Download The development of evolutionary theory since Darwin

The period of Darwinism
(1859-1882)
1
The development of evolutionary theory since Darwin – Darwinism
The period of Darwinism (1859-1882)
Exercise 1 (home group, individual work):
Read the following text carefully. Your task is to fill in the missing words and phrases, which
you know from your biology lessons. If you need help, you can...
•
…go back in the text or
•
…read further.
If you have problems understanding the text, write down your questions!
Charles Darwin was an enthusiastic natural scientist.
He tried to write down all his observations of animals
and plants and sought to explain them. After his
expedition on the Beagle (fig. 1), which took five
years, Charles Darwin recognized that there had to be
an explanation other than creation by God for the
diversity of life and for the similarities he observed
between the organisms.
Fig. 1: The research ship: the Beagle.
© CNDP, 2009
In 1837 Darwin wrote down the theory of descent
with___________________________ for the first time in
his notebooks. The name of the theory derives from the
Latin descendere (i.e. to descend) and means that
organisms descended from a common ancestor and
Fig. 2: Darwin collected animals.
© CNDP, 2009
changed. Darwin developed this theory by collecting
fossils and animals. He noticed that he could reproduce
lines of related organisms by arranging them in such a way that there were very few
modifications from one organism to the next.
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Marcus Hammann (corresponding author)
2
The development of evolutionary theory since Darwin – Darwinism
In the same year, Darwin described the theory of
__________________________________________ of all
organisms. Later he also included human beings – to the
horror of many. However, Darwin initially wrote down
this idea only in his notebooks. It was essential for him that
all organisms on earth have a common origin.
Fig. 3: Darwin draws a phylogenetic
tree. © CNDP, 2009
In 1838, Darwin explained the change of the species by means of the theory of
______________________________. He was inspired to do so, when he read a book from
Thomas R. Malthus about human population:
“[F]ifteen months after I had begun my systematic
enquiry, I happened to read for amusement Malthus
on Population, and being well prepared to appreciate
the struggle for existence which everywhere goes on
from long-continued observation of the habits of
animals and plants, it at once struck me that under
these circumstances favorable variations would tend
to be preserved, and unfavorable ones to be destroyed.
The result of this would be the formation of a new
Fig. 4: An example of the struggle for
existence. © CNDP, 2009
species.” (Darwin, 1859)
Moreover, Charles Darwin published an additional theory in his important publication ‘On the
origin of species’ (1859): the theory of ____________________________. It says that the
change of species takes place in small steps (gradually) and not in saltations (leaps). Darwin
deduced gradualism from an old tradition in Natural Philosophy, according to which there are
generally no saltations (leaps) in nature.
However, also other researchers made contributions to the development of evolutionary
theory, especially Henry W. Bates and Ernst Haeckel.
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The development of evolutionary theory since Darwin – Darwinism
In 1862, Henry W. Bates observed in the Amazon
region that edible butterflies imitate the coloration of
poisonous or inedible butterflies, when both species
occur in the same habitat. He termed this phenomenon
____________________. When the appearance of
poisonous butterflies varied geographically, Bates
discovered
the
same
variations
among
edible
butterflies. Mimicry means imitation.
Fig. 5: A drawing from Henry W. Bates.
(in: Linn. Soc. 23:495-566, 1862; Source: www.wikipedia.org)
In
1866,
Ernst
Haeckel
described
the
_____________________________________:
“During its rapid and short development, the
organic individual repeats the most important
modifications its ancestors had to pass through
during
their
slow
and
long-lasting
paleontological development according to the
Fig. 6: Each column shows three embryonic steps of
development of a species. Considering the first line
reveals that the different species are very similar to
each other in the beginning of the embryonic
development.
laws of inheritance and adaptation.”
(Haeckel, 1874; Source: www.wikipedia.org)
Five years later Charles Darwin published a further
theory.
He
developed
the
theory
of
_______________________________________,
with the intention to explain characteristics like the
gorgeous tail of the peacock. At first sight it seems to
be disadvantageous for the peacock, but it is favored
by the peahens. The theory of natural selection was
not a sufficient explanation for this phenomenon.
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Marcus Hammann (corresponding author)
Fig. 7: Darwin assumed that females have
apparently a sense of beauty. © CNDP, 2009
4
The development of evolutionary theory since Darwin – Darwinism
Exercise 2 (expert group, teamwork)
Check your cloze texts and your reading comprehension for correctness. Subsequently answer
the following questions:
a) Which term (that Darwin himself never used) is used for Darwin’s first theory of 1837
as it is known today? You know this term from class.
_____________________________________________________________________
_____________________________________________________________________
b) Why do nonpoisonous butterflies imitate the coloration of poisonous butterflies? Why
was Charles Darwin encouraged by these findings?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
c) Why couldn’t Charles Darwin explain the gorgeous tail of the peacock by natural
selection? Find another explanation for the gorgeous tail of the peacock!
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
d) Give further examples for characteristics that developed by means of sexual selection.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
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The development of evolutionary theory since Darwin – Darwinism
Exercise 3 (expert group, individual work)
Copy the terms you filled into the gaps of the cloze text (everything that is underlined) onto
the ‘milestone-cards’ (see last page of the material). There is one card for each milestone from
the period of Darwinism.
Exercise 4 (home group, teamwork):
Each of you is asked to present the milestones of his/her period to the other team members by
attaching the milestone-cards chronologically to the time bar. The expert for the period of
Darwinism starts. For each milestone-card, the expert explains, which person arrived at which
insight by which means and how the insight changed evolutionary theory. Afterwards, the
next expert follows until the time bar is completed.
