of organization they had

not previously studied in much detail. On the other hand, in tasks 2, 3 and 4 the difference

was that students were given different kinds of information on which they could base their

explanations. Before instruction it was found that the more was the information students


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were given, the more were the evolutionary and the less the teleological explanations they

provided (Kampourakis and Zogza 2008). Table 2 summarizes the levels of reference and

amount of information available for each assessment task. The questionnaire was com-

pleted after instruction (April 2005) and the objective of the study was to provide an in-

depth analysis and an overall description of students explanations about evolution.

In order to find out if students were aware of the concept of common descent or if they

might be able to explain the homologies between species based on common descent, two

tasks were included in the questionnaire in order to document this in two distinct levels: (a)

the species level (task 1) and (b) the cellular level (task 5). In particular, students were

asked to explain the similarities (morphological and physiological) observed among the

dogs, the wolves and the foxes (task 1) and the fact that all organisms consist of one or

more cells that, and that, despite their other differences, they all contain DNA, ribosomes

and cellular membrane (task 5). In both cases homologies were the explanandum, and themajor difference between the two tasks was the level of reference (species and cell,

respectively). We should note that although these tasks referred to homologies, this term

was not explicitly mentioned and reference to similarities was made instead.

On the other hand, in order to find out if students were aware of the concept of natural

selection or if they might explain adaptations as the result of the differential survival of

individuals of the same species that exhibited different traits and to the maintenance of

these traits through reproduction, three tasks were included in the questionnaire in order to

document this in three levels: (a) given no information about the initial state of the

evolutionary process (task 3), (b) given information about the initial state but without

details about the existence of intra-specific variation and of a natural selection factor (task2), and (c) given information about the initial state with details about the existence of intra-

specific variation and of a natural selection factor (task 4). We should also note that

although these tasks referred to adaptations, this term was not explicitly mentioned.

Semi-structured interviews were also performed with 15 students both before and after

instruction. Interviews performed before instruction aimed at providing an in-depth anal-

ysis of their intuitive explanations (Kampourakis and Zogza 2008). On the other hand, we

also performed interviews a year after instruction (March 2006) with these 15 students in

order to have both a retention test and a meta-cognitive test. Hence, we wanted to

investigate if students explanations a year after instruction were different than those they

had provided to the post-test. To do this we used a questionnaire that was similar to the

written one, with each task of the retention test being equivalent to a task of the written test

(with the exception of the last task that remained as it was; see Appendix 2). Moreover,

during these interviews students had the chance to compare their explanations between the

several tests. Especially those who had provided evolutionary explanations to all tasks both

in the post-test and in the retention test were encouraged to reflect on the factors that made

Table 2 The levels of reference

and amount of information

available for each assessment

task

Task Levels of

reference

Amount of information

available

1 Species Final state

2 Species Final state, initial state3 Species Final state

4 Species Final state, initial state,

intra-specific variation,

natural selection factor

5 Cells Final state


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them achieve this. Similar responses were given by all students that provided evolutionary

explanations to all tasks both in the post-test and in the retention test. Hence, through this

meta-cognitive analysis we managed to identify a potential factor that influenced students

shift from their intuitive to evolutionary explanations.

3.5 Data Analysis

In an older study on students explanations How? was related to the mechanism or cause

responsible for the change and Why? to the rationale that could be used to explain the change

(Abrams et al. 2001). In our study, we considered Why? questions, such as Why did trait A

originate? or Why did trait B change to trait A? to refer to the evolutionary cause that

produced trait A or changed B to A. On the other hand, we considered How? questions, such

as How did trait A originate? or How did trait B change to trait A? to refer to the

mechanism of change. The tasks used in our study demanded evolutionary explanations, as

students were asked to explain the origin of homologies and adaptations. Hence, we would havebeen expected to use Why? questions. However, as it has been found that students tend to

give teleological explanations to causal questions (Southerland et al. 2001), we selected not to

use the word why, in order to diminish the number of teleological explanations, and to ask

students to provide explanations for the mechanism of the change by using the word how

instead. We expected that through the description of the mechanism responsible for the change,

the evolutionary cause of this change would be identified.

