Directional selection

Definition

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.

5 Must Know Facts For Your Next Test

1. The average phenotype in the population changes over time.
2. Directional selection can lead to rapid evolutionary changes.
3. It often occurs when environmental conditions change or when a population colonizes a new habitat.
4. An example of directional selection is the increase in beak size among finches in response to food availability.
5. It reduces genetic diversity by favoring one extreme phenotype.

Review Questions

• What happens to the average phenotype in a population experiencing directional selection?
• Can directional selection lead to rapid evolutionary changes? Explain how.
• Provide an example of directional selection and describe its impact on the population.

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.