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Speciation
Chapter 16 –Section 3
Speciation-The Formation of
a New Species
1. Common ancestors arrive in an
environment.
There is diversity in the gene pool
causing a variety of phenotypes.
2. Geographic isolation
Due to competition members of a
population are driven to different
locations.
i.e. The other side of the river,
another island, out of the
forest and into the
desert…
3. Changes in the Gene Pool.
Due to differing environments, the
phenotypes that are naturally
selected for are different for each
environment.
Each population drifts towards it’s own
fittest phenotypes
4. Reproductive isolation
After many generations of Natural
Selection leading the two
populations of organisms towards
different phenotypes, the two
populations are no longer able to
reproduce with each other.
5. Ecological Competition
Even if the two populations
begin to mix in the same
environment again, their
phenotypes are so different that
competition drives them towards
different behaviors and food
sources.
6. Continued Evolution
As the generations pass, the
phenotypes continue to drift
apart, as the behaviors and food
sources are not similar.
• Write a paragraph explaining how
the speciation of the two tortoises
on the Galapagos Islands may
have evolved from the same
ancestor.