Bio wb Ch 17

population genetics

the study of frequency and interactions of alleles and genes in population

normal distribution

a line graph showing the general trends in a set of data of which most values are near the mean

frequency

the proportion or ratio of a group that is of one type

genotype frequencies

focuses on the ratio of homozygous dominate:heterozygous:homozygous recessive

allele frequencies

focuses on the ratio of the dominant allele to the recessive allele of a particular characteristic

generate

produce; bring into being; cause to be

genetic equilibrium

the state in which the allele frequencies of a population remain in the same ratios from one generation to the next

Hardy-Weinberg principle

this idea predicts that the frequencies of alleles and genotypes in a population will not change unless at least one of 5 forces acts upon the population

gene flow

this occurs when genes are added to or removed from a population

nonrandom mating

occurs when any limits or preferences are placed on mate choices

genetic drift

this occurs when chance events cause rare alleles to be lost from one generation to the next

mutation

this can cause the addition of a new allele to a population

deviate

to turn aside; to diverge or differ

indirect force

natural selection acts on genotypes by removing unsuccessful phenotypes from a population

directional selection

a pattern of natural selection whose normal distribution peak moves in one direction along its range

stabilizing selection

a pattern of natural selection whose normal distribution peak becomes narrower

disruptive selection

a pattern of natural selection whose normal distribution peak undergoes a change that pushes it apart in different directions to form two new peaks

speciation

occurs when the net effects of evolutionary forces result in a population that has unique features and is reproductively isolated

reproductive isolation

a state in which two populations can no longer interbreed to produce future offspring

geography

the mechanism of isolation where a physical barrier may arise between populations which prevents interbreeding

ecological niche

the mechanism of isolation where divergence can occur due to populations using different niches

mating behavior and timing

the mechanism of isolation where two populations develop differences in how and/or when to reproduce

polyploidy

the mechanism of isolation where an organism has received a duplicate set of chromosomes by accident and become reproductively isolated from a population yet be able to reproduce itself via vegetative growth, self-fertilization, or find a polyploidy mate.

hybridization

the mechanism of isolation where two closely related species may come back into contact with each other and attempt to mate