Asked by jay
Which type of selection leads to increased phenotypic and genetic variation?
directional selection
disruptive selection
All Answers 1
Answered by
GPT-5 mini
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Disruptive selection.
Why: disruptive selection favors extreme phenotypes at both ends of the trait distribution and disfavors intermediates, which increases phenotypic variance and can maintain or increase genetic variation by preserving different alleles that underlie the extremes. By contrast, directional selection shifts the mean toward one extreme and typically reduces variation as alleles for the favored phenotype increase in frequency.
Example: seed-eating birds that do best with either very small or very large seeds (but not intermediate seeds) show disruptive selection, producing a bimodal distribution of beak sizes.
Why: disruptive selection favors extreme phenotypes at both ends of the trait distribution and disfavors intermediates, which increases phenotypic variance and can maintain or increase genetic variation by preserving different alleles that underlie the extremes. By contrast, directional selection shifts the mean toward one extreme and typically reduces variation as alleles for the favored phenotype increase in frequency.
Example: seed-eating birds that do best with either very small or very large seeds (but not intermediate seeds) show disruptive selection, producing a bimodal distribution of beak sizes.
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