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16 terms

Ch. 16 Evolution of Populations

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gene pool
consists of all genes, including all the different alleles, that are present in a population
relative frequency
the number of times that the allele occurs in a gene pool compared with the number of times other alleles for the same gene occur
single-gene trait
traits controlled by a single gene that has two alleles
polygenic trait
traits controlled by two or more genes of a polygenic trait usually with two or more alleles
directional selection
form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness that indivduals in the middle or at the other end of the curve
stabilizing selection
form of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end
disruptive selection
form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle
genetic drift
random change in allele frequencies that occurs in small populations
founder effect
change in allele frequencies as a result of the migration of a small subgroup of a population
Hardy-Weinberg principle
principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change
genetic equilibrium
situation in which allele frequencies remain constant
speciation
formation of new species
reproductive isolation
separation of species or populations so that they cannot interbreed and produce fertile offspring
behavioral isolation
form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding
geographic isolation
form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water
temporal isolation
form of reproductive isolation in which two populations reproduce at different times