Bio Exam 3

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  1. 3 conditions for natural selection
    • phenotypic variation must exist
    • phenotypic variation results in different reproductive success
    • variation must be genetically inherited (phenotype linked to genotype)
  2. forms of selection
    • disruptive selection
    • directional selection
    • stabilizing selection
  3. evidences of evolution
    • fossil record
    • molecular record
    • homology
    • divergent evolution
    • vestigial structures
    • development
  4. biological species concept
    species- group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups
  5. reproductive isolation
    • when individuals cannot produce fertile offspring     
    • 2 types     
    • 1) prezygotic     
    • 2) postzygotic
  6. prezygotic isolating mechanisms
    • prevents the formation of zygots
    • ex. ecological isolation; behavioral isolation; temporal isolation; mechanical isolation
  7. postzygotic isolating mechanisms
    • hybrids fail to develop or cannot become established in nature
    • ex. leopard frogs
  8. speciation
    the formation of two descendant species from one ancestral species
  9. how can adaptation (natural selection) lead to speciation?
    it cannot unless gene flow is zero or very near zero
  10. Hardy-Weinberg assumptions
    • 1- population is large
    • 2- random mating occurs
    • 3- no mutation takes place
    • 4- no migration
    • 5- no selection occurs
  11. definition for evolution
    • change through time
    • decent with modification
    • change in gene frequencies through time
  12. agents of evolutionary change
    • mutation
    • gene flow
    • nonrandom mating
    • genetic drift 
    • selection
  13. mutation
    • ultimate source of variation 1-10 times per 100,000 cell divisions
    • natural selection does not affect mutation rate
  14. gene flow
    • the movement of alleles from one population to another
    • low levels of gene flow homogenize allele frequencies among populations
  15. nonrandom mating
    certain genotypes are more likely to mate than others
  16. inbreeding
    • mating with relatives increases homozygosity
    • doesn't change allele frequency
  17. outcrossing
    • opposite of inbreeding increases proportion of heterozygosity
    • doesn't change allele frequency
  18. genetic drift
    • random changes by chance (most frequency in small populations)
    • leads to a loss of alleles in isolated populations
    • 2 types: founder effect; bottleneck effect
  19. selection
    • the result of differential fitness
    • artificial vs. natural
  20. 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
  21. allopatric speciation
    when populations are geographically separated
  22. sympatric speciation
    • when populations are together
    • much less common
  23. 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 polypoid species)
    • ex. Tragopogon (goat's beard)
  24. ecology
    the study of relationships among organisms and between organisms and their environment
  25. population
    a group of individuals from the same species that share the same habitat, share the same resources, and potentially interbreed
  26. demography
    the measurement and statistical study of characteristics of populations
  27. characteristics of populations
    • size
    • density
    • dispersion
    • age structure
    • sex ratio
    • natality and mortality
  28. size
    • total number of individuals
    • if population size is constant, then: b+i=d+e
    • b=births
    • i=immigration
    • d=deaths
    • e=emigration
  29. density
    number of individuals per unit area
  30. dispersion
    • how the individuals are spaced
    • 3 types: random, uniform, clumped
  31. age structure
    the relative number of individuals in each cohort
  32. natality
    birth rate
  33. TRV
    • each individual has a total reproductive value 
    • TRV= CRV+RRV where CRV is current reproductive value and RRV is residual reproductive value
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Bio Exam 3
2013-10-31 17:42:17

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