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1. Title:
Facilitating the teaching of the theory of evolution by enriching the teaching
of evidences for evolution with an epistemological perspective on relevant
distinctions and relations between facts and theories
2. Authors and institutions:
Gergely, Kertész, PhD Student, HPS Department at the
Budapest University of Technology and Economics (BME)
Hungary, Budapest, H-1111 Stoczek u. 2. St. Fsz.15.
[email protected]
Violetta, Léner, Biology-Chemistry Teacher
Kürt Foundation High School
3. Abstract:
The module is designed for four lessons (4x45 min). As opposed to prevailing textbook
practice the module attempts to incorporate epistemic issues and some basic NOS (Nature
of Science) issues into the teaching of evidences for evolution. Because in the last decade
evolutionary theory faces new attempts of invalidation by different religious and
antiscientific groups and surveys on scientific literacy have shown that much of what
students and the lay public know about evolution is erroneous or full of misunderstandings,
finding more efficient ways of teaching it became vital. To be able to realize a conceptual
change strategy in teaching evolution the module relies on prior student knowledge and
intuitions as resources for a more effective approach.
In traditional biology curricula, evidences for evolution are usually presented as a list of
items to be studied and no explanation is provided on the relation between the theory and
the facts. This statement not only true in Hungary, but it befits the traditional textbook
practice of Anglo-Saxon countries. This kind of treatment results in a shallow understanding
of the theory itself and the reasons behind its acceptance.
This module attempts to reach a clearer and deeper understanding of the classical
arguments for common descent by highlighting some epistemologically important relations
between facts and theories in the discussion of the topic. Examples and narratives from the
history of biology and perspectives form the philosophy of science are used to achieve this
goal. One novelty of the module is that it focuses on the less discussed theory of common
descent as a basic component of evolutionary theory. Another is the use of the original
Darwinian or Whewellian way of argumentation for evolution, the so called consilience of
inductions. In most textbooks, the evidences for evolution are simply listed as equally
important and independent facts in support of evolutionary theory. In the present module
through the historical discussion of biological theorising the relations and the importance of
the different facts is also clarified.
The module is still under evaluation. The present results can only be evaluated in a
qualitative way.
Keywords: evidences for evolution, common descent, history of science, philosophy of
science, NOS
4. Description of Case Study:
The aim of the module is twofold. One is to promote a better understanding of NOS
issues. The other is to facilitate the deeper understanding of the structure of the theory of
evolution. The second goal is achieved by the thorough clarification of the theory of
common descent as it lies at the basis of all theories of evolution form Lamarckism to the
neo-Darwinian theory (see Sober 1999, Cherif & Adams & Loehr 2001). The module might be
used in itself as an introductory module before the teaching of population genetics and
modern synthesis, but it has a second also autonomous part worked out as a separate
module, which focuses on the mechanisms of evolution. The present module helps students
to understand the exact role of observations about existing species and fossils in
evolutionary theory.
Teaching NOS is an important pedagogical challenge for today’s science education. The
major problem with current treatments of NOS in the classroom is the separation of the
philosophical views from historical insights, and often from the scientific content itself. The
discussion on methodology is often restricted to oversimplified logical arguments especially
when the teaching of NOS starts with epistemic considerations in themselves, out of context.
This practice goes against the lifelike treatment of these questions, where the relevant
epistemic criteria can be introduced as solutions for scientifically relevant problems and also
as argumentative devices in debates. In contrast to this practice, historically rich approaches
to science instruction allow for the natural introduction of scientific knowledge as something
in the need of justification, as something changeable, tentative and debatable.
To overcome the mentioned problems this module embeds the teaching of
epistemological considerations into a quasi-historical narrative on the development of
biological theories in the 19th century (for similar approaches see: Jensen & Finley 1997).
The narrative is constructed in a way that helps the teachers to highlight the
epistemologically important aspects of the theory of common descent and to shed light on
the reasons behind the acceptance of the theory by most biologists before the middle of the
19th century. So, the epistemic considerations are not shown as decontextualised, abstract
criteria, but rather as the results of a historically contingent development that gave rise to a
new science with special kinds of problems and solutions under the name of biology as JeanBaptiste Lamarck started to call it at the beginning of the 19th century.
The module also emphasizes the importance of student participation and group work. In
some phases of the module, students are asked to participate in the guided reinvention of
some parts of the theory in question. This helps to develop a stronger engagement with the
studied field.
