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Evolution of Populations

Evolution of Populations. 2010. The Modern Synthesis. Population genetics integrates Darwinian evolution and Mendelian Genetics Important terms in population genetics: Population: group of individuals of same species

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Evolution of Populations

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  1. Evolution of Populations 2010

  2. The Modern Synthesis • Population genetics integrates Darwinian evolution and Mendelian Genetics • Important terms in population genetics: Population: group of individuals of same species Species: groups of populations that are capable of interbreeding and producing fertile offspring in nature Gene pool: total aggregate of genes in a population

  3. Hardy – Weinberg Theorem • Gene pool of non-evolving population • States that the frequency of alleles and genotypes in a population’s gene pool remain constant unless acted upon by agents other than Mendelian segregation and recombination of alleles. p+q = 1 Hardy Weinberg Equilibrium: p2 + 2pq + q2 = 1 P2 = Frequency of RR phenotype 2pq -= Frequency of Rr phenotype q2= Frequency of rr phenotype

  4. Conditions that must be met: Very large population size. No migration No net mutations Random mating No natural selection Do you that any natural populations are in Hardy-Weinberg equilibrium?

  5. Microevolution • Generation to generation change in the population’s frequency of alleles • 2 main causes: genetic drift – change due to chance, small populations & natural selection • Other causes -

  6. Bottleneck Effect • Drastically reduced population sizes • Small population size may not be representative of original gene pool • Reduction in genetic variablility

  7. The Founder Effect Occurs when a few individuals colonize an isolated habitat from a larger population

  8. Gene Flow • Genetic exchange through migration – gain or loss of alleles

  9. Mutation Substitutes one allele for another

  10. Selection Types

  11. Sexual Selection

  12. Speciation – Biological Species Concept • Prezygotic Barriers: habitat isolation, behavioral isolation, temporal isolation, mechanical isolation, gametic isolation • Postzygotic Barriers: reduced hybrid viability, reduced hybrid fertility, hybrid breakdown

  13. Types of Speciation • Allopatric: geographic barriers, disruption of gene flow • Sympatric: genetic causes – polyploid (plants), other genetic factors

  14. Tempo of Evolution • Darwin – gradual continual rate • Punctuated equilibrium model: spurts of rapid change followed by periods of relatively little change (Ex. Species exists for 5 million years but most morphological changes in 50,000 yrs – just 1%).

  15. Phylogenies • Many lines of evidence compiled • Biogeographical, fossil, morphological similarities (homologous not analogous structures), genetic evidence

  16. Categories of Evolution • Convergent evolution - acquisition of the same biological trait in unrelated lineages. • Leads to analogous structures

  17. Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades

  18. Divergent evolution - accumulation of differences between groups which can lead to the formation of new species, usually a result of diffusion of the same species adapting to different environments

  19. Major Lineages of Life 3 domains: Bacteria, Eukaryota, Arachae

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