Chapter 23.Key
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Chapter 23.Key

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Chapter 23.Key Chapter 23.Key Presentation Transcript

  • The Evolution of Populations Chapter 23
  • THE HARDY WEINBERG THEOREM: applies for gene pool of non evolving population: very large population size no migration no net mutations random mating no natural selection
  • THE HARDY WEINBERG THEOREM p 2 + 2pq + q2 =1 frequency of frequency frequency of RR genotype Rr plus rR of rr where p is frequency of one allele (R) q is frequency of the other allele (r)
  • CAUSES OF MICROEVOLUTION microevolution: occurance of small scale changes in alle frequencies in a population, over a few generations
  • CAUSES OF MICROEVOLUTION Genetic Drift: a change in a small population’s allele frequencies due to change ~ bottleneck effect: drastic reduction in population size because of disaster; the survivors makes up new frequencies of alleles b/c they are unlikely represent original gene pool ~ founder effect: when few individuals colonize new area
  • CAUSES OF MICROEVOLUTION Natural Selection: individuals with favorable phenotypes are more successful in producing offspring -> favorable genotypes are increased, thus causing microevolution Gene flow: migration or transfer of fametes between populations Mutations: changes in nucleotide sequences
  • NATURAL SELECTION Relative Fitness: Contribution an organism makes to the gene pool of the next generation relative to other members.
  • Directional Selection: Individuals at one extreme are favored. Disruptive Selection: Individuals at both extremes are favored. Stabilizing Selection: Acts against both extremes and favors extremediates.
  • Sexual selection may lead to pronounced secondary differences between the sexes.