Because the module applies a conceptual change strategy to science instruction it
requires that instructors have a detailed view of their students' prior knowledge of the topic
of evolution, therefore a lesson before the first lesson it is necessary to survey student
knowledge by a questionnaire of some sort.
The general strategy of this approach lies in the way the topics are introduced for the
students. There is always a phase where their initial intuitions, ideas regarding the actual
question are challenged by evidence for which they do not have adequate explanations or by
alternative theories which might also be good candidates for a presented problem. After
that, new ideas are presented to dissolve the dissatisfaction created by the challenges. In the
last phase the module helps students in experiencing the success of seeing that the new
ideas provide better explanations. (see: Smith 2009)
It is widely recognized in the field of educational research (e.g. van Dijk & Reydon 2009)
that the deeper understanding of the naive or folk knowledge regarding scientific themes
that students bring into the classroom is an important factor for realizing the aim of
providing a better understanding of scientific concepts. For the specific topic of biological
evolution, much research has already been undertaken to uncover the typical schemes and
the cognitive biases toward these schemes. Typical obstacles for understanding evolutionary
mechanisms appropriately are the well-known intentional and/or teleological, "need"
interpretations of adaptation as a process.
The less recognized misunderstandings surrounding the meaning of tree of life
illustrations, about the "direction" of evolution or the linear development of lineages - both
relevant to the present module - are also of great importance, because it turned out that
tree thinking, interpreting phylogenetic trees, is basically an acquired ability and needs a
similar training as reading skills. This has a particular importance because many textbooks
indirectly, via their use of illustrations, promote some kind of a developmental thinking
about phylogenetics. (see: Sandvik 2008, or Gregory 2008) Misinterpretations of these
illustrations can also be detrimental to one's understanding of the patterns and mechanisms
in evolutionary processes. The module attempts to solve the problem by a game designed to
highlight the important and meaningful features of phylogenetic trees.
5. Historical and philosophical background including nature of science
The general textbook-convention in science courses – if at all focusing on NOS – generally
introduces science as characterizable by a distinct and universal method, with reliance on
empirical data and logical reasoning. This module emphasizes the continuity of scientific
thinking with everyday thinking, and also the overlaps, the connections and the differences
between different fields with respect to reasoning patterns.
The contextualized, historically embedded presentation of the topic highlights that
scientific knowledge plays a significant role in our social and everyday life, and that science
develops through debates and the results - the end products of theory choice situations seem to be self-evident only retrospectively. As opposed to traditional curricula, this
approach is closer to how historians and philosophers of science think about science today.
The historical starting point helps students understand that holding a view which might
seem wrong today - considering the knowledge of the investigated period - was not
necessarily irrational some decades or hundred years earlier.
Below the logical skeleton of the considerations aimed to be clarified by the module is
provided (to gain a deeper understanding of the historical change of the explanations and
theories see: Depew & Weber 1995, Ruse 2008, on the conceptual structure of modern
evolutionary theory see: Sober 1999):
• Explanandum 1 (fact): the diversity of life forms on Earth and their adaptedness to
their environment. (Consensual at the beginning of the 19th century.)
– Explained by different theories of evolutionary mechanisms (e.g. Darwin,
Lamarck) and by reference to geological facts (there are also logically possible
creationist alternatives)
• Explanandum 2 (fact): the historical change of life forms and their distribution in
space and time (This was established as a fact on ground of fossil evidences and
actual observation of change in nature and as a result of artificial selection. Gradually
became consensual in the first half of the 19th century.)
– Explained by different theories of evolutionary mechanisms (e.g. Darwin) and
by reference to geological events. (there are also logically possible creationist
alternatives, like Cuvier's theory)
•
Explanandum 3 (fact): Differences (3.1) and similarities (3.2) between the body
structure (anatomy, cytology, embryological development, DNA) of organisms from
different groups.
– Explanations for 3.1:
• (in pre-Darwinian terms): Differences can be accounted for in terms of
function (the role the organism has to play in its context, in God's plan,
etc.) or in terms of Lamarckism (as an effect of use and disuse, and of
inheritance of acquired characteristics) or
• (in Darwinian terms): Differences can be accounted for in terms of
adaptations by natural selection. (Became consensual at the end of
the 19th century)
– Explanation for 3.2: Similarities can be accounted for in terms of common
origin (homologous = there is functional explanation for it). There are
different types of possible explanations here:
• (in pre-Darwinian terms) there is an archetype in God's mind from
which he always generates new species (Cuvier' theory) or
• (in Darwinian terms) the common descent of organisms form one or
more starting points (Lamarck, Darwin). (Became consensual around
the middle of the 19th century).
