The Evolution of Populations
19.1 Population Evolution
Genetic variation in a population is determined by mutations, natural selection, genetic drift, genetic hitchhiking, and gene flow.
Population genetics studies changes in an allele frequency in a population's gene pool, as well as the various methods by which this occurs.
Hardy-Weinberg Principle of Equilibrium
The Hardy-Weinberg Principle can be used to estimate the frequency of alleles and genotypes in a population..
19.2 Population Genetics
Genetic variance is a measure of the variation that exists in the genetic makeup of individuals within population.
Genetic drift is the change in allele frequencies of a population due to random chance events, such as natural disasters.
Gene Flow and Mutation
The gene structure within a population can change as individuals migrate into or out of a population.
Nonrandom Mating and Environmental Variance
Population structure can be altered by nonrandom mating (the preference of certain individuals for mates) as well as the environment.
19.3 Adaptive Evolution
Natural selection drives adaptive evolution by selecting for and increasing the occurrence of beneficial traits in a population.
Stabilizing, Directional, and Diversifying Selection
Stabilizing, directional, and diversifying selection either decrease, shift, or increase the genetic variance of a population.
In frequency-dependent selection, phenotypes that are either common or rare are favored through natural selection.
Sexual selection, the selection pressure on males and females to obtain matings, can result in traits designed to maximize sexual success.
No Perfect Organism
Natural selection cannot create novel, perfect species because it only selects on existing variations in a population.