Patterns of Natural Selection

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Types of natural selection

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Directional, Stabilizing, Disruptive

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Speciation

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When a group within a species separates from other members and develops its own unique characteristics.

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Allopatric Speciation

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Occurs due to geographical isolation.

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Three types of natural selection

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Three types of selection occur naturally: stabilizing, directional, and disruptive.

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Directional selection

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Directional selection favors one extreme trait over others, causing a shift in the population.

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Disruptive selection

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Disruptive selection favors extreme traits/phenotypes at both ends of the spectrum, selecting against the average.

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Effect of disruptive selection on phenotype range

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Disruptive selection increases variation by favoring extreme traits/phenotypes.

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Directional selection example

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An example of directional selection is the increase in size of the beaks of finches (birds) during droughts.

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Disruptive selection example

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An example of disruptive selection is the color variation in peppered moths during industrialization.

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Natural selection

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The process by which organisms better adapted to their environment tend to survive and produce more offspring.