In order to explain a particular change or the existence of a particular trait one might try to

identify three different types of causes: (a) evolutionary causes, (b) proximate causes, and (c)

final causes. The explanations based on each type of causes are described as (a) evolutionary,

(b) proximate, and (c) teleological, respectively. In the case of evolutionary causes expla-

nations are based on population-level events that took place in the past and belong to the

evolutionary history of the species. Evolutionary explanations make use of concepts such as

common descent and natural selection. In the case of final causes explanations are based on

the fulfillment of a purpose or a desired goal. Thus, teleological explanations explain the

presence of particular body structures and functions to respective purposes or intentions.

Finally, in the case of proximate causes explanations are based on individual-level events and

on the present developmental and physiological characteristics of organisms.

All students explanations were coded into three categories: evolutionary, proximate

or teleological, depending on the cause responsible for the origin of trait (evolutionary,proximate or final, respectively). In particular, explanations that referred to the past, to the

existence of a common ancestor or to features that existed in older species as well as to

population level events (e.g. processes of change) that resulted to what was being described

in the tasks of the questionnaire, were coded as evolutionary. Explanations that referred to

a plan, a purpose or a goal were coded as teleological, both when they referred to popu-

lation-level events and to individual-level events. Explanations that referred to individuals

and to how they might have been influenced and changed were coded as proximate. In this

study, the category of proximate explanations forms a category wider than the corre-

sponding philosophical one in order to include all non-evolutionary explanations, meaning

all those explanations that make no reference to either common descent or differential

survival and mostly involve individuals and not populations, as well as all non-teleological

explanations. All explanations referring to crosses between individuals from different

species, to the influence of the environment on individuals as well as to the effect of use

and disuse on individuals were included in this category. This was done because these

explanations neither made reference to the past, or to populations, as evolutionary


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explanation do, nor to the future as teleological explanations do. All cases in which unclear

or no explanations were provided were included in a no explanation category. Coding of

students explanation was performed independently by both authors, until absolute

agreement was achieved.

Statistical analysis of the results was performed by both authors. For statistical analysisthe Wilcoxon test was applied in order to simultaneously compare the frequencies of all

four categories. The Wilcoxon test demands a hierarchical categorization of the variables

(e.g. 14). Hence, although they are not hierarchical the categories were used hierarchi-

cally in our analysis; we used a categorization from the category of the most accurate (1) to

the category of the least accurate explanations (4) as follows:

evolutionary explanations: 1 (since the tasks described evolutionary processes,

evolutionary explanations were considered as the most appropriate type);

proximate explanations: 2 (proximate explanations are insufficient to explain evolu-

tionary processes, however they are naturalistic explanations and as such more accuratethan teleological explanations);

teleological explanations: 3 (teleological explanations are unnatural or supernatural

explanations that are not at all appropriate);

no explanations: 4 (in this study we considered even teleological explanations as a better

option than not providing an explanation, or providing explanations that were not clear).

3.6 Research Questions

By analyzing students explanations to the aforementioned tasks, we were actually lookingfor answers to the following research questions:

How many students provided the same type of explanation to tasks 1 and 5, 2 and 3, 2

and 4, 3 and 4 after instruction? Were there any significant differences between the

types of explanations that students provided to these pairs of tasks? In which task more

evolutionary explanations were given?

How many students provided the same type of explanation to all tasks? Can students

achieve explanatory coherence in evolution after instruction? In this context, achieving

explanatory coherence means providing the same of type of explanation to all tasks, by

thinking of all processes in the same terms and by explaining them by using the sametype of causes in the explanans (evolutionary, proximate or final).

4 Results

In several explanations evolutionary concepts such as common descent and natural

selection were correctly used. However, many students provided teleological explanations

even after instruction, and in some cases they provided different explanations depending on

the content of the task as was the case before instruction. Examples of the four types of

explanations to tasks 15 in the questionnaire after instruction are presented in Table 3.

