7.6 Speciation
Notes
Speciation is the formation of new species. A species is a group of organisms that can breed and produce fertile offspring.
- Speciation requires reproductive isolation: populations stop interbreeding.
- Geographic isolation: a physical barrier (river, mountain, ocean) separates populations. They evolve separately.
- Behavioral isolation: different courtship songs or dances. Temporal isolation: breeding at different times.
- Adaptive radiation: one ancestor gives rise to many species filling different niches (Darwin's finches).
- Gradualism is slow, steady change; punctuated equilibrium is long stable periods broken by rapid change.
Practice
A horse and a donkey can mate and produce a mule, but mules are sterile. Are horses and donkeys the same species?
A species must produce fertile offspring.
Two populations of squirrels are separated by the Grand Canyon and slowly become different species. This is caused by:
A physical barrier stopped the populations from interbreeding.
Two frog species live in the same pond, but one breeds in early spring and the other in late spring. This is:
Breeding at different times keeps their gene pools separate.
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