Exercise 5 (home group, teamwork):
After completing the time bar, your team creates a concept map with as many connections as
possible.
1.) Choose at least 12 milestones from the time bar (each period should be included).
2.) Write down the term from each milestone on a piece of paper.
3.) Arrange the pieces on a blank sheet so that the milestones which have a close
connection lie close to each other. Consider what kind of relationship exists between
the different milestones.
The following advices my help you:
The relation between two terms can be that …
… one term is an example of the other term (i.e.: mimicry is an
example of natural selection)
… one term is part of the other term in the sense of a whole – part
relationship (i.e.: chromosomes contain genes)
… terms are superordinate or subordinate concepts (i.e. mutation
and selection are evolutionary factors)
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The development of evolutionary theory since Darwin – Darwinism
4.) If you are satisfied with the arrangement of the milestones and the relations between
them, glue the pieces of paper on the blank sheet.
5.) Now draw arrows between the terms.
6.) Describe the relationship above the arrows.
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7
The development of evolutionary theory since Darwin – Darwinism
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The development of evolutionary theory since Darwin – Darwinism
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Marcus Hammann (corresponding author)
The period of Neo-Darwinism
(1883-1907)
1
The development of evolutionary theory since Darwin – Neo-Darwinism
The period of Neo-Darwinism (1883-1907)
Exercise 1 (home group, individual work):
Read the following text carefully. Your task is to fill in the missing words and phrases, which
you know from your biology lessons. If you need help, you can...
•
go back in the text or
•
read further or
•
regard the figures carefully.
If you have problems understanding the text, write down your questions!
The term Neo-Darwinism was coined on the occasion of
the revolutionary findings of the scientist August
Weismann. In 1882, August Weismann declared that
there is no _____________________________________
____________________________________________.
August Weismann conducted a spectacular experiment
(see fig. 1), in order to test his hypothesis. He repeated
the experiment over several generations of mice.
In contrast, Charles Darwin believed in the idea, that
acquired traits can be inherited; an idea that was first
formulated by Jean-Baptiste de Lamarck around 1800.
But how did August Weismann explain the findings of
his experiments? He did further research. In 1885 he
discovered that germ line cells are separated from
somatic cells (body cells) very early in the embryonic
development. Accordingly, he postulated the division
between____________________________________.
Fig. 1: The procedure of Weismann’s
experiment. He repeated this experiment 19
times. The offspring of the subsequent
matings provided the basis for the next
experiment.
But how did Weismann explain variability? He assumed _______________________ during
the sexual reproduction to be the solution. He postulated maternal and paternal genetic
material is combined in the form of particles. Figure 2 shows a drawing by August Weismann.
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The development of evolutionary theory since Darwin – Neo-Darwinism
It illustrates how he imagined the process of inheritance. Today we know that the process of
inheritance is much more complicated. August Weismann had no knowledge of
chromosomes and crossing-over. However, the scientist recognized correctly, that sexual
reproduction is the cause of individual differences, which are the basis for natural selection.
Weismann’s assumption represented another breach with traditional concepts in 1886. In that
time many biologists believed that inheritance works like the coalescence of liquids.
According to this idea, sexual reproduction leads to the uniformity in a species, but not to
variability.
Fig. 2: Original drawing from August Weismann. He supposed that
maternal and paternal parts will be inherited as solid particles.
(Fig. from A. Weismann: ”Essays upon heredity“ Vol. I & II, 1889)
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The development of evolutionary theory since Darwin – Neo-Darwinism
The scientist Hugo de Vries rediscovered Mendel’s laws
around 1900 and popularized them. Thereby he became the
founder
of
genetics.
He
reproduced
the
Mendelian
experiments with the evening primrose (fig. 3) and explained
the appearance of new variants after crossbreeding with the
theory of ______________________. De Vries felt confident
that his discovery of spontaneously occurring modifications in
the genetic material – and not natural selection – explained
the change of species. The next years Charles Darwin’s theory
of natural selection receded into the background, while Hugo
de Vries’ theory was mistaken to be the main mechanism of
Fig. 3: Evening primrose. De
Vries reproduced the Mendelian
experiments with this plant.
(Thomé, 1885; Source: www.wikipedia.org)
evolution. Later it became apparent that mutations cannot
completely account for evolutionary the change in species,
but additional evolutionary mechanisms have to take effect, i.e. natural selection.
In 1896, Henri Becquerel discovered radioactivity. This
discovery enabled Marie and Pierre Curie in 1902 to determine
geological time spans just like using a clock. In 1906 it was
possible for the first time to determine the approximate age of
the earth by radioactive measurements. They calculated that the
earth is _____________________ years old. This finding
surprised many scientists, because most of them estimated the
age of the earth to be at the most a few thousand years, whereas
Charles Darwins assumptions, however, were confirmed. He
would have been very happy about this insight.
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Fig. 4:Our globe.
(© Paul Schubert, earthe_01, CC-Lizenz (BY 2.0)
http://creativecommons.org/licenses/by/2.0/de/deed.de;
Source: www.piqs.de )
4
The development of evolutionary theory since Darwin – Neo-Darwinism
Exercise 2 (expert group, teamwork)
Check your cloze texts and your reading comprehension for correctness. Subsequently answer
the following questions:
a) Describe the process of August Weismann’s experiment with mice. What was the
finding of his experiment?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
b) How does August Weismann explain this result?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
c) What causes variability according to the hypothesis August Weismann’ formed in
1886? What fact was he not aware of in this time? Discuss the misconceptions of
Weismann and explain his misunderstandings about the mechanism of inheritance.
