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Evolution
Theory of Natural Selection
• Conceived of by
Charles Darwin
• Published in 1859
• Resulted from
Darwin’s observations
on his trip around the
world from 1831-1836
• Took Darwin over 20
years to finalize
Theory of Natural Selection
• Artificial selection is
used by man to select
for desired traits in
animals and plants.
• Natural Selection is
the process by which
nature selects the
most well adapted
organisms to move on
through reproduction
Theory of Natural Selection
• Variation
– Individuals in a
population differ from
one another
Theory of Natural Selection
• Heritability
– Variations are
inherited from parents.
Tall organisms
produce tall organisms
and short produce
short.
– DNA is the mechanism
for transfer
Theory of Natural Selection
• Overproduction
– Populations produce
more offspring than
can survive.
– Due to variation each
is slightly different than
the next.
Theory of Natural Selection
• Reproductive
Advantage
– Some variations prove
to be advantageous in
the environment and
are passed on to
offspring who have a
competitive advantage
thanks to these
variations.
Theory of Natural Selection
• Evolution is the end
result of cumulative
changes in groups of
organisms over time.
Adaptation
• An adaptation is a
trait shaped by
natural selection
that increases an
organism’s
reproductive
success.
• Measures by the
“fitness” of an
organism
Types of Adaptation
• Camouflage is an
adaptation that
allows an organism
to blend in to their
environment.
• Mimicry is an
adaptation in which
one species evolves
to resemble another
species.
Mechanisms of Evolution
• Population Genetics
– Hardy-Weinberg Principle is about the
concept of Genetic Equilibrium.
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Large population
No Immigration and emigration
Random mating
No mutations
No natural selection
– Immpossible!!
Mechanisms of Evolution
• Genetic Drift
– Any change in allele
frequency in a
population due to
chance.
Mechanisms of Evolution
• Gene Flow
– The random
movement of
individuals between
populations or
migration increases
genetic variation in the
population.
Mechanisms of Evolution
• Nonrandom Mating
– Mating is not random.
Mechanisms of Evolution
• Mutation
– A random change in
genetic material that
results in changes in
the phenotype of an
organism.
Mechanisms of Evolution
• Natural Selection
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Stabilizing selection
Directional selection
Disruptive selection
Sexual selection
Mechanisms of Evolution
• Reproductive
Isolation
– Organisms are
physically or
temporally isolated
and as a result the are
not able to mate and
exchange genetic
material.
Mechanisms of Evolution
• Speciation
– Allopatric speciation
• Species evolve due to
being divided by a
physical barrier
– Sympatric speciation
• Species evolve without
a physical barrier
Patterns of Evolution
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Adaptive Radiation
Coevolution
Convergent Evolution
Rate of Speciation
– Gradualism
– Punctuated Equlibrium