•
Basics on the relations between theories and facts:
– Factual claims are descriptions of the world and have a wide range in
complexity. Some of them are controversial others are not, it depends on how
well established they are (e.g. today Kepler's law is considered as a fact, along
with a basic data on planetary positions, a parallel case is the theory of
common descent (see: Hoffman & Weber 2003))
– If a controversial description of the world becomes well established, there is
enough confirmation for it, scientists start to call it a fact as in the case of
evolutionary change (the phase "fact of evolution" usually means = the fact
that in the Earth's history life forms undergone changes).
– A theory is based on empirical facts. The main goal of a theory is to explain
observational data and facts rather than to describe them.
– Until a theory is not corroborated by empirical tests, we usually call it a
hypothesis.
– In some cases, as in the case of common descent, a claim is a theoretical
claim from one perspective and a factual claim form another. E.g., the
phenomena of homological structures are explained by the theory of
common descent. However, we can also say that the (well-established) fact of
common descent is explained by natural selection, etc.
– Factual claims are theory impregnated. To claim that the limbs of two
different species are homologous in the modern sense of the word, one has
to accept the theory of common descent with modification. For a modern
evolutionist it is a basic fact that there are homologous structures in this
sense, although nobody has ever observed this fact directly. We only see
similarities of structures. However, these observations of similarities can be
incorporated into alternative frameworks as well. The available alternative
theories (Cuvier or contemporary creationists) are interpreting the
observational data form the point of view of different theoretical
frameworks; as a result, in different frameworks the same observations
appear to be evidences for a different theory.
– A widespread and disturbing textbook practice is that the evidences for
evolution are usually presented (if presented at all) in a circular way. In many
Hungarian and Anglo-Saxon textbooks it is claimed, that the theory of
evolution (common descent) is evidenced by the existence of homological
structures in the modern sense. A more productive approach would be to
show, that there are criteria for deciding that among the alternatives which is
the better candidate theory in the light of the existing observations (inference
to the best explanation) and which candidate can be tested empirically. This
might help students to understand the reasons behind the acceptance of one
candidate, not another.
6. Target group, curricular relevance and didactical benefit:
Age range: 16-19 years old, higher years of academic secondary school
Institution: High school
Curricular relevance and didactical benefits:
With respect to NOS, the module teaches the notions of fact, observation, theory, theoryladenness. With respect to the biology curricula, its central goal is to teach the theory of
common descent, evidences for descent with modifications, evidences for the changeability
of species. The notion of fossil and the detailed discussion of different dating techniques,
living fossils and ring species are also included.
As an outcome of the learning process, students will see the structure of evolutionary
theory and its many relations to reality and observation. They will be able to distinguish
between different meanings for the label "evolution". The first meaning is the inference,
based on the fossil record, that populations of species on Earth have changed many times in
the history of Earth. In this perspective, evolution is simply the historical change in the
features of living things. The second meaning - like in the case of "Darwinian evolution" - is
the explanation for the mentioned change in terms of mechanisms (e.g. Lamarckian,
Darwinian, etc.). The module clarifies that the acceptance of change and common descent is
independent of the acceptance of specific types of mechanistic explanations for evolution as
a historical process.
The better understanding of the structure of the theory serves the need for an educated
public and it might have an ethical aspect if we consider that poor understanding of
evolution might result in the poor understanding of ecology that has a greater and greater
importance in our lives.
Comparing historically held and received scientific conceptions (special creation, descent
with modification, etc.) with each other helps to gain more clarity about why some
alternative conceptions are erroneous.
As the module uses guided reinvention, and group work as its methods it has a
participative character which helps to motivate students, develops communicative skills and
better attitude towards collaborative work.
7. Activities, methods and media for learning. Case Study:
Lesson 0:
Student knowledge is surveyed. It helps in choosing the topics that are worth more emphasis
in the classroom. Teaching for conceptual change requires an accurate view of the students'
prior knowledge of the topic.
Pretest questions (10 min):
The questionnaire is anonymous. There is no right or wrong answer. Different persons
may give different answers.
