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directional selection
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Diagram illustrating three types of natural selection-stabilizing, directional, and diversifying-showing how each affects the distribution of beetle phenotypes in a population over multiple generations. Shaded areas indicate phenotypes selected against, and arrows show shifts in population traits.
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directional selection

biology
Also known as: dynamic selection
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Diagram illustrating three types of natural selection-stabilizing, directional, and diversifying-showing how each affects the distribution of beetle phenotypes in a population over multiple generations. Shaded areas indicate phenotypes selected against, and arrows show shifts in population traits.
Types of natural selection Three types of natural selection, showing the effects of each on the distribution of phenotypes within a population. The downward arrows point to those phenotypes against which selection acts. Stabilizing selection (left column) acts against phenotypes at both extremes of the distribution, favoring the multiplication of intermediate phenotypes. Directional selection (center column) acts against only one extreme of phenotypes, causing a shift in distribution toward the other extreme. Diversifying selection (right column) acts against intermediate phenotypes, creating a split in distribution toward each extreme.

Directional selection is a mode of natural selection where a single phenotype is favored, causing a shift in the population's phenotypic distribution over time. This occurs when environmental conditions change, favoring individuals with traits at one extreme of the phenotypic range.1

This can happen due to changes in the physical or biological environment, or when organisms colonize new habitats. The appearance of a new favorable allele can also drive directional selection. This process requires genetic variation within the population, which is replenished by mutation.1

Human activities, such as the use of pesticides, have also been significant drivers of directional selection, leading to the evolution of resistance in insects. Over long periods, directional selection can lead to significant changes in morphology and ways of life, as seen in the evolution of the human lineage's cranial capacity or the horse's form.1

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2 Britannica Sources
  1. evolution - Directional selection
  2. heredity - Selection

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