4.1 Students Conceptual Change from Intuitive to Evolutionary Explanations

The application of the Wilcoxon test resulted to a statistically significant difference between

students explanations to task 1 before and after instruction (p\ 0.001). Although many


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Table 3 Examples of students evolutionary, proximate and teleological explanations to given to tasks 15

Task Type of

explanation

Examples of students explanations

in the questionnaire (S: student)

1 Evolutionary S60: It is obvious that all three species are descended from a common ancestor.Individuals from populations of the ancestral species might have been isolated and

to these isolated populations mutations might have taken place that produced these

features These mutations and the respective features they produced were restricted

to each particular population (since they were isolated) and gradually new species

were formed

Proximate S86: This can be explained by the fact that all species are descended from the wolves

and may have come up from intercrosses and that is why they exhibit similarities

Teleological S5: It seems that these organisms are descended from the same Paleolithic organism.

But each one underwent specific changes, according to the peculiarities of the

environment to which he had to adapt, in order to survive

2 Evolutionary S70: In earlier times, giraffes with shorter necks used to exist. Mutations took place

accidentally. Hence, variation existed and some giraffes still possessed short neckswhereas others possessed longer necks. As time went by, only those with the longer

necks could survive because they feed from the taller trees, while all other animals

were feeding from the ground. Obviously this is how the initial ones gradually

disappeared

Proximate S67: I believe that due to infections, drought etc. there was adequate food on the

ground, hence while giraffes were trying to browse on the leaves from the trees, their

neck was lengthened because their body could not grow up any more. I believe that

this can happen with every organism, when you try to achieve something, you finally

make it as time goes by

Teleological S15: some natural mutations just occurred in order to reach the leaves of the trees

because the food on the ground was not so good. Only those animals to which the

mutations took place managed to survive

3 Evolutionary S62: They obtained these features after some accidental mutation in their genes. This

mutation provided an advantage to their survival under the particular environmental

conditions. Thus, in these places more of them survived. It did not happen

purposefully in order to prevent them from going extinct. Those that accidentally had

an advantage simply survived

Proximate S77: In my opinion this is due to the environment. Each organism gets the features of

the environment in which it has grown up

Teleological S49: They obtained these features in order to be protected from the threats that emerge

in their environments

4 Evolutionary S95: The brown beetles emerged from mutations and started to reproduce and to

increase in number. The birds could spot the green beetles more easily while the brownones had the ability to conceal. This ability helped them survive while the green

beetles did not make it as they were all eaten by the birds

Proximate S64: They might have eaten a large quantity of green leaves and something changed in

their physiology and they all became green

Teleological S90: The color of the beetles changed due to a mutation in order to be able not to be

spotted easily by their predators and avoid extinction

5 Evolutionary S14: All organisms are descended from a common species, probably unicellular, that

possessed genetic material, ribosomes and cellular membrane. During evolution,

individuals of the initial species started to differentiate from each other, due to

mutations, and after they were isolated from the initial species, they formed new ones.

Hence, from a single organism that existed in the past, we were led to the enormous

diversity of species on earth

Proximate S41: Similarities are due to the fact that they are all organisms, thus they possess the

same features because that is the way their structure is

Teleological S91: Without cells there is no organism Ribosomes make proteins. Cellular

membrane protects them form enemies The genetic material controls cellular

processes. All these features are needed


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students (40) had provided evolutionary explanations to this task before instruction, their

number increased further after instruction (59). On the contrary, the number of students who

provided teleological explanations had decreased from 22 in the pre-test to 11 in the post-

test. Similar results were obtained for task 5. Although initially 21 students had provided

evolutionary explanations to task 5, this number increased further in the post-test to 51. Onthe contrary, there was a decrease in the number of the teleological explanations (23

compared to 63 in the pre-test). The fact that 23 students gave teleological explanations

even after instruction is probably due to their difficulty to apply evolutionary concepts at the

cellular level. The application of the Wilcoxon test resulted to a statistically significant

difference between students explanations to task 5 before and after instruction (p\ 0.001).

