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8/14/2019 Ideas premilinares sobre Evolucin.Secuencia de actividades
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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]
123
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
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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
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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
K. Kampourakis, V. Zogza
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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
Preliminary Evolutionary Explanations
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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