Think of meiosis!
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
d) Why was Hugo de Vries mistaken when he supposed that mutations are solely
responsible for the development of new species?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
e) Why would Charles Darwin – if he would have been alive at that time – have been
very happy about the discovery in 1906? (If you cannot find the solution yet, ask the
expert of Darwinism later in the home group.)
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
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Marcus Hammann (corresponding author)
5
The development of evolutionary theory since Darwin – Neo-Darwinism
Exercise 3 (expert group, individual work)
Copy the terms you filled into the gaps of the cloze text (everything that is underlined) onto
the ‘milestone-cards’ (see last page of the material). There is one card for each milestone from
the period of Neo-Darwinism.
Exercise 4 (home group, teamwork):
Each of you is asked to present the milestones of his/her period to the other team members by
attaching the milestone-cards chronologically to the time bar. The expert for the period of
Darwinism starts. For each milestone-card, the expert explains, which person arrived at which
insight by which means and how the insight changed evolutionary theory. Afterwards, the
next expert follows until the time bar is completed.
Exercise 5 (home group, teamwork):
After completing the time bar, your team creates a concept map with as many connections as
possible.
1.) Choose at least 12 milestones from the time bar (each period should be included).
2.) Write down the term from each milestone on a piece of paper.
3.) Arrange the pieces on a blank sheet so that the milestones which have a close
connection lie close to each other. Consider what kind of relationship exists between
the different milestones.
The following advices my help you:
The relation between two terms can be that …
… one term is an example of the other term (i.e.: mimicry is an
example of natural selection).
… one term is part of the other term in the sense of a whole – part
relationship (i.e.: chromosomes contain genes).
… terms are superordinate or subordinate concepts (i.e. mutation
and selection are evolutionary factors).
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Marcus Hammann (corresponding author)
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The development of evolutionary theory since Darwin – Neo-Darwinism
4.) If you are satisfied with the arrangement of the milestones and the relations between
them, glue the pieces of paper on the blank sheet.
5.) Now draw arrows between the terms.
6.) Describe the relationship above the arrows.
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Marcus Hammann (corresponding author)
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The development of evolutionary theory since Darwin – Neo-Darwinism
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Marcus Hammann (corresponding author)
The period of NeoDarwinism and Population
Genetics
(1908-1930)
1
The development of evolutionary theory since Darwin – Population Genetics
The period of Neo-Darwinism and Population Genetics
(1908-1930)
Exercise 1 (home group, individual work):
Read the following text carefully. Your task is to fill in the missing words and phrases, which
you know from your biology lessons. If you need help, you can...
•
…go back in the text or
•
…read further.
If you have problems understanding the text, write down your questions!
In the early 20th century, the integration of Mendelism and Darwinism started. The
rediscovery of Mendel’s laws around 1900 displaced the theory of natural selection by
Charles Darwin. In 1908, Godfrey H. Hardy and Wilhelm R. Weinberg established the
basis for this important integration of theories independent of each other.
In 1908, Hardy attended a conference, at which the frequency of recessive characters was
discussed. The scientist Yule stated that recessive factors (today better known as alleles) will
disappear in the course of a few generations even if natural selection is absent because
dominant factors (alleles) will establish themselves at any rate. Hardy disagreed with Yule’s
statement, but he was not able to disprove it. He was quite unhappy about this. In the same
year, he managed to develop a mathematical formula (see fig. 1). It says that allele
frequencies in “ideal populations”, which means in the absence of factors like selection or
mutation, will remain constant by means of random recombination (see example in fig. 1).
This principle was later called the ______________________________distribution.
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The development of evolutionary theory since Darwin – Population Genetics
p²
frequency of
genotype BB
+
2pq
+
frequency of
genotypes Bb and bB
q²
=
frequency of
genotype bb
Fig. 1: Example of use for the formula of Hardy and Weinberg.
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1
3
The development of evolutionary theory since Darwin – Population Genetics
Two years later, Thomas H. Morgan and his team studied the
inheritance of white eyes in Drosophila (fig. 2). The team discovered
that ________________________ are responsible for the inheritance.
But soon a problem occurred: there were more character states than
chromosomes. Thomas H. Morgan did further research and succeeded in
solving
the
problem.
The
solution
consisted
in
____________________________. Thomas Morgan had to define
them exactly because until then they were simply known as “units of
heredity”.
Fig. 2: Drosophila with red
eyes.
(© André Karwath, CC-Lizenz (BY 2.0)
http://creativecommons.org/licenses/by/2.0/de
/deed.de; Source: www.wikipedia.de )
In 1928, the scientist Frederick Griffith investigated the bacterium Streptococcus
pneumoniae, which causes pneumonia in mammals. He worked with two different strains.
The so-called S-strain (S means smooth) of the bacterium Streptococcus pneumoniae is
characterized by a mucic capsule, which surrounds two connected cells. The other so-called
R-strain (R means rough) has no mucic capsule. Griffith was surprised that he was able to
obtain living pathogenic cells from the dead mice in experiment 4. The mice had obtained a
mixture of pathogenic cells killed by using heat and living harmless cells (fig. 3). Griffith
concluded that some chemical substance from the pathogenic cells had changed (transformed)
the harmless cells. Thus, Griffith discovered the phenomenon of _______________________.
