1.2 KiB
Unit 3 (TBD) Natural selection is situational. It requires heritable variation, competition, and selective pressures. ==Selective pressure== are environmental conditions pressuring traits. ==Selective advantage== is a genetic advantage.
Sexual selection is mate selection for a particular phenotype. It may affect fitness. Females choose their mates. Good genes hypothesis: Females choose mates on traits that improve chance of survival. Runaway hypothesis: Females choose on basis of traits that improve male appearance. Sexual dimorphism: Different characteristics between male and females to the point that they appear to be separate species. Intersexual selection: Females choose mates based on appearance/phenotype/behavior. Intrasexual selection: Competition between the same sex of same species to pass on DNA.
Stabilizing selection: The intermediate phenotype is favored.
Directional selection: Favors phenotypes at an extreme of the range, resulting in the curve being shifted towards that extreme.
Disruptive selection: Both extremes are favored at the same time. Can eliminate the intermediate phenotype, resulting in speciation.
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