30 terms

AP Bio Chapter 23 Vocabulary

evolutionary change on its smallest scale
population genetics
the study of how populations change genetically over time
modern synthesis
a comprehensive theory of evolution that integrated ideas from many other fields
a localized group of individuals that are capable of interbreeding and producing fertile offspring
gene pool
the aggregate of genes in a population at any one time is called the population's ______ _______
Hardy-Weinberg theorem
states that the frequencies of alleles and genotypes in a population's gene pool remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work
Hardy-Weinberg equilibrium
the condition describing a non-evolving population, which follows these 5 conditions: large population, no gene flow, no mutations, random mating, no natural selection
change in the nucleotide sequence of DNA
genetic drift
similar deviations from the expected result explain how allele frequencies can fluctuate unpredictably from one generation to the next
bottleneck effect
when a sudden change in the environment may drastically reduce the size of a population, the survivors may have passed through a restrictive "bottleneck", and their gene pool may no longer be reflective of the original population's gene pool
founder effect
when a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool isn't reflective of the source population
gene flow
genetic additions to and/or subtractions from a population resulting from the movement of fertile individuals or gametes
phenotypic polymorphism
a population is said to display ________ ________ for a character if two or more distinct morphs are each represented in high enough frequencies to be readily noticeable
average heterozygosity
the percent, on average, of a population's loci that are heterozygous in members of the population
geographic variation
differences between the gene pools of separate populations or population subgroups
a graded change in a trait along a geographic axis
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
relative fitness
the contribution of a genotype to the next generation comparted to the contributions of alternative genotypes for the same locus
directional selection
__________ ________ is most common when a population's environment changes or when members of a population migrate to a new habitat with different environmental conditions from their former one
disruptive selection
________ ________ occurs when conditions favor individuals on both extremes of a phenotypic range over individuals with intermediate phenotype
stabilizing selection
_________ _________ acts against extreme phenotypes and favors intermediate variants
balancing selection; balanced polymorphism
_________ ________ occurs when natural selection maintains stable frequencies of two or more phtnotypic forms in a population, a state called ___________ _________
heterozygote advantage
if individuals who are heterozygous at a particular gene locus have greater fitness than the homozygous, natural selection will tend to maintain two or more alleles at that locus
frequency-dependent selection
the fitness of any one morph that declines if it becomes too common in the population
neutral variation
some of the genetic variation in populations probably has little or no impact on reproductive success, and thus natural selection doesn't affect those alleles
genes that have become inactivated by mutations
sexual selection
natural selection for mating success
sexual dimorphism
marked differences between the sexes in secondary sexual characteristics, which are not directly associated with reproduction
intrasexual selection
(selection "within the same sex") is a direct competition amon individuals of one sex for mates of the opposite sex
intersexual selection
individuals of one sex (usually females) are choosy in selecting their mates from the other sex