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