Similar results were obtained for the other tasks. The application of the Wilcoxon test

resulted to a statistically significant difference between students explanations to task 2 before

and after instruction (p\ 0.001). Although only two students had initially provided an

evolutionary explanation to the task, the number of evolutionary explanations increased to 63

after instruction. In addition, there was a decrease in the number of teleological explanations

after instruction (10 compared to 52 in the pre-test). The explanations provided to task 3

formed the most interesting case of all. Although there was an increase in the number of

students who provided evolutionary explanations to task 3 after instruction (44 compared to 2

before instruction), their number was smaller than the number of evolutionary explanations

provided to the other tasks. This is probably due to the content of the task and the kinds of

available information. On the other hand, the number of teleological explanations to this task

decreased from 70 in the pre-test to 31 in the post-test. Although this is a considerable

decrease, it is particularly interesting that approximately one-third of the students provided

teleological explanations to this task even after instruction. The application of the Wilcoxontest resulted to a statistically significant difference between students explanations to task 3

before and after instruction (p\ 0.001). Finally, among those tasks that referred to adapta-

tions (tasks 2, 3, 4), task 4 was the one to which most evolutionary explanations were provided

in the pre-test (39), probably due to the kinds of the available information (see Table 2). This

number increased even more (80) in the post-test. Moreover there was a considerable

decrease in the number of students who provided teleological explanations to task 4 after

instruction (6 from 30 in the pre-test). A conclusion that can be drawn is that the kinds of the

available information diminished the need for teleological explanations. The application of

the Wilcoxon test resulted to a statistically significant difference between students expla-

nations to task 4 before and after instruction (p\0.001).From all the above it is obvious that in all cases there were statistically significant dif-

ferences between students explanations before and after instruction. This result shows the

effectiveness ofpreliminary evolutionary explanations for students conceptual change from

intuitive to evolutionary explanations at the age of 1415 years old. The increase or decrease

in the number of each of the several types of students explanations, after instruction is

presented in Table 4.

Table 4 Change in the number of each type of explanation after instruction

Type of explanation Task 1 Task 2 Task 3 Task 4 Task 5

Evolutionary 40?59 2?63 2?44 39?80 21?51

Proximate 18?26 21?19 7?13 8?7 2?5

Teleological 22?11 52?10 70?31 30?6 63?23

No explanation 18?2 23?6 19?10 21?5 12?19


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Students individual scores are presented in Table 5. Those students that exhibited a shift

from their previous explanations to evolutionary explanations were included in the category

gain (E), suggesting that they gained what instruction aimed at: learn how to provide evo-lutionary explanations. The other category gain (O) includes those students that exhibited a

positive shift to other types of explanation (e.g. from teleological to proximate explanations).

On the other hand those students that gave evolutionary explanations both in the pre-test and

the post-test were included in the category no change (E), whereas those that gave any other

type of explanation both in the pre-test and the post-test were included in the category no

change (O). Finally, those students that performed worse in the post-test (e.g. provide a

proximate or a teleological explanation in the post-test while they had provided an evolu-

tionary one in the pre-test) were included in the lostcategory (see Table 5).

It should be noted that those students who were interviewed a year after instruction and

provided evolutionary explanations to all five tasks (Appendix 2) considered mutations and

the teaching about the role of chance and unpredictability in evolution as the major factors

that made them reject their preconceptions and replace their intuitive explanations with

evolutionary ones. For example, a female student (S14) who had provided a proximate

explanation to task 1 and a teleological to task 3 in the pre-test and who provided evolutionary

explanations to all tasks both in the post-test and in the retention test made the following

comment: During instruction [] I realized that organisms cannot change in the course of

their life due to some need, e.g. to have the trunk of an elephant lengthened, and I also realized

that it would make more sense if these changes occurred due to random mutations []Needis

insufficient to explain [change] and I believe that [] there may be a particular need but it isnot certain that organisms will manage to satisfy it. The student was then asked explicitly

what was the crucial factor that made her change her mind and she answered that the mutated

organisms, depending on their environment [] survived, whereas the others vanished [].

