Unit 9 - Chapter 23 - The Evolution of Populations
Terms
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- microevolution
- evolutionary change on its smallest scale
- 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
- sexual selection
- natural selection for mating success
- disruptive selection
- ________ ________ occurs when conditions favor individuals on both extremes of a phenotypic range over individuals with intermediate phenotype
- gene pool
- the aggregate of genes in a population at any one time is called the population's ______ _______
- 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
- 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
- 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
- cline
- a graded change in a trait along a geographic axis
- pseudogenes
- genes that have become inactivated by mutations
- gene flow
- genetic additions to and/or subtractions from a population resulting from the movement of fertile individuals or gametes
- frequency-dependent selection
- the fitness of any one morph that declines if it becomes too common in the population
- genetic drift
- similar deviations from the expected result explain how allele frequencies can fluctuate unpredictably from one generation to the next
- intrasexual selection
- (selection "within the same sex") is a direct competition amon individuals of one sex for mates of the opposite sex
- sexual dimorphism
- marked differences between the sexes in secondary sexual characteristics, which are not directly associated with reproduction
- intersexual selection
- individuals of one sex (usually females) are choosy in selecting their mates from the other sex
- modern synthesis
- a comprehensive theory of evolution that integrated ideas from many other fields
- fitness
- the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
- population
- a localized group of individuals that are capable of interbreeding and producing fertile offspring
- population genetics
- the study of how populations change genetically over time
- 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
- 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
- mutations
- change in the nucleotide sequence of DNA
- average heterozygosity
- the percent, on average, of a population's loci that are heterozygous in members of the population
- 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
- balancing selection; balanced polymorphism
- _________ ________ occurs when natural selection maintains stable frequencies of two or more phtnotypic forms in a population, a state called ___________ _________
- stabilizing selection
- _________ _________ acts against extreme phenotypes and favors intermediate variants
- geographic variation
- differences between the gene pools of separate populations or population subgroups
- 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
- relative fitness
- the contribution of a genotype to the next generation comparted to the contributions of alternative genotypes for the same locus