1. In your opinion, what is the meaning of the term species? (max 5 sentences)
2. In your opinion, what is the meaning of the term evolution? (max 5 sentences)
3. In your opinion, what factors are responsible for the change of species? (max 5
sentences)
4. In your opinion, what is explained by the theory of evolution? (max 5 sentences)
Lesson 1: Observations, facts and theories
The main learning goal of all this is to reconsider the outmoded concept of empiricism
implicit in the discussion on evidences for evolution in most textbooks on biology.
The lesson begins with a historical introduction into the biological thinking of the
beginning of the 19th century. The central phenomena in the need of explanation for the
biologists of the age (no matter they are theists like Paley, or naturalists like Lamarck) are
discussed. These are:
 the diversity of life
 the high degree of adaptedness of animals to their environment
The finding of new and new transitional life forms (platypus, lungfish) is discussed in
detail. It might be useful in grasping the imagination of the students to tell the story of the
finding of the first platypus in 1798 and the doubts its pelt and sketch - sent back to England
by Captain John Hunter - generated about its originality among British zoologists. The term
transitional form is explained and the problem of the uniqueness of these kinds of animals is
explained. The importance of expeditions in finding these animals and museums in
exhibiting them is pictured. (10 min)
Next, the discovery of new and new fossil remains of extinct species (e.g. giant ground
sloths and the more famous mastodon remains) at the beginning of the 19th century is
discussed and the later discovery of extinct transitional forms is mentioned. The first
reactions to these findings are providing good grounds for showing the differences in
worldview between early and contemporary scientists. (Jefferson's reaction to fossils of
ancient south-American sloths is a good example. "If this animal has once existed, it is
probable on this general view of the movements of nature that he still exists", see: Grayson
1984). It is clarified that thinking about fossils as extinct species was more problematic at
that time, because the bravest estimates for the age of the Earth counted only with a
hundred thousand years. (10 min)
Questions about ammonite fossils: Suppose you are on a holyday somewhere at the
seashore and you find a stone with an ammonite fossil in it. What would be your first
question about it? Is there anything in the need of explanation here? (5min)
 What is it? Is it the remains of a life form or something else?
 What kind of life form is that?
 Is it a fossil of a still existing life form or is it extinct?
 If it is extinct when did it go extinct?
To introduce some logically possible candidate explanations the following questions
are discussed in detail (5min):
 Is it the only possibility, that it is the fossil remains of an extinct life form?
 If it is the remains of an extinct life form is there a need for explaining this
phenomenon?
 What kinds of explanations are possible to the present knowledge of the students?
The story of the origin of the name "Ammonite" is told. The distinctive coiling of the
ammonite shell suggested to the Greeks a resemblance to the horns of the ram. The ram
was regarded as the sacred symbol of the Egyptian god Jupiter Ammon. The teacher than
supports the students with historical examples of possible explanations like:
1. In India, ammonites found in Nepal and northern India are called Saligrams. They
are considered the direct symbol of Lord Vishnu, as one of Vishnu's incarnations
was stone. Saligrams have markings called 'chakras', resembling the discus held in
one of the six hands of the god Vishnu. The stones are kept in temples,
monasteries and households as natural symbols of Vishnu. Water in which
Saligrams have been bathed is drunk daily (to purify the soul).
2. In medieval Europe, fossilized ammonites were thought to be petrified snakes:
"serpentstones". They were taken to be evidence for the actions of saints such as
St. Patrick or St. Hilda.
3. Cuvier’s catastrophe theory combined with his version of special creation. (on
Cuvier see: Depew & Weber 1995)
4. Darwin’s theory of descent with modification.
It is asked of the students in a frontal discussion of the above list: Can the
identification of a pattern in a stone (observation) be reconciled with all the above listed
theories? (15 min)
The conclusions to be obtained are the following:
 The identification of the stone piece with a hundred million (or some hundred
thousand) years old fossil of an extinct life form cannot be reconciled with 1 or 2.
 Facts are theory-laden
 The identification of fossils as remains of extinct life forms is not dependent on the
theory of evolution in its modern form, but depends on the acceptance of geological
theories or on the presuppositions of dating techniques.
Lesson 2: Evidences for change
The lesson aims to show the most important evidences for evolutionary change and also
that fossil as evidences for evolution in themselves are insufficient.