The student was then asked if she still found mutation- based explanations more plausible

than purpose-based explanations and why this was case. She responded that: Since we

learned that mutations do happen in genes, and since this is an event in which we cannot

interfere, I find this explanation satisfying. That mutations take place by chance and then

influence survival. Our view that teaching about mutations and heredity was crucial for

students understanding is based on such comments in our meta-cognitive test.

4.2 Students Explanations and Explanatory Coherence After Instruction

More than half of the students explained the similarities among species or among cells with

appeal to the idea of common descent. Students explanations to tasks 1 and 5 after

instruction are presented in Table 6.

Table 5 Individual scores in the various tasks after instruction

Task 1 Task 2 Task 3 Task 4 Task 5

Gain (E) 32 61 42 47 32

Gain (O) 13 13 18 5 8No change (E) 27 2 2 33 19

No change (O) 9 17 25 4 22

Lost 17 5 11 9 17

Total 98 98 98 98 98

E stands for evolutionary explanations and O stands for all other types


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From the results presented in Table 6 it is obvious that students provided different

explanations to tasks 1 and 5 after instruction. Despite the fact that 59 students provided

evolutionary explanations to task 1 compared to 51 students to task 5, there were differ-

ences in the numbers of the other types of explanations. Thus, 26 students provided

proximate explanations to task 1 compared to 5 to task 5. Finally, the students who

provided teleological explanations based on the organisms needs to task 5 were manymore (23 students) than to task 1 (11 students). The application of the Wilcoxon test

resulted to a statistically significant difference between students explanations to tasks 1

and 5 after instruction (p\ 0.001). Although emphasis was put on the concept of common

descent during instruction for the explanation of similarities (homologies) both at the

species and at the cellular level, several students provided either proximate or teleological

explanations to tasks 1 and 5 in the post-test. However, it is interesting that among those

more students provided proximate rather than teleological explanations to task 1 while

more students provided teleological rather than proximate explanations to task 5. It seems

that for those students who did not thoroughly understand the concept of common descent,

it was possible to construct explanations based on the physiology and the function oforganisms (task 1), but not of cells (task 5) for which more teleological explanations were

given. This difference could be probably due to fact that students were more familiar with

the physiology of organisms rather than with the properties of cells.

Similar results were obtained for the other three tasks. Many students provided

explanations with features of a natural selection process to these tasks after instruction.

Students explanations to tasks 24 are presented in Table 7. One interesting finding is that

the number of teleological explanations gradually diminished from task 3 towards task 2

and then 4. Given the fact that more information was given to students in task 4 compared

to task 2, in which in turn more information was given compared to task 3, it seems that the

number of the teleological explanations depended on the kinds of information relative to

the task given to students. In particular, the less was the information given to students, the

larger was the number of teleological explanations they provided. This finding may show

the tendency of students to look for purpose or plan when they do not have adequate

information. This tendency may be the outcome of particular psychological intuitions

about purpose and design, that make them see the world in teleological terms, which

Table 6 Students explanations

to tasks 1 and 5 categorized as

evolutionary, proximate and

teleological

Type of explanation Task 1 Task 5

Evolutionary 59 51

Proximate 26 5

Teleological 11 23

No explanation 2 19

Total 98 98

Table 7 Students explanations

to tasks 2, 3 and 4 categorized as

evolutionary, proximate and

teleological

Type of explanation Task 3 Task 2 Task 4

Evolutionary 44 63 80

Proximate 13 19 7

Teleological 31 10 6

No explanation 10 6 5

Total 98 98 98


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emerge early in childhood and may persist even to adulthood. One possibility is that young

children have an early sensitivity to intentional agents and their behavior as intentional

object users and makers. The subsequent development of a teleological bias to explain all

kinds of phenomena in terms of a purpose might occur because students draw on their earlyknowledge of human intentional behavior. As a result, in the absence of other explanations,

they treat objects of all kinds as artifacts that have been intentionally designed (Kelemen

