BIO 3400 Scioli
Summer II 1999

Objectives / Review for Exam III - new material, part 2

  1. Population genetics
    1. allele frequency, genotype frequency
    2. polymorphism
    3. heterozygosity
    4. Hardy-Weinberg equilibrium
      1. case 1: one locus, two alleles
      2. case 2: one locus, many alleles
    5. assumptions of H-W equilibrium
      1. infinite population size
      2. closed population (no migration)
      3. no mutation
      4. no selection
        1. no differential survivorship to reproductive maturity
        2. no differential fecundity
      5. random mating
    6. violation of the assumptions
      1. population size
        1. actual (N) versus effective (Ne) population size
        2. sampling errors
          1. population bottleneck
          2. founder event
          3. genetic drift
      2. migration
      3. mutation
      4. selection
        1. fitness / components of fitness
        2. selection for / against alleles
          • heterosis / overdominance / heterozygote advantage / hybrid vigor
          • balanced polymorphism
        3. nonrandom mating
          • selfing
          • inbreeding
          • assortative mating
          • Wahlund effect (deficiency of heterozygotes which indicates two subpopulations)
  2. Natural selection
    1. conditions required for natural selection
      1. phenotypic variation must exist among individuals within a population
      2. this phenotypic variation must adaptive, i.e., it must affect fitness
      3. this phenotypic variation must be heritable (under genetic control)
    2. production of more offspring than can survive can speed the rate of natural selection; however, this is NOT a requirement for the operation of natural selection
    3. the rate of response to natural selection on a trait is directly proportional to the amount of genetic variation present in the population for that trait = Fisher's Fundamental theorem of Natural Selection
    4. sexually-reproducing organisms generate genetic variation through
      1. mutation (can create new alleles)
      2. crossing-over in prophase I of meiosis
      3. random segregation of parental homologues in anaphase I of meiosis
      4. random recombination of gametes in fertilization
    5. selection on quantitative traits
      1. stabilizing selection
      2. directional selection
      3. disruptive selection
  3. Population growth
    1. J-shaped curve
      • exponential growth, unlimited resources
    2. S-shaped curve
      • logistic growth, resources limitation (carrying capacity = k)
    3. Thomas Malthus' influence on Darwin's thinking
    4. struggle for existence
      1. most organisms produce many more offspring than can survive
      2. survivors are determined by a non-random process based on adaptation

This is not intended to be an exhaustive transcript of everything discussed in class; however, major topics not listed here will not be covered on the exam. It is intended as a guide to help in your preparation for the exam. When in doubt about the details, look first to your class notes, then check out the index at the back of your textbook(s).


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