The students are asked what they know about the age of the Earth. After acquiring a
nearly accurate answer it is asked that: Why would any reasonable person think that Earth is
4.5 billion years old. It is a lot of time, how could anyone find that out, if no one was there?
After gathering some basic ideas on stratigraphy and relative dating techniques from the
students, developments in early 19th century geology motivated by the Industrial Revolution
are clarified through the delineation of the catastrophist-uniformitarianist debate. Lyell's
approach to geology and his estimates on the age of the Earth is discussed in a more
detailed form. It is also mentioned, that Darwin himself became a uniformitarianist after
reading Lyell on the voyage of the Beagle and his first successful scientific project was the
formulation of a knew theory on the formation of coral reefs according to Lyell's principles
(see: Ruse 2008, Depew & Weber 1995). (10min)
The most important sources of fossils are mentioned (like the Burgess Shale, etc.). Some
classical examples of fossils are shown from trilobites to mammals that recently gone
extinct. The significance of the estimated age of fossils is emphasized and the structure of
the fossil record is analyzed. Three important observations are mentioned.
 Fossil organisms are found as members of communities, these resemble modern
ecosystems in that they have widespread geographical distribution, and together they
make up seemingly viable communities.
 In any geographical location, the communities are unique, in the sense that they are
restricted to a small portion of the total layers in the location. Although single species
may occur the same communities never appears in higher or lower layers of that
location.
 If two or more of the identified communities are found at the same geographical
location, they always appear in the same order.
Some modern dating techniques, like radiocarbon dating, and the method of endless tree
are introduced to validate the statements.
Then the students are asked, that in their opinion, what seems to be the best explanation
for these geological phenomena and why? If the answer is some sort of an evolutionary
process, than it is mentioned that these findings are also compatible with Cuvier's special
creation hypothesis, therefore we need further evidence to reject Cuvier or to accept
evolution as a better explanation. However, neither Cuvier nor others can reasonably doubt,
that some kind of a historical change has happened in the form and distribution of the
species which inhabited the planet Earth. (10min)
As the next step, the biogeographical distribution of life forms as something in the need
of explanation is exemplified by the well-known Darwin's finches. It is shown that the
geographical distribution in space, the distance between groups of animals has a correlation
with the degree of genetic and anatomical similarities between them. The hypothesis of
adaptive radiation is introduced.
Then the situation is turned again into a frontally coordinated discussion and the students
are asked to compare the virtues of the adaptive radiation hypothesis with the special
creation hypothesis. The goal of this discussion is to reach the conclusion that both adaptive
radiation and special creation provide an explanation for the phenomenon, but radiation is a
scientifically better candidate theory at least in two senses: one might be able to infer some
specific predictions from the radiation hypothesis, and radiation events might be observed
by a naturalist (as in the case of the radiation of passer domesticus from the Central Park
throughout America) in contrast to acts of creation. (15min)
At the end of the lesson the importance of artificial selection and breeding practices in
the argumentation in Darwin’s Origin for the changeability of species and the possibility of
the extrapolation of these observations to the long term is discussed. The notion of ring
species as evidences for the flexibility of species is also depicted on the example of Ensatina
subspecies (see: Ridley 1996). (10min)
Lesson 3: Inference to the best explanation: common descent
The aim of this lesson is to understand the main argumentative pattern behind common
descent. It is also shown, that this pattern is used in other sciences and in everyday life as
well. This emphasizes the continuity of everyday thinking and scientific thinking and the
many connections between different fields of study.
The significance of taxonomical work, and the role of the Linnaean hierarchy in early
biology is shown and the success and importance of comparative anatomy in the first half of
the 19th century is exemplified on Cuvier's case (see: Depew & Weber 1995). His theory on
the four basic archetypes is discussed briefly. It is mentioned that the specific structure of
idealistic taxonomies was in the need of explanation. (5min)
The following two worksheets are distributed among the students with short instructions
on them. The students have to work in small groups and have to write down their answers.
Comparative anatomy questions (8min):
figure 1.
1. Find structural differences between the limbs! (frog, lizard, bird, human, cat, whale, bat)
1.1. In your opinion, what seems to be the best explanation for the found differences?
2. Find structural similarities between these limbs on the picture! Which counterparts can
be found in all of them, which in most of them? Can you recognize a basic pattern?
