Foundations of Bio Lecture 32

four processes driving evolution

natural selection, genetic drift, gene flow, mutation

gene pool

sum of all copies of all alleles at all loci in a population; source of genetic variation producing the phenotypic traits on which natural selection can act

hardy-weinberg (HW) principle

serves as mathematical null hypothesis for study of evolutionary processes; predicts genotype and allele frequencies for next gen

hardy- weinberg equilibrium (HWE) principle

frequencies are in if they conform to predictions of the next generation; frequencies remain constant

5 assumptions about behavior of populations of the Hardy-Weinberg model

random mating, no natural selection, no genetic drift, no gene flow, no mutation

4 steps to determine if a population is in HWE

estimate genotype frequencies, calculate observed allele frequencies, calculate genotypes expected, compare observed and expected values

nonrandom mating

in nature, mating may not be random with respect to any particular gene or phenotype; changes genotype frequencies, not allele frequencies; not evolutionary process itself

assortative mating

individuals with similar phenotypes or genotypes are more likely (positive) or less likely (negative) to mate with each other; type of nonrandom mating

inbreeding

nonrandom mating between relatives; does not cause evolution (allele frequencies don’t change)

self-fertilization (selfing)

most extreme form of inbreeding; in general increases homozygotes and decreases heterozygotes; homozygous produce all homozygous offspring; heterozygous produce homo and hetero offspring (1:2:1); type of nonrandom mating

sexual selection

organism actively choses a certain mate based on physical and/or behavioral traits; form of nonrandom mating, but leads to change in allele frequencies, so is also natural selection

intrasexual selection

traits such as bright colors, long horns, and elaborate courtship displays; may improve ability to compete for mates

intersexual selection

traits make one more attractive to the opposite sex