Biology » Evolution of Populations » Population Genetics

Summarizing Population Genetics

Summary

Both genetic and environmental factors can cause phenotypic variation in a population. Different alleles can confer different phenotypes, and different environments can also cause individuals to look or act differently. Only those differences encoded in an individual’s genes, however, can be passed to its offspring and, thus, be a target of natural selection. Natural selection works by selecting for alleles that confer beneficial traits or behaviors, while selecting against those for deleterious qualities.

Genetic drift stems from the chance occurrence that some individuals in the germ line have more offspring than others. When individuals leave or join the population, allele frequencies can change as a result of gene flow. Mutations to an individual’s DNA may introduce new variation into a population. Allele frequencies can also be altered when individuals do not randomly mate with others in the group.

Glossary

assortative mating

when individuals tend to mate with those who are phenotypically similar to themselves

bottleneck effect

magnification of genetic drift as a result of natural events or catastrophes

cline

gradual geographic variation across an ecological gradient

gene flow

flow of alleles in and out of a population due to the migration of individuals or gametes

genetic drift

effect of chance on a population’s gene pool

genetic variance

diversity of alleles and genotypes in a population

geographical variation

differences in the phenotypic variation between populations that are separated geographically

heritability

fraction of population variation that can be attributed to its genetic variance

inbreeding

mating of closely related individuals

inbreeding depression

increase in abnormalities and disease in inbreeding populations

nonrandom mating

changes in a population’s gene pool due to mate choice or other forces that cause individuals to mate with certain phenotypes more than others

population variation

distribution of phenotypes in a population

selective pressure

environmental factor that causes one phenotype to be better than another

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