Fig. 3: Frederick Griffith’s experiment. He drew his conclusions from experiment 4.
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The development of evolutionary theory since Darwin – Population Genetics
Sixteen years later, in the year 1944, Oswald T. Avery continued the experiment from
Griffith. Avery succeeded in identifying the mysterious chemical substance, which
transformed the harmless cells into pathogenic cells in the 4th experiment. He discovered the
mysterious molecule responsible for inheritance: ___________. He made this discovery by
relating his experiments to already existing findings of Frederick Griffith.
Fig. 4: The experiment from Oswald T. Avery. He related his experiments to
the findings of Frederick Griffith from the year 1928.
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Marcus Hammann (corresponding author)
5
The development of evolutionary theory since Darwin – Population Genetics
Exercise 2 (expert group, teamwork)
Check your cloze texts and your reading comprehension for correctness. Subsequently answer
the following questions:
a) Imagine you are Godfrey Hardy and would like to persuade scientists like Yule that
recessive and dominant alleles alone do not trigger evolution. Interpret figure 1 in
order to support your argumentation.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
b) How did Thomas H. Morgan solve the problem that there are more character states
than chromosomes?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
c) Describe Frederick Griffith’s experiments. What happened in experiment 4 (fig. 3) so
that the R-cells killed the mice?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
d) Using figure 4, explain, how Oswald T. Avery discovered the mysterious molecule of
inheritance.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
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Marcus Hammann (corresponding author)
6
The development of evolutionary theory since Darwin – Population Genetics
Exercise 3 (expert group, individual work)
Copy the terms you filled into the gaps of the cloze text (everything that is underlined) onto
the ‘milestone-cards’ (see last page of the material). There is one card for each milestone from
the period of population genetics.
Exercise 4 (home group, teamwork):
Each of you is asked to present the milestones of his/her period to the other team members by
attaching the milestone-cards chronologically to the time bar. The expert for the period of
Darwinism starts. For each milestone-card the expert explains, which person arrived at which
insight by which means and how the insight changed evolutionary theory. Afterwards, the
next expert follows until the time bar is completed.
Exercise 5 (home group, teamwork):
After completing the time bar, your team creates a concept map with as many connections as
possible.
1.) Choose at least 12 milestones from the time bar (each period should be included).
2.) Write down the term from each milestone on a piece of paper.
3.) Arrange the pieces on a blank sheet so that the milestones which have a close
connection lie close to each other. Consider what kind of relationship exists between
the different milestones.
The following advices my help you:
The relation between two terms can be that …
… one term is an example of the other term (i.e.: mimicry is an
example of natural selection).
… one term is part of the other term in the sense of a whole – part
relationship (i.e.: chromosomes contain genes).
… terms are superordinate or subordinate concepts (i.e. mutation
and selection are evolutionary factors).
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Marcus Hammann (corresponding author)
7
The development of evolutionary theory since Darwin – Population Genetics
4.) If you are satisfied with the arrangement of the milestones and the relations between
them, glue the pieces of paper on the blank sheet.
5.) Now draw arrows between the terms.
6.) Describe the relationship above the arrows.
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The development of evolutionary theory since Darwin – Population Genetics
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The period of Evolutionary
Synthesis
(1930-1950)
1
The development of evolutionary theory since Darwin – Evolutionary Synthesis
The period of Evolutionary Synthesis (1930-1950)
Exercise 1 (home group, individual work):
Read the following text carefully. Your task is to fill in the missing words and phrases, which
you know from your biology lessons. If you need help, you can...
•
…go back in the text or
•
…read further or
•
…regard the figures carefully.
If you have problems understanding the text, write down your questions!
Six prominent scientists, Theodosius G. Dobzhansky, Ernst Mayr, George Simpson,
Julian S. Huxley, Bernhard Rensch and George L. Stebbins, have been particularly
involved in further developing evolutionary theory. Their findings have been united in the
period of evolutionary synthesis (Synthesis = combination).
In the beginning of this time period, Ronald A. Fisher focused on sexual selection. Whereas
Charles Darwin was able to observe sexual selection only,
Fisher was now able to explain this evolutionary factor. He
revealed that both the female trait ’preference‘ and the male
trait ’ornament‘, i.e. the peacock’s tail, are coded genetically.
Based
on
this
assumption,
he
proposed
the
_________________-process. This hypothesis describes that
male ornaments become bigger and/or more conspicuous by
an automatism.
Fig. 1: The fan-out of a peacock.
(© Josi, Pfau, CC-Lizenz (BY 2.0)
http://creativecommons.org/licenses/by/2.0/de/deed.de;
Source: www.piqs.de )
The genes for the female trait ‘preference’ and the genes for the male trait ‘ornament’ are
genetically associated, because females with a ‘preference’ for conspicuous ornaments mate
with appropriate males and therefore the offspring bears both traits. Furthermore, he
explained that once a male trait becomes too big and/or conspicuous, it will be restrained by
other selection processes (i.e. increased conspicuousness for predators, increased
susceptibility to disease). Fishers’ hypothesis on the runaway-process is able to account for
the evolution of ornaments which are bigger and/or more conspicuous than required in the
attempt to survive.
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The development of evolutionary theory since Darwin – Evolutionary Synthesis
Another important component of evolutionary biology was Ernst Mayrs’ definition of the
biological__________________________ in 1942. Ernst Mayr was not the first scientist who
dealt with this issue. However, in contrast to the morphological species concept, he
emphasized the common gene pool (total number of all genes in a population) and the
reproductive isolation of a species (fig. 2).
