Biology Chapter 16

microevolution

a change in the collective genetic material of a population

population genetics

the study of the frequency and interaction of alleles and genes in populations

bell curve

on a graph of the frequency of some variable, a curve that first rises then falls and thus forms a symmetrical bell-shaped curve

gene pool

all of the genes of he reproductively active members of a population

allele frequency

the proportion of gene copies in a population that are given allele, expressed as a percentage

phenotype frequency

the ratio of individuals with a particular phenotype to the total number of individuals in a population

Hardy-Weinberg genetic equilibrium

the principle that states that the frequency of alleles in a population does not change over generations unless outside forces act on the population

equilibrium

in biology, a state that exists when the concentration of a substance is the same throughout a space

immigration

the movement of an individual or group into an area

emigration

the movement of an individual or group out of an areaa

gene flow

the movement of genes into or out or a population due to interbreeding

genetic drift

the random change in allele frequency in a population

sexual selection

an evolutionary mechanism by which traits that increase the ability of individuals to attract or acquire mates appear with increasing frequency in a population

stabilizing selection

a type of natural selection in which the average form of a trait is favored and becomes more common

disruptive selection

a type of natural selection in which two extreme forms of a trait are selected

directional selection

a type of natural selection in which the most extreme form of a trait is favored and becomes more common

speciation

the formation of new species as a result of evolution

morphology

the study of the structure and form of an organism

biological species concept

the concept that a species is a population of organisms that can interbreed but cannot breed with other populations

geographic isolation

the physical separation of populations due to geographic barriers that prevent interbreeding

allopatric speciation

species arise as a result of geographic isolation

reproductive isolation

the inability of members of a population to successfully interbreed with members of another population of the same or a related species

prezygotic isolation

occurs before fertilization

postzygotic isolation

occurs after fertilization

sympatric speciation

occurs when two subpopulations become reproductively isolated within the same geographic area

gradualism

a model of evolution in which gradual change over a lond period of time leads to biological diversity

punctuated equilibrium

a model of evolution in which short periods of drastic change in species-mass extinction, rapid speciation-separated by long periods of little of no change