Evolution Terms

evolution

decent with modification

biological evolution

change in allele or genotype frequencies in populations over time

polymorphism

distinct variants of character

population

a group of individuals of the same species that live in the same area and interbreed producing fertile offspring

gene pool

sum of all alleles at all gene loci in all individuals within a population

Hardy-Weinberg Principle

no mutation, no gene flow, large population, no natural selection, random mating

mutation

a heritable change in DNA

gene flow

change in allele frequencies as individuals join a population and reproduce

genetic drift

random changes in allele frequencies caused by chance events

natural selection

differential survivorship or reproduction of individuals with different genotypes

population bottleneck

reduction in alleles due to population reduction

founder effect

reduced genetic diversity when a small population splits from the main population and interbreeds with a smaller gene pool resulting in little genetic variation

relative fitness

contribution of an individual to the gene pool in the next generation relative to the contribution of others

directional selection

favours individuals near one end of the phenotypic spectrum

stabilizing selection

favours individuals with intermediate phenotypes

disruptive selection

favours individuals with extreme phenotypes

sexual selection

competition for mates

balancing selection

different forms of selection that lead to active maintenance
of genetic variation in a population

balanced polymorphisms

maintained genotypic variation

heterozygote advantage

heterozygotes have higher fitness than homozygotes and their reproduction maintains the homozygote population

frequency dependent selection

fitness of a genotype increases as its frequency decreases

vestigial structures

structures that have no function and appear to be the evolutionary left overs of a past ancestor

morphology

the study of size, shape and structure of various organisms to show how they are related