bio ch23 key terms

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bio ch23 key terms
2013-02-21 20:15:28
evolution populations

26 terms and defs
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  1. stabilizing selection
    Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes
  2. bottleneck effect
    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.
  3. gene pool
    The aggregate of all of the alleles for all of the loci in all individuals 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.
  4. gene flow
    The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes.
  5. geographic variation
    Differences between the gene pools of geographically separate populations or population subgroups.
  6. founder effect
    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
  7. sexual selection
    A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
  8. intrasexual selection
    A direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex.
  9. average heterozygosity
    (het'-er-o-zi-go'-si-te) The percent, on average, of a population's loci that are heterozygous in members of the population.
  10. duplication
    An aberration in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is duplicated.
  11. heterozygote advantage
    Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool.
  12. hardy-weinberg principle
    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.
  13. sexual dimorphism
    (di-mor'-fizm) Marked differneces between the secondary sex characteristics of males and females.
  14. diruptive selection
    Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes.
  15. balancing selection
    Natural selection that maintains two or more phenotypic forms in a population.
  16. microevolution
    Evolutionary change below the species level; change in the allele frequencies in a population over generations.
  17. hardy-weinberg equilibrium
    The condition describing a nonevolving population (one that is in genetic equilibrium)
  18. population
    A localized group of individuals of the same species that can interbreed, produced fertile offspring.
  19. genetic drift
    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.
  20. cline
    A graded change in a character along a geographic axis.
  21. frequency-dependent selection
    A decline in the reproductive success of individuals that have a phenotype that has become too common in a population.
  22. neutral variation
    Genetic variation that does not appear to provide a selective advantage or disadvantage.
  23. relative fitness
    The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population.
  24. mutation
    (myu-ta'-shun) A change in the nucleotide sequence of an organism's DNA, ultimately creating genetic diversity. Mutations also can occur in the DNA or RNA of a virus.
  25. interselection selection
    Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.
  26. directional selection
    Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.