1999). On the other hand, the more was the information given on the task, the larger was

the number of proximate and evolutionary explanations. The number of proximate

explanations increased when students were given the initial and the final state of the

evolutionary process. Finally, evolutionary explanations were much more in task 4 where

students were given additional data such as the intra-specific variation and the natural

selection factor. All the above is summarized in Table 8.

In particular, there was a difference in the types of explanations provided by the stu-dents to tasks 2 and 3 after instruction. More students provided evolutionary explanations

(63 to task 2 and 44 to task 3) rather than teleological (10 to task 2 and 31 to task 3) to

these tasks. The application of the Wilcoxon test resulted to a statistically significant

difference between students explanations to tasks 2 and 3 (p\ 0.001). The fact that less

teleological and more evolutionary explanations were given to task 2 compared to task 3,

was probably due to the different content of the tasks (see Table 8). It is possible that

students perceived the features under discussion as having a different adaptive significance

for the organisms which possessed them. Perhaps the coloration of the body that provides

concealment was more easily explained in teleological terms than the change in the length

of the giraffes neck. Hence, even after instruction, many students explained concealmentin teleological terms; a natural explanation did not seem to be adequate for many students.

The comparison of students explanations to tasks 3 and 4 is particularly interesting

because they provided different kinds of information about each evolutionary process, but

they both referred to the coloration of the body that provided concealment in a given

environment. More teleological explanations and less evolutionary explanations were

given to task 3 compared to task 4. In particular, 6 students provided teleological expla-

nations to task 4 compared to 31 to task 3 and 80 students provided evolutionary

explanations to task 4 compared to 44 to task 3. The application of the Wilcoxon test

resulted to a statistically significant difference between students explanations to tasks 3

and 4 (p\ 0.001). As shown in Table 8, students were aware of only the final state of the

evolutionary process described in task 3, while more relevant information was available in

task 4. Consequently, even after instruction 31 students provided teleological explanations

to task 3, although many of them had provided evolutionary explanations to the other tasks.

The comparison of students explanations to tasks 2 and 4 differs from the previous one

in that both the initial and the final state of the evolutionary process were given in task 2.

Table 8 The number of explanations provided to tasks 2, 3 and 4, accordingly with the information given

in each task, after instruction

Task Relevant information given Type of explanation

Teleological Proximate Evolutionary

3 Final state 31 13 44

2 Final state, initial state 10 19 63

4 Final state, initial state, intra-specific

variation, natural selection factor

6 7 80


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Thus, we tried to find out if this additional information (the initial state of the evolutionary

process given in task 2 but not in task 3) might diminish the number of teleological

explanations. The additional information made students provide more proximate expla-

nations to task 2, compared to tasks 3 and 4. Students who provided evolutionary

explanations to task 2 were 63 compared to 80 to task 4, while few teleological expla-

nations were given to both tasks (10 to task 2 and 6 to task 4). The application of the

Wilcoxon test showed that there was a statistically non-significant difference betweenstudents explanations to tasks 2 and 4 (p = 0.042). It seems that when the initial state of

the evolutionary process is available, students may more easily provide evolutionary

explanations rather than teleological ones.

The statistical analysis of students explanations to tasks 15 after instruction resulted to

statistically significant differences in most cases. Hence, at first sight it seems that the

teaching of preliminary evolutionary explanations was not efficient in assisting students

achieve explanatory coherence in evolution, since they provided different types of

explanations to the tasks. However, a more careful examination of the results shows that

this may not be the case. After instruction 28 students provided evolutionary explanations

to all five tasks, compared to 2 before instruction (Table 9). Hence, although in general

students did not provide the same type of explanation to all tasks, there was an increase in

the number of those who did that after instruction. This fact shows the potential effec-

tiveness of preliminary evolutionary explanations for explanatory coherence in evolution.

