Ch 12 Flashcards
fitness values before such standardization are values
absolute fitness
metaphor for the relationship between mean fitness of a population and the allele frequencies at one or more loci that affect fitness. possible populations with allele frequencies that max mean fitness are represented as peaks on the metaphorical landscape
adaptive landscape
allele frequency, or combination of allele frequencies at two or more loci, at which the mean fitness of a population has a (local) max. also the mean phenotype that max mean fitness
valley is when it has a min.
adaptive peak/valley
source of natural selection that opposes another source of selection on a trait
antagonistic selection
elimination of deleterious mutations in a region of the genome; may explain low levels of neutral sequence variaiton
background selection
form of natural selection that maintains polymorphism at a locus within a population
balancing selection
proportion by which the avg fitness of individuals of one genotype differs from that of a reference genotype
coefficient of selection
selection for a value of a character that is higher or lower than its current mean value
directional selection
selection in favor of two or more modal phenotypes and against those intermediate between them
diversifying selection
success of an entity in reproducing; hence the avg contribution of an allele or genotype to the next generation or to succeeding generation
fitness
mode of natural selection in which the fitness of each genotype varies as a function of its frequency in the population
frequency-dependent selection
manifestation of higher fitness by heterozygotes than by homozygotes at a specific locus
heterozygote (dis)advantage
test for selection at a locus by comparing DNA sequence variation within species with the variation among species
McDonald-Kreitman test
arithmetic avg fitness of all individuals in a population, usually relative to some standard
mean fitness
stable variation at a locus owing to superior fitness of different genotypes under different conditions of a varying environment
multiple-niche polymorphism
constancy; more often in this book, the propensity to return to a condition or to one several such conditions
multiple stable equilibria
expression by two alleles in heterozygous condition of a phenotypic value for some character that lies outside the range of the two corresponding homozygotes
overdominance
change in the allele frequency within a population from one to another local maximum of mean fitness by passage through states of lower mean fitness
peak shift
elimination of deleterious alleles from a population
purifying selection
fitness of a genotype relative to the fitness of a reference genotype, which is often set at 1.0;
relative fitness
fitness of a genotype or other biological entity, often measured by the avg per capita number of offspring that a newly formed zygote will have, or by similar measures
reproductive success
increment in fitness provided by an allele or a character state
selective advantage
reduction or elimination of DNA sequence variation in the vicinity of a mutation that has been fixed by natural selection relatively recently
selective sweep
selection that maintains the mean of a character at or near a constant intermediate value in a population
stabilizing selection
lower fitness of a heterozygote than of both of the homozygotes for the same allele
underdominance
