Download Evidence of evolution

The Theory of Evolution
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Charles Darwin
Evidence for evolution
Mechanisms for evolution
Natural selection
Speciation
Evidence of evolution
• Structural adaptations
– Mimicry
– Camouflage
• Physiological adaptations
– Change in a metabolic process
• Fossils
• Anatomy
– Homologous structures
– Analogous structures
– Vestigial structure
– Embryos
• Biochemistry
http://evolution.berkeley.edu/evolibrary/home.php
Theory of Natural Selection
The Theory of Evolution
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• Observation:
Charles Darwin
Evidence for evolution
Mechanisms for evolution
Natural selection
Speciation
Limits are placed on population expansion by
limited environmental resources
• Conclusion:
Therefore not all organisms will survive to
adulthood and reproduce
– therefore there must be a “struggle for existence”
(Source: observations reinforced by Malthus)
http://evolution.berkeley.edu/evolibrary/home.php
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Theory of Natural Selection
Theory of Natural Selection
Conclusions:
Observations:
• Not all members of a species are alike
(variation)
• Parents often pass their individual
variations on to their offspring
• individuals featuring favorable
variations will enjoy a competitive
advantage over others
• they will survive in proportionately
greater numbers and will produce
offspring in increasingly greater
numbers
(Source: Animal breeders, taxonomists)
Theory of Natural Selection
There is “differential reproduction”
and “differential survival,” i.e.,
“natural selection”
(Author of inference: Darwin)
Theory of Natural Selection
Conclusion:
• Through the action of
natural selection over many
generations a species could
evolve
(Author of inference: Darwin)
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Theory of Natural Selection
Both Darwin and Wallace knew:
the principle cause of
natural selection
is the environment
Biston betularia
Theory of Natural Selection
(a) The dark form is more
visible on the light, lichencovered tree.
(b) On trees darkened by
pollution, the lighter form is
more visible.
Variation in the peppered moth.
Understanding Physical Anthropology and Archaeology, 9th ed., p. 29
But look at them without color vision.
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Theory of Natural Selection
• The moths satisfy all four conditions for natural
selection:
• they reproduce;
• their color pattern is inherited;
• there is variation in their color patterns;
• the different forms have different fitness.
Mechanisms for evolution
• Do populations or individuals evolve? Populations
• What is a gene pool? All of the alleles in a population
• How can the gene pool change?
– Mutation
– Genetic drift
– Gene flow
• Would these things effect a large population or a
small population more?
Contrasting ideas about the mechanism of evolution.
(a)According to Lamarck’s theory
(b) According to the Darwin-Wallace
Understanding Physical Anthropology and Archaeology, 9th ed., p. 24
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The Theory of Evolution
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Charles Darwin
Evidence for evolution
Mechanisms for evolution
Natural selection
Speciation
http://evolution.berkeley.edu/evolibrary/home.php
What is speciation?
What is speciation?
• Geographic isolation
• Reproductive isolation
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Geographic isolation
Reproductive isolation
Gradualism
Punctuated equilibrium
http://evolution.berkeley.edu/evolibrary/home.php
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What is speciation?
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Geographic isolation
Reproductive isolation
Gradualism
Punctuated equilibrium
Divergent evolution
Adaptive radiation – an example of
divergent evolution
– Adaptive radiation
• Convergent evolution
http://www.vanderbilt.edu/AnS/english/Clayton/G alapago_finches.gif
http://evolution.berkeley.edu/evolibrary/home.php
Convergent evolution – what is an
example?
Theory of Natural Selection
• Problem
What is the source of
individual variation?
lack of knowledge of
modern genetics
http://evolution.berkeley.edu/evolibrary/home.php
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Theory of Natural Selection
Neither Darwin nor Wallace knew:
the source of
individual variation
=
genetics
(inherited characteristics)
Theory of Natural Selection
Problem:
If natural selection only weeds out
what already exists, how can it
produce anything new?
Didn’t know then because of lack of
knowledge of mutation and sexual
recombination from modern genetics
Mechanisms for evolution
• Do populations or individuals evolve?
• What is a gene pool?
• How can the gene pool change?
– Mutation
– Genetic drift
– Gene flow
• Would these things effect a large population or a small
population more?
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