Charles Darwin, the prime father of the evolutionary theory, used the term species but never
defined it.
Fig. 2: Very similar but still different: Willow Warbler (left; © Jörg Kretzschmar, 2009) and Chiffchaff (right; ©‫א‬,
)
2008, CC-Lizenz (BY 2.5) http://creativecommons.org/licenses/by/2.5/de/deed.de; Source: www.wikipedia.de
In 1947, Bernhard Rensch studied the origin of new species (speciation). He differentiated
two processes (fig. 3): the evolutionary change of various characteristics in each descendant
(____________________) und the branching of a lineage into two or more descendant lines
(____________________). Rensch came to this conclusion due to the discovery of fossils,
which document these two processes of evolution. Furthermore the scientist explained the
branching of two species by the mechanism of geographical isolation. This evolutionary
mechanism cannot be attributed to
mutation,
recombination
and
selection and was first described by
Ernst Mayr. Charles Darwin also
considered geographical isolation to
be a mechanism of speciation, but
rejected
this
idea
later.
Today,
additional mechanisms of speciation
have been described by researchers.
Fig. 3: Processes of anagenesis and cladogenesis.
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The development of evolutionary theory since Darwin – Evolutionary Synthesis
The mechanism of ____________________________ was first described by Sewall Wright
in 1931 and was integrated into evolutionary theory in 1950. Wright’s discovery is also
named Sewall-Wright-effect and characterizes the random fluctuation in the frequency of
alleles. Therefore, the Sewall-Wright-effect is an evolutionary factor, which is independent of
natural selection. The process described by Wright is especially important for small
populations, where random changes in the frequency of alleles have serious influence.
In the middle of the 20th century the contributions of the aforementioned scientists were
integrated in _____________________________. This great theory combines classical
Darwinism and modern findings of genetics, population genetics and systematics. Genetic
drift, moreover, was identified as an additional evolutionary factor.
According to evolutionary synthesis, mutation and recombination constantly cause genetic
variations, whereas selection and genetic drift constrain these. The geneticist Theodosius
Dobzhansky declared in these days: “Nothing in biology makes sense except in the light of
evolution.”
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The development of evolutionary theory since Darwin – Evolutionary Synthesis
Exercise 2 (expert group, teamwork)
Check your cloze texts and your reading comprehension for correctness. Subsequently answer
the following questions:
a) Ronald A. Fisher explained that a male ornament trait, which becomes too
“expensive”, will be constrained by other selection processes. Which costs has a
peacock to bear in his natural environment due to his ornate train?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
b) Do organisms, which look externally similar, necessarily belong to the same species,
according to Ernst Mayr’s biological species concept?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
c) Why is the evolutionary factor discovered by Sewall Wright independent of natural
selection?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
d) Explain the citation of Theodosius Dobzhansky using the example of sexual
dimorphism.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
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The development of evolutionary theory since Darwin – Evolutionary Synthesis
Exercise 3 (expert group, individual work)
Copy the terms you filled into the gaps of the cloze text (everything that is underlined) onto
the ‘milestone-cards’ (see last page of the material). There is one card for each milestone from
the period of the evolutionary synthesis (just the two discoveries from Bernhard Rensch have
to be noted on one card!).
Exercise 4 (home group, teamwork):
Each of you is asked to present the milestones of his/her period to the other team members by
attaching the milestone-cards chronologically to the time bar. The expert for the period of
Darwinism starts. For each milestone-card, the expert explains, which person arrived at which
insight by which means and how the insight changed evolutionary theory. Afterwards, the
next expert follows until the time bar is completed.
Exercise 5 (home group, teamwork):
After completing the time bar, your team creates a concept map with as many connections as
possible.
1.) Choose at least 12 milestones from the time bar (each period should be included).
2.) Write down the term from each milestone on a piece of paper.
3.) Arrange the pieces on a blank sheet so that the milestones which have a close
connection lie close to each other. Consider what kind of relationship exists between
the different milestones.
The following advices my help you:
The relation between two terms can be that …
… one term is an example of the other term (i.e.: mimicry is an
example of natural selection).
… one term is part of the other term in the sense of a whole – part
relationship (i.e.: chromosomes contain genes).
… terms are superordinate or subordinate concepts (i.e. mutation
and selection are evolutionary factors).
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6
The development of evolutionary theory since Darwin – Evolutionary Synthesis
4.) If you are satisfied with the arrangement of the milestones and the relations between
them, glue the pieces of paper on the blank sheet.
5.) Now draw arrows between the terms.
6.) Describe the relationship above the arrows.
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7
The development of evolutionary theory since Darwin – Evolutionary Synthesis
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Marcus Hammann (corresponding author)
The period of the Enhanced
Evolutionary Eynthesis
(from 1950) (Part 1)
1
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
The period of the Enhanced Evolutionary Synthesis (from 1950)
(Part 1)
Exercise 1 (home group, individual work):
Read the following text carefully. Your task is to fill in the missing words and phrases, which
you know from your biology lessons. If you need help, you can...
•
go back in the text or
•
read further.
If you have problems understanding the text, write down your questions!
The zoologist and marine biologist Adolf Remane
established
in
1952
the
three
main
_________________________________________. They
are a practical tool for research on phylogenetic
relationships because they enable the researcher to
differentiate between homologous and analogous traits.
Homologies can be used to make inferences about kinship
(fig. 1).
