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Chapter 23
Ch. 23
31
Biology
12th Grade
11/12/2012

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Term
Average Heterozygosity
Definition
Average percent of population's loci that are heterozygous.
Term
Balanced polymorphism
Definition
The ability of natural selection to maintain diversity in a population
Term
Balancing selection
Definition
Natural selection that maintains stable frequencies of two or more phenotypic forms in a population (balanced polymorphism).
Term
Bottleneck effect
Definition
Genetic drift in a population, usually from a natural disaster, such that the new population is not representative of the old one
Term
Cline
Definition
A graded variation in a trait that mirrors gradient variation in the environment
Term
Directional selction
Definition
Natural selection that favors individuals on the top of the phenotypic range
Term
Disruptive selection
Definition
Favors individuals on both extremes of the phenotypic range
Term
Fitness
Definition
Contribution an individual makes to the gene pool of the next generation, relative to other individuals
Term
Founder effect
Definition
Genetic drift occurring when a few individuals become isolated from a larger population
Term
Frequency-dependent selection
Definition
A decline in the reproductive success of a morph resulting from the morph’s phenotype becoming too common in a population; a cause of balanced polymorphism in populations.
Term
Gene flow
Definition
Genetic additions or subtractions from a population
Term
Gene pool
Definition
Total aggregate genes in a population
Term
Genetic drift
Definition
Fluctuations in allele frequencies because of a population's size
Term
Genetic polymorphism
Definition
Existence of two or more distinct alleles at a given locus
Term
Geographic variation
Definition
Differences in gene pools
Term
Hardy-Weinberg equilibrium
Definition
Describes a population that is not evolving
Term
Hardy-Weinberg theorem
Definition
The principle that frequencies of alleles and genotypes in a population remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.
Term
Heterozygote advantage
Definition
Preserves variation because of greater reproductive success
Term
Intersexual selection
Definition
Individuals of one sex are choosy in choosing their mate
Term
Intrasexual selection
Definition
Competition for mates
Term
Microevolution
Definition
Change in the genetic makeup of a population
Term
Modern synthesis
Definition
A comprehensive theory of evolution emphasizing populations as units of evolution and integrating ideas from many fields, including genetics, statistics, paleontology, taxonomy, and biogeography.
Term
Mutation
Definition
Rare change in the DNA of a gene
Term
Neutral variation
Definition
Variation that carries no selective advantage
Term
Phenotypic polymorphism
Definition
The existence of two or more distinct morphs (discrete forms), each represented in a population in high enough frequencies to be readily noticeable
Term
Polymorphism
Definition
Coexistence of two or more distinct forms in a population
Term
Population
Definition
Localized group capable of interbreeding and creating fertile offspring
Term
Population genetics
Definition
Study of population genetics
Term
Pseudogene
Definition
A DNA segment very similar to a real gene but which does not yield a functional product; a gene that has become inactivated in a particular species because of mutation
Term
Sexual dimorphism
Definition
A special case of polymorphism based on the distinction between the secondary sex characteristics of males and females
Term
Stabilizing selection
Definition
Favors intermediate variants instead of extreme phenotypes
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