Chapter 19: Evolutionary Change in Populations

Natural selection

________ causes changes in allele frequencies that lead to adaptation.

Hardy Weinberg

In the ________ equation, p= the frequency of the dominant allele, q= the frequency of the recessive allele, and p + q= 1.

Gene flow

________, a movement of alleles caused by the migration of individuals between populations, causes changes in allele frequencies.

Microevolution

________ is a change in allele or genotype frequencies within a population over successive generations.

Mutations

________ increase the genetic variability acted on by natural selection.

genotype frequencies

A cline is a gradual change in a species phenotype and ________ through a series of geographically separate populations.

Heterozygote advantage

________ occurs when the heterozygote exhibits greater fitness than either homozygote.

sudden decrease

A(n) ________ in population size caused by adverse environmental factors is known as a bottleneck.

Assortative mating

In ________ individuals select mates by their phenotypes.

Genetic drift

________ decreases genetic variation within a population, and the changes caused by ________ are usually not adaptive.

Directional selection

________ favors one phenotypic extreme over another, causing a shift in the phenotypic mean.

Hardy Weinberg

The ________ principle applies only if mating is random in the population, there are no net mutations that change the allele frequencies, the population is large, individuals do not migrate between populations, and natural selection does not occur.

Natural selection

________ operates on an organisms phenotype, but it changes the genetic composition of a population in a favorable direction for a particular environment.

genotype frequency

A(n) ________ is the proportion of a particular genotype in the population.

Hardy Weinberg

The ________ principle states that allele and genotype frequencies do not change from generation to generation (no evolution is occurring) in a population at genetic equilibrium.

In frequency

dependent selection, a genotypes selective value varies with its frequency of occurrence