Fig. 1: Homologous structures: Front limbs of salamander, turtle, crocodile,
bird, bat, whale, mole, human (from left to right). (Wilhelm Leche, 1909; www.wikipedia.org)
One year later James Watson and Francis Crick
succeeded in clarifying the structure of DNA. At that
time, the molecular components were already known.
The discovery of the structure of DNA was possible
due to the method of X-ray crystallography. Francis
Crick was already familiar with this technique
because he had investigated protein structures this Fig. 2: X-ray photograph
way.
Fig. 3: Structure of
DNA.
(Courtesy of Apers0n;
Source: www.wikipedia.org)
Crick
introduced
Watson
to
X-ray
of DNA. (Courtesy of the National
Institute of Health; Source: www.wikipedia.org)
crystallography after Watson persuaded him that it is a worthy method for
analysing the structure of DNA. A photograph of crystalline DNA
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2
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
triggered an important insight (fig. 2). The photo was a result of the research of the X-ray
expert Rosalind Franklin, who started her work in 1951 at the same college as Watson and
Crick. From the photo, Watson concluded that the shape of a DNA molecule is a
_________________________ (fig. 3). The researcher had seen X-ray photos of other helical
molecules before. Subsequently, Watson and Crick reconstructed the exact plan of a DNA
molecule with the aid of handmade wire models and finally published the DNA structure in
1953.
Linus Pauling and Emile Zuckerkandl first postulated the
concept of the ________________________________ in 1961.
The discovery displays a measuring tool for estimating
evolutionary distances. The basis for this concept is the
following correlation: The longer two systematic entities are
separated, the bigger is the number of differences in nucleotides
Fig. 4: An illustration of the
discovery from Pauling and
Zuckerkandl.
(Courtesy of Apers0n and Trojan respectively;
Source: www.wikipedia.org)
and changes in amino acids. The molecular clock corresponds
with mutation rates of single genes or with differences between
sequences in single proteins. This technique cannot be applied
in every case, because not all genes or proteins possess a reliable average evolutionary rate.
Therefore this method is hardly ever exact. The clock can be adjusted by the fossil record and
enables the researcher to estimate e.g. at which time a specific speciation event took place.
Even insights from geology played an important role for developing evolutionary theory
further.
In
1962,
geology
was
revolutionized
by
the
theory
of
______________________________. The theory comprised the movement of plate tectonics
and the forces which affect it. Furthermore, the theory explains the distribution of volcanoes,
earthquakes, mountains, rock formations and the structures of the sea floor. The formation of
these large-scale geological structures can be accounted for by the movement of the tectonic
plates. As early as 1915, Alfred Wegener postulated the theory of continental drift based on
his observation that the continents surrounding the Atlantic fit together like a puzzle. His
theory was not accepted at that time because his assumptions on the driving force of plate
tectonics proved wrong. Wegener hypothesized the tidal forces of the moon and the sun to
cause this movement.
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The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
In 1962, Harry Hess and Robert Dietz found a plausible explanation for the driving force of
plate tectonics, which is still accepted today. Hess and Dietz realized that convection (lat.
convehere = to convey) in the mantle of the earth can passively pull and push the continents
(see fig. 5).
Fig. 5: Convection. A comparison. (The numbering belongs to exercise 2c).
Another problem in evolutionary biology was the
explanation of altruistic (unselfish) behavior. Already
in the 19th century Charles Darwin, the father of
evolutionary
theory,
described
leaving
(direct)
offspring as the highest aim in life for each
individual. But he would not have been able to
explain, why Belding’s Ground Squirrels take a high
risk of dying, when they warn other members of their
Fig. 6: A Ground Squirrel watches for
predators.
(© Ute Steinbrecher, Wachposten, CC-Lizenz (BY 2.0)
http://creativecommons.org/licenses/by/2.0/de/deed.de;
Source: www.piqs.de )
species against predators. The animals utter a shrill
warning cry, which does not only inform other
members of their species about danger but also
informs predators about the position of the alerter. Today it is known that the animals only
risk their life when they are surrounded by closely related members of their species. For the
relatives the chance of survival is increased enormously by the warning cry.
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The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
The behavior of Belding’s Ground Squirrel can be explained by the so-called kin selection. In
1964, William Hamilton developed a formula in order to predict under which circumstances
unselfish behavior occurs. The basis for the formula and therefore the cause for altruistic
behavior were already known in 1964: unselfish behavior depends on the degree of
relationship. If the degree of relationship is known, it is possible to decide, if
_______________________________ exists or not, due to the Hamilton-formula. Kin
selection is a kind of natural selection because it increases the likelihood of passing on one’s
genes (contains in the close relatives) to the next generation.
Two
years later, the zoologist Willi Hennig elaborated on the principle of
_______________________________________, he had first described in 1950. This
principle represents an application of Darwin’s theory of common descent to the discipline of
systematics. Willi Hennig defined systematic groups as groups of organisms which share a
common ancestor as well as all descendants of this ancestor. In contrast to this, classical
systematics before Hennig often described groups, which did not comprise all descendants of
a common ancestor (see fig. 7).
Fig. 7: A cladogram.
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Marcus Hammann (corresponding author)
5
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
Exercise 2 (expert group, teamwork)
Check your cloze texts and your reading comprehension for correctness. Subsequently answer
the following questions:
a) Read up on the criteria of homology by Adolf Remane and give one example for each.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
b) Specify the components of a DNA molecule.
