Chapter 23 Vocabulary

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Population Genetics

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The study of how a population changes over time

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Modern Synthesis

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A comprehensive theory of evolution emphasizing populations as units of evolution and integrating ideas from many fields, including genetics, statistics, paleontology, taxonomy and biogeography

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Gene pool

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Total aggregate of genes in a population at any one time

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Hardy-Weinburg Theorem

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the principle that frequencies of allels and geneotypes om a population remain constant from generation to generation, provided that only mendelian segregation and recombination of allels are at work

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Hardy-Weinburg Equilibrium

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The condition describing a non-evolving population( one that is in genetic equilibrium,

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Mutations

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A change in the DNA of a gene, ultimately crating gene diversity

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Duplication

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An aberration in chromosome structure, due to fusion with a fragment of a homologous chromosome, such that a portion of a chromosome is duplicated

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Genetic Drift

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unpredictable fluctuations in allel frequencies from one generation to the next because of the populations finite size

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Bottle Neck Effect

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Genetic drift resulting from the reduction od a population. typically by a natural disaster=, such that the surviving population is no longer genetically representative of the original population

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founder Effect

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Genetic drift that occurs when a few individualsbecome isolated from the larger population, with the result that the new populations gene pool is not reflective of the original population

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Gene Flow

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Genetic additions to or subtractions from a population resulting from the movement of fertile individuals of gamate

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Phenotypic Polymorphism

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The extent of two or more or more distinct morphs, each represented in a population in high enough formulas. each is represented in a population in high enough does

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Genetic Polymorpism

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The existence of two or more distinct allels at a given locus in a populations gene pool

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Average heterozygosity

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The percent on average, of a populations loci that are heterozygotous in members of the population

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geographic variation

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Differences between the gene poo of separate populations or population sub sections

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Fitness

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The contribution an individual makes to the gene pool of the next generation , realitive to the contributions of other individuals

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Relative Fitness

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The contribution of one genotype to the next generation compared to that of alternative genotypes for the same loci

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Directional Evolution

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Natural selection that favors individuals at one end of phenotypic range

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Cline

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A graded variation in a trait that parallels a gradient in the environment

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Disruptive Selection

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Natural selection that favors individuals on both extreme ends of a phenotypic range over intermediate phenotypes

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Stabilizing Selection

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Natural selection that favors intermediate variants by acting against extreme phenotypes

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Balancing Selection

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Natural selection that maintains stable frequencies of two or more phenotypic forms in a population( balanced polymorphism)

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Balanced polymorphism

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The ability of natural selection to maintain diversity in a population

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heterozygote advantage

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Freater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in the gene pool.

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Frequency-dependent selection

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A decline in reproductive success of a morph resultin from the morphs phenotype becoming too common in the population, a couse of balanced polymorphism in populations

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Neutral variation

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Genetic variation that confers no no apparent selective advantage

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pseudogenes

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A DNA segment very similar to a real gene but which does not yeild a functional product; a gene that has become inactived in a particular species because of mutation.

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sexual selection

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Natural selection for mating success

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Sexual Dimorphism

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A special case of polymorphism based onthe distinction between the secondary characteristics of males and females.

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Intrasexual selection

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A direct competition among individuals of one sex (usually the males in the vertabrated) for mates of the opposite sex.

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Intersexual/mate choice

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selection whereby individuals of one sex (females) are choosy in selecting their mates frominduviduals of the other sex

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Population

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A group of the same species in the same geographical area

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SpeciesNatural Selection

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A group or groups of interbreeding individuals that are reproductively isolated from other sucj groups

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Natural Selection

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is situational i.e. adapts a population to its immediate surroundinfs

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Microevolution

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The genetic change the generation to generation change in a populations frequency of allels or genes

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Darwin Fitness

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The ability of an individual to contribute to the gene pool of future generations.