Directional selection is a type of natural selection where one extreme phenotype is favored over others. This leads to a shift in the population's trait distribution toward that extreme.
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The average phenotype in the population changes over time.
Directional selection can lead to rapid evolutionary changes.
It often occurs when environmental conditions change or when a population colonizes a new habitat.
An example of directional selection is the increase in beak size among finches in response to food availability.
It reduces genetic diversity by favoring one extreme phenotype.
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Related terms
Stabilizing Selection: Natural selection that favors intermediate variants and acts against extreme phenotypes.
Disruptive Selection: Natural selection that simultaneously favors individuals at both extremes of the phenotypic range.
Adaptive Evolution: The process through which populations become better suited to their environment due to natural selection.