The Evolution of Populations: Vocabulary Practice

Gene Pool

The combined alleles of all the individuals of a population

Allele Frequency

A measure of how common a certain allele is in a population

Normal Distribution

The type of distribution in which the frequency if highest near the mean value and decreases toward each extreme end of the range


The observable change in the allele frequencies of a population over time

Directional Selection

A type of selection in that favors phenotypes at one extreme of a trait's range

Stabilizing Selection

When the intermediate phenotype is favored and becomes more common in the population

Disruptive Selection

When both extreme phenotypes are favored

Genetic Drift

The changes in allele frequencies that are due to chance

Bottleneck Effect

Genetic drift that occurs after an event greatly reduces the size of a population

Founder Effect

A genetic drift that occurs after after a small number of individuals colonize a new area

Sexual Selection

Occurs when certain traits increase mating success

Hardy-Weinberg Equillibrium

Condition in which a population's allele frequencies for a given trait do not change from generation to generation

Reproductive Isolation

Occurs when members of different populations can no longer mate successfully


The rise of two or more species from one existing species

Behavioral Isolation

Isolation caused by differences in courtship or mating behaviors

Geographic Isolation

Involves physical barriers that divide a population into two or more groups

Temporal Isolation

Exists when timing prevents reproduction between populations

Convergent Evolution

Evolution toward similar characteristics in unrelated species

Divergent Evolution

When closely related species evolve in different directions


The process in which two or more species evolve in response to changes in each other


The elimination of a species from Earth

Punctuated Equilibrium

States that all episodes of speciation occur suddenly in geologic time and are followed by long periods of little evolutionary change

Adaptive Radiation

The diversification of one ancestral species into many descendant species

Gene Flow

The movement of alleles from one population to another