Biology 1001A Lecture Notes - Lecture 14: Frequency-Dependent Selection, Heterozygote Advantage, Zygosity
11 Dec 2015
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Identify examples of direction, stabilizing, and disruptive selection: directional shifts traits away from existing phenotypic mean to one favored extreme, is extremely common, ex. predatory fish eat smaller guppies, promotes larger body size in guppies. stabilizing intermediate phenotypes have the greatest fitness, 2 extremes aren"t favored, most common mode of natural selection ex. wasps and galls attack all galls (in literacy), but intermediate sized ones survived. disruptive both extreme phenotypes have higher relative fitness, least common, ex. when food is scarce, birds with longer bills are more able to survive. Identify how inbreeding and nonrandom mating affect allele frequencies, and how they affect genotype frequencies: inbreeding increase homozygous genotypes and decrease heterozygous genotypes, recessive phenotypes are often expressed, do not affect allele frequencies. nonrandom mating no selection for one phenotype over another, but individuals with similar genetically based phenotypes usually mate with each other, creating fewer heterozygous offspring, also do not affect allele frequencies.