We should note that it would be too ambitious to expect that after a single teaching

sequence all students would have been able to overcome their preconceptions and provide

evolutionary explanations to all tasks. Hence, the fact that almost one-third of the par-

ticipants achieved this is considered a satisfactory outcome.

5 Conclusions

This study aimed to provide a framework for understanding the nature of students bio-

logical explanations, as well as particular recommendations for teaching about evolution.

The framework was developed on the basis of the conclusions of research in teaching and

learning evolution, of the theoretical background in conceptual change and explanatory

coherence, of the historical and philosophical analysis of evolutionary explanations, as

well as on a previous study of secondary students intuitive explanations (Kampourakis and

Zogza 2008). In general, instruction on preliminary evolutionary explanations was found to

be effective in terms both of conceptual change and of explanatory coherence in the post-

test. The results of this study suggest that preliminary evolutionary explanations can form a

minimal explanatory framework for evolution in lower secondary school and a basis for

future evolution instruction.

Given that most of the earlier studies have involved secondary school or older students,

we considered more interesting to investigate students understanding of evolution at the

Table 9 Explanatory coherence

to tasks 15 before and after

instruction

Explanatory

coherence

Explanatory

incoherence

Total

Before 2 96 98

After 28 70 98Total 30 166 196


123


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lower secondary school level. It has been suggested that adults resistance to scientific

ideas may derive from assumptions and biases that originate early in childhood and that

may persist into adulthood. Both adults and children have been found to resist acquiring

scientific information when it clashes with their intuitions about the world (Bloom and

Weisberg 2007). Hence, perhaps the earlier these preconceptions are challenged, the moreeffective any science instruction will be. As students grow older and develop their personal

worldviews, any accommodation of scientific information that contradicts their beliefs or

views will be particularly difficult to achieve. However, this may not be the case with

younger students who may be more receptive and willing to accommodate new knowledge

as they are still in the process of developing their own worldviews. Our results suggest that

evolution instruction can be quite effective with students 1415 years old. It may be the

case that this instruction could facilitate any future evolution instruction but this requires

further research.

Given the post-test results that we obtained (Sect. 4.1) it seems that the emphasis put on

genetics during instruction can promote conceptual change in evolution. Our meta-cog-

nitive analysis suggests that it is important to put emphasis on the role of chance in the

evolutionary process and on the unpredictability that results from several specific con-

tingencies. Those students who understood that evolutionary outcomes depend on

particular events with unpredictable consequences, such as mutation and random gamete

sampling, realized why evolution is incompatible with the idea of purpose and design in

nature. Our results suggest that chance and unpredictability in evolution are important

factors that may make students reject their preconceptions and replace their intuitive

explanations with evolutionary ones; this is something that has not been given the required

attention in the relevant literature and needs to be investigated further. Hence, in order topromote conceptual change in evolution teachers might consider focusing instruction on

the role of chance and unpredictability in the production of new genetic variation. The

effectiveness of such an instruction stems from the fact that these concepts are totally

incompatible with intuitive teleology and ideas about plan and purpose in nature. A crucial

stage of instruction was when teaching about mutations. Students usually consider muta-

tions as harmful events; hence it is required that they are explicitly taught that mutations

are the cause of the production of new alleles within a population, as well as that this is

happening in an unpredictable manner, totally unrelated to the survival of the organisms.

Thus, they can then realize that the actual emergence of new variation in the population is

at odds with their intuitions about design. Then, they can implicitly be taught how thismechanism works and promotes evolutionary change in nature through activities, specif-

ically designed for this purpose (e.g. Kampourakis 2006). That was the stage of conceptual

conflict in the teaching sequence on used in this study. During the activity, students also

had the opportunity to realize that not only mutations but also sexual reproduction and

environmental changes may have unpredictable outcomes. Moreover, they were able to

distingu

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