Theory of Evolution

I DO Guided Notes

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Theory of Evolution: An
explanation of the changes in
animal traits over time.
(Theories change with new
evidence.)

Genetic Variation

➔ In any population, there are a variety of traits

from organism to organism. (Tall/short,
fast/slow, good eyesight/poor eyesight)

➔ This genetic variation allows for certain

individuals to have an advantage in their
specific environment

➔ Individuals with advantages live long enough

to reproduce and pass these traits to their
offspring.

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Natural Selection

⦿ Over time, more individuals that are

best adapted to their environment
make up a population.

› Small changes add up over long periods

of time.

› New species arise from existing ones.

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Survival of the Fittest

⦿ In every population, there will be some individuals

that can run faster, use camouflage, or fight better.

⦿ “Fitness” does not mean the strongest. Instead, it

refers to the organisms that are best suited to their
environment.

⦿ Fitness is measured as the ability to survive and

reproduce in order to pass on the traits that are an
advantage.

Evidence of Evolution: Fossil

Record

⦿ Fossil – the preserved

remains of a dead organisms.

⦿ Fossil Record – the

incomplete record of the
extinct organisms that are
related to each other and
their common ancestor.

› Provides evidence of organisms

that once existed but are now
extinct.

› Similarities between fossils

suggest how one species might
have changed and given rise to
another.
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Adapt or Extinct:

If populations are not adapted to
their environment, they will go
extinct.

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We Do

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