2.1. In your opinion, what seems to be the best explanation for the found similarities?
The answers of the groups are gathered in a frontal discussion and the groups are asked
to criticize each other's answers if they have any reflection. At the end the right answers are
clarified (1. the shape of the bones, 1.1. function or adaptation, 2. the basic parts of the
limbs are mostly the same, 2.1. common descent with modification). It is mentioned, that
the reasoning pattern used here in 2. and 2.1, is the same as that used in the case of
biogeographical facts. It is also explained how the presence of rudimentary organs in adult
forms or their temporary presence in embryos is strengthening the above argument.
(Rudiments of hind limbs in snakes, teeth in the upper jaws of whale embryos.)
Embryology questions (8min):
The three developmental stages of the different animals are presented on different
pieces of paper. The students are provided with the information that in the first phase all
embryos have a gill!
figure 2.
1. Order the pictures according to the grade of similarity! Lets begin with the Human
picture! Consider all three phases of development when comparing the pictures!
1.1. In your opinion, what seems to be the best explanation for the similarities?
The answers of the groups are gathered in a frontal discussion and the students are asked
to criticize each others answers if they have any reflection. At the end, the right answers are
clarified (1. as presented on the picture, 1.1. common descent with modification). The
Heackel-Serres law is introduced (ontogeny recapitulates phylogeny) and criticized according
to the present day theory which largely follows Darwin in this matter. (Early embryonic
stages resemble the same embryonic stages of related species, but not the adult stages of
these species.)
Questions on comparative linguistics (5min)
How do we know that the following languages are close relatives in the light of the
below presented information? Why do we think that the hypothesis of common ancestry is
not supported by the fact, that in all of these languages there are nouns and verbs?
french
italian
spanish
1
un
uno
uno
2
deux
due
dos
3
trois
tre
tres
4
quatre
quattro
cuatro
5
cinq
cinque
cinco
figure 3.
Plagiarism is discussed as a further example. How can one be sure, that his or her text
was stolen by somebody? What is required in terms of similarity to convince the jury on a
trial about the guiltiness of the defendant?
In a guided frontal discussion students are asked to formulate the common argument
behind the discussed inferences to common origin. It is clarified that the argument is based
on the general presence of homologies in the pre-Darwinian sense and also that the specific
details of similarities and differences are important only in establishing concrete
phylogenetic relationships between groups. It is also emphasized that those biologist who
are working on actual phylogenis are working in the framework of the theory of common
descent and they accept it as a starting point.
The use of inference to the best explanation in science is discussed in some detail (see:
Sober 1999). Then students are requested to apply this argumentation to the universality of
the DNA and are guided to the conclusion that common ancestry is only supported by this, if
the genetic cod is not a biochemical necessity, but it is arbitrary. (8min)
Successful predictions of the theory of common descent are shown in some historical
cases. Thomas Huxley's prediction about transitional forms between reptiles and birds is
discussed. It is mentioned that in 1861 the Archaeopteryx was found. Other examples are
listed (fossil remains of a species halfway between the camel and the lama in North-America,
etc.). It is also emphasized that the alternative theories, like special creation, have no such
predictions. (5min)
Lesson 4: Tree thinking and its diagrams
This lesson aims to make clear the contents of the theory of common descent. The
student's skills in reading evolutionary, phylogenetic trees are improved. Clarifications are
made on common misunderstandings to avoid progressivist interpretations and other over
interpretations.
A classic tree of life picture with homo sapiens on it is shown for the class (it might be
useful to use a truly classical one, e.g. one of Heackel's from the 19th century). Students are
asked to write down their interpretations of the diagram, the places of different taxa on it
and so on. The answers are gathered in an open discussion. (10min)
In the course of the lesson the teacher refers back to the problematic interpretations and
corrects them as they become relevant.
