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ch.23

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Terms in this set (22)

  • Smallest unit of evolution
    The population is the smallest unit of evolution because evolution occurs as changes in allele frequencies within populations over time.
  • Source of genetic variation in populations
    Genetic variation arises through mutations, gene flow, and sexual reproduction. It is necessary for natural selection to act on.
  • Why genetic variation is necessary for natural selection
    Without genetic variation, natural selection cannot favor certain traits, so populations cannot adapt or evolve.
  • Hardy-Weinberg equilibrium purpose
    Used to calculate allele and genotype frequencies in a population and to determine if evolution is occurring.
  • Five conditions for Hardy-Weinberg equilibrium
    No mutation, random mating, no gene flow, infinite population size, and no natural selection.
  • What happens if Hardy-Weinberg conditions are not met
    Allele and genotype frequencies change over time, indicating that evolution is occurring.
  • Directional natural selection
    Favors one extreme phenotype, causing a shift in the population's trait distribution.
  • Disruptive natural selection
    Favors both extreme phenotypes and selects against intermediate phenotypes.
  • Stabilizing natural selection
    Favors intermediate phenotypes and selects against extremes, reducing variation.
  • Balancing natural selection
    Maintains multiple alleles in the population through mechanisms like heterozygote advantage.
  • Sexual selection definition
    A form of natural selection where traits increase an individual's chances of mating.
  • Intrasexual selection
    Competition between members of the same sex for mates.
  • Intersexual selection
    Mate choice where one sex selects mates based on certain traits.
  • Is natural selection goal-oriented?
    No, natural selection is not goal-oriented and cannot produce perfect organisms.
  • Effect of genetic drift in small populations
    Genetic drift has a greater effect in small populations, causing random changes in allele frequencies.
  • Bottleneck effect
    A sudden reduction in population size that reduces genetic variation due to genetic drift.
  • Founder effect
    When a small group establishes a new population, leading to reduced genetic variation.
  • Gene flow (migration)
    Movement of alleles between populations through migration, increasing genetic variation.
  • Fitness in evolutionary terms
    An organism's ability to survive and reproduce, passing on its genes to the next generation.
  • Adaptation definition
    A heritable trait that increases an organism's fitness in its environment.
  • Microevolution vs. Macroevolution
    Microevolution is change in allele frequencies within populations; macroevolution is large-scale evolutionary changes that can lead to new species.
  • Horizontal gene transfer
    Transfer of genes between organisms in a manner other than traditional reproduction.