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AP Bio Chapter 23, 9e
Vocab
23
Biology
12th Grade
11/12/2012

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Term
average heterozygosity
Definition
percentage, on average, of a population's loci that are heterogeneous in members of the population.
Term
balancing selection
Definition
Natural selection that maintains two or more phenotypic forms in a population.
Term
bottleneck effect
Definition
genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. Typically, the surviving population is no longer genetically representative of the original population.
Term
cline
Definition
a graded change in a character along a geographic axis
Term
directional selection
Definition
Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.
Term
disruptive selection
Definition
Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes.
Term
founder effect
Definition
Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.
Term
gene flow
Definition
The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes.
Term
gene pool
Definition
The aggregate of all copies of every type of allele at all loci in every individual in a population. The term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population.
Term
genetic drift
Definition
A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects of genetic drift are most pronounced in small populations.
Term
genetic variation
Definition
Differences among individuals in the composition of their genes or other DNA segments.
Term
geographic variation
Definition
Differences between the gene pools of geographically separate populations or population subgroups.
Term
Hardy-Weinberg principle
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
Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool.
Term
intersexual selection
Definition
Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.
Term
intrasexual selection
Definition
Selection in which there is direct competition among individuals of one sex for mates of the opposite sex.
Term
microevolution
Definition
Evolutionary change below the species level; change in the allele frequencies in a population over generations.
Term
neutral variation
Definition
Genetic variation that does not provide a selective advantage or disadvantage.
Term
popilation
Definition
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.
Term
relative fitness
Definition
The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population.
Term
sexual dimorphism
Definition
Differences between the secondary sex characteristics of males and females.
Term
sexual selection
Definition
A form of selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
Term
stabilizing selection
Definition
Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes.
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