Different types of phylogenetic trees are shown to the students (a pure tree, where only
phylogenetic relations are represented, a tree also representing time scales and one
enriched with information on the change in species diversity). The students are asked in
what respect are these diagrams are similar, what is the basic information that is
represented on all kind of evolutionary trees. The aim of this controlled discussion is to show
that phylogenetic trees basically are diagrammatic descriptions of biological entities
connected through common descent and nothing more. (5min)
Next, the anatomy of a phylogenetic trees, the notions of root, internal node, branch,
terminal node, sister taxa is clarified. Nodes and roots are identified as points of lineage
splitting and as common ancestors. It is shown that the topology (pattern of branching) of
the tree indicates evolutionary relatedness and it is the only information intended on the
diagram. Because the meaning of the word "relationship" is ambiguous in English it is
important to tell students, that "relationship" in biology is a technical term and its only
meaning is the relative recency of common ancestry. (see: Hanno 2008, Gregory 2008)
(5min)
The basic methods for inferring phylogenetic relationships based on comparative
anatomy, cytology and genetics are discussed briefly. Different phylogenis based on different
methods are shown and interpreted (http://www.tree-thinking.org/ is of good use here). It is
clarified that all particular trees of life are only tentative theories on the relationships
between species and not the true phylogeny. Therefore sometimes different methods are
leading to different trees and their reconciliation is also a scientific achievement. (10min)
Phylogeny game (15min):
A game is used to make clear that the order of taxa (terminal nodes), the length of
braches have no meaning on the basic diagrams and there is no "main" branch on the tree.
The students have to work in small groups. Their task is to draw at least three equivalent
trees in the way the below example shows. The first diagram is the starting diagram. It might
be productive with respect to the didactical purposes of the game to use a base diagram
with real taxa (homo sapiens included) at the terminal nodes instead of letters.
After the game is finished every produced diagrams are shown to the class, and students
are asked to correct mistakes in others diagrams.
8. Obstacles to teaching and learning:
The rationale behind teaching NOS relies on teaching critical thinking to students, and
supposes that as a result they will be able to appreciate and evaluate multiple standpoints
and balance them. This ideal does not necessarily take into account the cognitive
development of students. Some studies suggest that developing a sufficient level of
reflective thinking may only be open to a minority of students. In general, little is known of
how good students can be at understanding and utilizing NOS issues. This is a general
problem for any module targeting these skills, but there is no evidence that this module
would pose greater difficulties for students than other similar modules.
9. Pedagogical skills:
The module is based on historical knowledge about biology, therefore some expertise is
required of the teacher concerning history and philosophy of science. Such expertise is of
good use when moderating discussions. The module requires class-management skills. The
open discussions might be inconvenient for teachers not used to inquiry learning.
10. Research evidence:
An earlier version of this module was tested in the Kürt Foundation High School. The
experiences gathered there are built into this version. One central change is that this version
relies less on groupwork, because it turned out that Hungarian students are not accustomed
to the mentioned methods.
11. Further user professional development:
van Dijk, Esther M. & Reydon, Thomas A. C. (2009): A Conceptual Analysis of Evolutionary
Theory for Teacher Education, Science & Education, Online First, DOI: 10.1007/s11191009-9190-x
Gregory, T. Ryan (2008): Understanding Evolutionary Trees, Evolution: Education and
Outreach, Volume 1, Number 2
Hofmann, James R. & Weber, Bruce (2003): The Fact of Evolution: Implications for Science
Education, Science & Education, 12: 729-760
Jensen, Murray S. & Finley, Fred N. (1997): Teaching Evolution Using a Historically Rich
Curriculum & Paired Problem Solving Instructional Strategy, The American Biology
Teacher, Vol. 59, No. 4, pp. 208-212
Mayr, Ernst (2001): What is evolution?, Basic Books
Sandvik, Hanno (2008): Tree thinking cannot taken for granted: challenges for teaching
phylogenetics, Theory in Bioscience, 127: 45-51
Smith, Mike U. (2009): Current Status of Research in Teaching and Learning Evolution: II.
Pedagogical Issues, Science & Education, Online First, DOI: 10.1007/s11191-009-9216-4
12. Written resources:
Depew, David J. & Weber, Bruce (1995): Darwinism Evolving, The MIT Press
Grayson, Donald K. (1984): Nineteenth-century explanations of Pleistocene extinctions: A
review and analysis, in Quaternary Extinctions: A Prehistoric Revolution, ed. Paul S.
Martin and Richard G. Klein, Arizona University press
Ridley, Mark (1996): Evolution, Blackwell Science
Ruse, Michael (2008): Charles Darwin, Blackwell Publishing
Sober, Elliott (1999): Philosophy of Biology, Oxford University Press, 2nd edition
http://www.tree-thinking.org/
http://evolution.berkeley.edu/
Sources for figures:
Figure 1 - Ridely (1996)
Figure 2 - Mayr (2001)
Figure 3 - Sober (1999)