Stabalizing Selection

Mode of natural selection by which intermediate phenotypes in the range of variation are favored and extremes at both ends are eliminated.

Sexual Selection

A microevolutionary process; a type of selection that favors a trait giving an individual a competitive edge in attracting or keeping a mate (favors reproductive success).

Population

All individuals of the same species that are occupying a specified area.

Polymorphism

The persistence of two or more qualitatively different forms of a trait (morphs) in a population.

Natural Selection

Microevolutionary process; the outcome of differences in survival and reproduction among individuals that differ in details of heritable traits.

Lethal Mutation

Mutation with drastic effects on phenotype; usually causes death.

Inbreeding

Nonrandom mating among close relatives that share many identical alleles.

Genetic Equilibrium

In theory, a state in which a population is not evolving. Compare Hardy-Weinberg rule.

Genetic Drift

Change in allele frequencies over the generations due to chance alone. Its effect is most pronounced in very small populations.

Gene Pool

All genotypes in a population.

Gene Flow

Microevolutionary process; alleles enter and leave a population as an outcome of immigration and emigration, respectively.