Adaptation and Heredity
• Jean Baptiste Pierre Antoine de Monet, Chevalier
de Lamarck (1744-1849) proposed new ideas
about evolution.
• Lamarck believe that “use and disuse” would
determine how species changed over time.
– Athletic training increases muscle size
– Constant stretching for high branches = giraffe necks
• He also believed that these traits could be passed
on
• But he did propose that species evolve over
time in response to their environment, and
changes are passed on over generations.
• Charles Darwin began tracking observations in
1837, collecting data which he would use to
create his theories on evolution.
• Much of his work is based on biogeography:
the study of geographic distribution of
organisms.
• Remote islands provided him a unique area to
study, finding animals with unique behaviour
and no fear of humans.
Darwin’s Theory of Natural Selection
• Individuals born with an advantage
(adaptation) would have the best chance for
survival and then propagate; therefore
increasing the strength of the species.
• Note:
– Individuals ADAPT, populations EVOLVE.
– A single change does not represent evolution until
it causes a population change.
Example of natural selection
• Darwin’s finches on the Galapagos Islands
– The only feature that changed is the size and
shape of their beaks.
– Occurred due to isolation and chance.
• Natural Selection:
– Works on the
appearance of
phenotypes, not
genotypes that produce
the trait.
– Reduces, but does not
eliminate, the range of
phenotypes.
– Shifts populations
phenotypes based on
environment.
Key Points of Natural Selection
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Individuals within a species vary in many ways.
Some of this variability is inheritable.
Members of the same species compete.
Organisms produce more offspring than the
environment can support, so only some will survive.
• Individuals with favourable variations are more likely to
survive.
• As these individuals contribute proportionately more
offspring to succeeding generations, the favourable
generations will become more common.
Other Supporting Evidence
• Many organisms have homologous features:
– Similar structures evolved with different functions.
• Many organisms have analogous features:
– Structures that perform similar functions but
without the same structures or origins.
• Many organisms show vestigial features:
– Missing or non-functioning structures that are
found in an organism.
• What Affects Evolution??
• Convergent Evolution – two species become
similar due to environmental pressures.
• Divergent Evolution – two or more species
become increasingly different due to
environmental pressures.
• Coevolution – the evolution of one species as
a response to the evolution of another
species.