_____________________________________________________________________
_____________________________________________________________________
c) Explain the meaning of convection flow. Thereto, cut the pieces of the sentences on
the page 8 and arrange them so that they are in accordance with the numbers in figure
5.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
d) Explain why altruistic behavior is finally selfish.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
e) Explain by means of figure 7, why reptiles do not exist as a systematic group in
phylogenetic systematics.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
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Marcus Hammann (corresponding author)
6
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
Exercise 3 (expert group, individual work)
Copy the terms you filled into the gaps of the cloze text (everything that is underlined) onto
the ‘milestone-cards’ (see last page of the material). There is one card for each milestone from
the period of the enhanced evolutionary synthesis (part 1).
Exercise 4 (home group, teamwork):
Each of you is asked to present the milestones of his/her period to the other team members by
attaching the milestone-cards chronologically to the time bar. The expert for the period of
Darwinism starts. For each milestone-card, the expert explains, which person arrived at which
insight by which means and how the insight changed evolutionary theory. Afterwards, the
next expert follows until the time bar is completed.
Exercise 5 (home group, teamwork):
After completing the time bar, your team creates a concept map with as many connections as
possible.
1.) Choose at least 12 milestones from the time bar (each period should be included).
2.) Write down the term from each milestone on a piece of paper.
3.) Arrange the pieces on a blank sheet so that the milestones which have a close
connection lie close to each other. Consider what kind of relationship exists between
the different milestones.
The following advices my help you:
The relation between two terms can be that …
… one term is an example of the other term (i.e.: mimicry is an
example of natural selection).
… one term is part of the other term in the sense of a whole – part
relationship (i.e.: chromosomes contain genes).
… terms are superordinate or subordinate concepts (i.e. mutation
and selection are evolutionary factors).
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Marcus Hammann (corresponding author)
7
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
4.) If you are satisfied with the arrangement of the milestones and the relations between
them, glue the pieces of paper on the blank sheet.
5.) Now draw arrows between the terms.
6.) Describe the relationship above the arrows.
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Marcus Hammann (corresponding author)
8
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
… heats up
and moves
upward again.
… and submerge in the
mantle of the earth, where
it melts and the hot melted
material moves upward again.
Hot material moves
upward from the
mantel of the earth …
…and leads to the origin and separation
of tectonic plates.
Through convection water
moves from the bottom to
the surface …
… cools down, moves
sideward and sinks
down…
Where tectonic plates
converge the cooler plate
will submerge under the
upper one...
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9
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 1
www.evolution-of-life.com
Marcus Hammann (corresponding author)
The period of the Enhanced
Evolutionary Synthesis
(from 1950) (Part 2)
1
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
The period of the Enhanced Evolutionary Synthesis (from 1950)
(Part 2)
Exercise 1 (home group, individual work):
Read the following text carefully. Your task is to fill in the missing words and phrases, which
you know from your biology lessons. If you need help, you can...
•
…go back in the text or
•
…read further.
If you have problems understanding the text, write down your questions!
In the 1960s, the Japanese scientist Motoo Kimura investigated the degree of genetic
variance in natural populations. He critically looked at the common assumption that
mutations are either disadvantageous or advantageous because it contradicts the possibility of
a great number of variations. Kimura applied a method, which enabled him to investigate the
variance between individuals on the level of proteins. It turned out that the amino acid
sequences of proteins in one population differed more often than previously assumed. Thus,
Kimura concluded that most changes in the DNA do not have any influence on the survival
and the reproduction rate of an organism. In other words, Kimura found out that most
mutations are neutral. In 1968, he published his theory of ___________________evolution.
This discovery did not contradict to the concept of natural selection, but rather added to
existing evolutionary concepts. Not every mutation leads to phenotypical changes, which are
subject to selection.
Although Watson and Crick had analyzed the structure of DNA in the 1950s, it remained
unclear, how this structure encodes information. Theoretical considerations suggested that
three nucleotides contribute the information for one amino acid. Marshall Nirenberg and
Heinrich Matthaei first succeeded in 1961 in synthesizing triplets (consisting of three
nucleotides) outside a cell. They found out that RNA-triplets consisting of Uracil-nucleotides
encode the amino acid phenylalanine. Soon they were able to synthesize RNA-triplets with
nucleotide sequences in any combination.
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The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
The following figures illustrate an experiment for
identifying the amino acid which is encoded by the
triplet UUG. The preparation for the experiment is
shown in figure 1. Then, 20 test-tubes are filled
with defined components, with each test-tube
containing different radioactively labeled amino
acids. The test-tubes are left standing some time,
so that the UUG-triplets can attach to the
corresponding amino acid and to the ribosome.
Afterwards, the main test run starts, composed of a
Fig. 1: Illustration of the preparation. A total
of 20 test-tubes are filled with the defined
components. Each test-tube contains another
radioactive labeled amino acid.
maximum of 20 experiments (see figure 2).
Next, the contents of each test-tube are filtered.
The special filter retains only the ribosome and the
attached components. Then, analyses of all 20 test-tubes reveal, in which test-tube
radioactively labeled amino acid are retained.
Fig. 2: The course of the test runs by Marshall and Nirenberg using the example of the triplet UUG.
Two from a total of 20 experiments are illustrated (see arrow). The content of each test-tube will be
filtered.
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The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
Nearly at the same time the scientist Har Gobind Khorana succeeded in synthesizing longer
RNA-fragments outside the cell. Thus, the three scientists gained further insights into the
nature of the codons. Thus the whole ________________________________ could be
decoded in 1966.
