Natural Selection
Charles Darwin’s Big Ideas!
Principles of Natural Selection
There is variation within populations (i.e.; not
all penguins or dandelions are alike)
Variation is a result of sexual reproduction
and mutations in genes
More offspring are produced than can live
There is competition for limited resources
Organisms with the best traits (adaptations)
survive and pass on their genes to their
offspring
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Polar Bear Paragraph
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Polar Bears, with their thick
layer of fur and fat, are well
adapted to cold climates. In
terms of evolution and natural
selection, how did these
changes in the polar bear occur
over time?
Polar Bear Paragraph Answer
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There is variation among polar bears.
Not all polar bears are the same due to
genetic differences. Some polar bears
are better adapted (just by luck!) to
their environment. More polar bears
are produced than can survive. There
is competition for limited resources.
Those polar bears with the best traits,
survive and pass on their genes for
thick fur and fat to their offspring.
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Cave Salamander Paragraph
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Cave Salamanders are blind
(they have eyes which are not
functional). How would a
biologist explain how blind cave
salamanders evolved from
sighted salamander ancestors?
Cave Salamander Answer
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There is variation among cave salamanders.
Not all cave salamanders are the same due to
genetic differences. Some cave salamanders
are better adapted (just by luck!) to their
environment. More salamanders are
produced than can survive. There is
competition for limited resources. Blind cave
salamanders are able to smell food more
easily. Those cave salamanders with the best
trait(s) survived and passed on the gene for
being blind to their offspring.
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