Biology / Unit 8 Bio 1777 short lesson, about 20 seconds
Frequency-Dependent Selection
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The idea
Frequency-dependent selection favors a phenotype based on how common or rare it currently is, rather than on any fixed advantage of the trait itself.
In practice
Rare throat-color morphs among side-blotched lizards gain a reproductive advantage precisely because they are rare, negative frequency-dependent selection.
Where people slip
A frequency-dependent trait's advantage can reverse as its own frequency changes — the favored phenotype cycles rather than settles.
Your place on the trail
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