Evolution- Bio Test 3

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Author:
bamasi
ID:
246739
Filename:
Evolution- Bio Test 3
Updated:
2013-11-13 15:40:12
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bio
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bio
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  1. Hardy-Weinberg assumptions
    • 1- population is large
    • 2- random mating occurs
    • 3- no mutation takes place
    • 4- no migration
    • 5- no selection occurs
  2. definition for evolution
    • change through time
    • decent with modification
    • change in gene frequencies through time
  3. agents of evolutionary change
    • mutation
    • gene flow
    • nonrandom mating
    • genetic drift
    • selection
  4. mutation
    • ultimate source of variation 1-10 times per 100,000 cell divisions
    • natural selection does not affect mutation rate
  5. gene flow
    • the movement of alleles from one population to another (ie, migration)
    • low levels of gene flow homogenize allele frequencies among populations
  6. nonrandom mating
    • certain genotypes are more likely to mate than others
    • inbreeding- mating with relatives increases homogyzosity 
    • outcrossing- opposite of inbreeding increases proportion of heterozygosity 
    • neither change allele frequencies
  7. genetic drift
    • random changes by chance (most frequent in small populations)
    • leads to a loss of alleles in isolated populations
    • 2 types: founder effect; bottleneck (drastic reduction in population) effect
  8. selection
    • the result of differential fitness
    • artificial vs. natural
  9. 3 conditions for natural selection
    • 1. phenotypic variation must exist
    • 2. phenotypic variation results in different reproductive success
    • 3. variation must be genetically inherited (i.e., phenotype linked to genotype)
  10. forms of selection
    • disruptive
    • directional
    • stabilizing
  11. evidences
    • fossil record
    • molecular record
    • homology
    • divergent evolution
    • vestigial structures
    • development
  12. species
    group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups
  13. reproductive isolation
    • when individuals cannot produce fertile offspring
    • 2 types: prezygotic, postzygotic
  14. prezygotic isolating mechanisms
    • prevents the formation of zygotes 
    • -ecological isolation (e.g., toads)
    • -behavioral isolation (e.g., mating rituals)
    • -temporal isolation
    • -mechanical isolation
  15. postzygotic isolation mechanisms
    • hybrids fail to develop or cannot become established in nature
    • -e.g., leopard frogs
  16. speciation
    the formation of two descendant species from one ancestral species
  17. how can adaptation (natural selection) lead to speciation?
    it cannot unless Gene Flow is zero or very near zero
  18. what can lead to no gene flow?
    • continental drift
    • glacier expansion and retreat
    • stream course change
    • colonization of remote areas
    • -often combined with genetic drift
    • mountain upwelling
  19. allopatric speciation
    when populations are geographically separated
  20. sympatric speciation
    • when populations are together
    • -much less common
  21. examples of sympatric speciation
    • many plants readily hybridize 
    • -usually are infertile
    • -polyploidy can lead to fertility
    • --it is estimated that 80% of grass species are polyploid species
    • e.g., Tragopogon (goat's beard)

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