The genetecist Lynn Margulis rediscovered the ________________________________ in
1970. The theory was originally formulated by the Russian Merezhkowsky, who published it
in 1910 without attracting further interest. The theory of endosymbiosis explains that
chloroplasts and mitochondria of the eukaryotes are descendants from freely living
prokaryotes, which entered the host cells through endosymbiosis at some point in the course
of evolution.
Fig. 3: The theory of endosymbiosis.
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The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
In
1977,
Frederick
Sanger
developed
the
method
of
__________________________________. This method enabled researchers to determine the
nucleotide sequence of a DNA molecule. The result is the sequence of the DNA strand which
is complementary to the template.
The basis of this method is the random assembly of a modified nucleotide (ddATP, ddCTP,
ddTTP or ddGTP) during DNA-replication. It provokes the termination of the synthesis of the
amplified strand, because the 3’-OH-end for the attachment of the next nucleotide is lacking.
This results in many DNA fragments of different length, which can be separated by size
through gel electrophoresis. Radioactive bands can be made visible (fig. 4) through
autoradiography.
Fig. 4: The method of DNA sequencing according to Frederick Sanger.
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5
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
Another important step in the further development of evolutionary theory was the integration
of the developmental biology, which deals with the development from the zygote to the
complete organism. In 1980, the scientists Edward Lewis, Eric Wieschaus and Christiane
Nüsslein-Volhard discovered the so called homeotic genes, which control embryonic
development. These genes determine where, when and how specific segments of the body,
like e.g. eyes or extremities, develop in an organism. Edward Lewis found the first of these
genes when he investigated a Drosophila mutant bearing two instead of one pair of wings
(fig. 5). Meanwhile, ________________________________ have been found in many
different species. It became clear that particular nucleotide sequences (so-called
‘homeoboxes’) of these genes are identical or very similar in many species.
A
B
Fig. 5:
A Drosophila wild type
B Drosophila mutant,
bearing two instead of
one pair of wings.
© Markus Tögel, Werner Mangerich,
Prof. Dr. Achim Paululat (University of
Osnabrück), 2010
In 1982, John Maynard Smith made another important contribution. He applied the game
theory, commonly used in economics, in order to explain behavioral patterns from an
evolutionary perspective. Often, it can be observed that individuals of a species use different
behavioral strategies in identical contexts. The game theory allows for predicting, when
alternative behavioral strategies can exist in parallel and when one strategy displaces the
other. Strategies, which stand up to alternative behavioral strategies and resist change, are
called ________________________________ (ESS). By means of applying game theory and
identifying evolutionary stable strategies it was possible to explain behavioral strategies,
which had hitherto been unable to explain from the perspective of individual selection alone.
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The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
Exercise 2 (expert group, teamwork)
Check your cloze texts and your reading comprehension for correctness. Subsequently answer
the following questions:
a) Because of the nature of the genetic code some point mutations do not result in a
different gene product. Use the codon table to find out, at which positions of a
nucleotide triplet neutral mutations can occur! Give an example.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
b) Which amino acid is encoded by the triplet UUG? How did Nirenberg and Matthaei
discover this? Explain how the experiment was conducted with the aid of the text and
the figures.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
c) Use figure 3 to explain, how the theory of endsymbiosis explains the formation of
cells with mitochondria and chloroplasts.
_____________________________________________________________________
_____________________________________________________________________
____________________________________________________________________
_____________________________________________________________________
d) Use the example of the fly with two pairs of wings in order to explain the function of
homeotic genes.
_____________________________________________________________________
_____________________________________________________________________
____________________________________________________________________
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Marcus Hammann (corresponding author)
7
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
Exercise 3 (expert group, individual work)
Copy the terms you filled into the gaps of the cloze text (everything that is underlined) onto
the ‘milestone-cards’ (see last page of the material). There is one card for each milestone from
the period of the enhanced evolutionary synthesis (part 2).
Exercise 4 (home group, teamwork):
Each of you is asked to present the milestones of his/her period to the other team members by
attaching the milestone-cards chronologically to the time bar. The expert for the period of
Darwinism starts. For each milestone-card, the expert explains, which person arrived at which
insight by which means and how the insight changed evolutionary theory. Afterwards, the
next expert follows until the time bar is completed.
Exercise 5 (home group, teamwork):
After completing the time bar, your team creates a concept map with as many connections as
possible.
1.) Choose at least 12 milestones from the time bar (each period should be included).
2.) Write down the term from each milestone on a piece of paper.
3.) Arrange the pieces on a blank sheet so that the milestones which have a close
connection lie close to each other. Consider what kind of relationship exists between
the different milestones.
The following advices my help you:
The relation between two terms can be that …
… one term is an example of the other term (i.e.: mimicry is an
example of natural selection).
… one term is part of the other term in the sense of a whole – part
relationship (i.e.: chromosomes contain genes).
… terms are superordinate or subordinate concepts (i.e. mutation
and selection are evolutionary factors).
www.evolution-of-life.com
Marcus Hammann (corresponding author)
8
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
4.) If you are satisfied with the arrangement of the milestones and the relations between
them, glue the pieces of paper on the blank sheet.
5.) Now draw arrows between the terms.
6.) Describe the relationship above the arrows.
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Marcus Hammann (corresponding author)
9
The developm ent of evol utionary theory since Da rwin – Enhanced Evoluti onary Synthesis 2
www.evolution-of-life.com
Marcus Hammann (corresponding author)