Evolutionary Biology Comp Exam.txt

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  1. Hardy-Weinberg equation
    • HWE states that allele and genotype frequencies in a population will remain constant from generation to generation as long as the following criteria is met:
    • 1. no mutations: no origin of new alleles
    • 2. No net Migration: no gene flow
    • 3. Genetic Drift: population must stay large in size
    • 4. Random mating: no preferential phenotypes for reproduction
    • 5. Selection: random survival of all phenotypes
  2. Formulas to calculate allelic frequencies if HWE criteria is met
    • p + q = 1
    • p^2 + 2pq + q^2 = 1
    • p = frequency of DOMINANT allele in pop
    • q = frequency of RECESSIVE allele in pop
    • p^2 = % of homozygous dominant individuals
    • q^2 = % of homozygous recessive individuals
    • 2pq = % of heterozygous individuals
  3. Pre-zygotic mechanisms with examples
    • 1. GEOgraphic isolation by vicariance (ancestral pop 1st, then barrier, followed by 2nd pop): Glaciation of Kamchatka peninsula in Russia separated polar bear from ancestral brown bear pop
    • 2. GEOgraphic isolation by dispersal (barrier 1st, then ancestral pop 2nd): Flies island-hopping across ocean BARRIERS allowed reproductive isolation among Hawaiin populations of Dros. to get new fly pops
    • 3. Temporal isolation (by hrs, days or seasons): In North America, eastern spotted skunks Breed in Spring, creating temporal barrier, which isolates them from western spotted skunks that Breed in the Fall
    • 4. Habitat isolation by sympatry (live in same area) or parapatry (live in different area with hybrid zone): Rhagoletic pomonella feeding on apples has diverged from ancestral populations feeding on Hawthorne fruits in North America
    • 5. Behavioral or pollinator isolation: White-eyed Dros have LOWER mating success vs red-eyed
    • 6. Mechanical isolation (structural incompatibility): Different dragonfly species cannot mate due to the four wings not fitting properly
    • 7. Gamete isolation (inviable, or unrec): Male gametes from one deer species cannot survive in reproductive tract of other deer species
  4. Post-zygotic mechanisms with examples
    • 1. Ecologic F1 inferiority (extrinsic barrier): Anthoxanthum odoratum (grass) hybrids become metal TOLERANT and sensitive, making them NOT fit enough for one type of soil, so parents out compete them.
    • 2. Behavioral F1 inferiority (extrinsic barrier): Canis Lupus (grey wolf) crossed with western coyote yield F1 hybrids (northeastern coyote) with LOW mating success
    • 3. F2 hybrid breakdown (INtrinsic barrier): Gossypium barbadense (Egyptian cotton plants) crossed with G. hirsutum (Caribbean cotton plants) yield F1 hybrids which are fertile, but when crosed the F2 hybrids are INVIABLE (sick, weak, low fertility)
    • 4. F1 hybrid sterility (INtrinsic barrier): Equus caballus mares (females horses) mating with Equus asinus stallions (male donkeys) yield F1 hybrid mules that are usually STERILE (males always, sometimes females are not)
    • 5. F1 hybrid Sterility Inviability (intrinsic barrier): Copper tolerant populations of Yellow monkey flowers when crossed with copper Sensitive populations mostly produced INVIABLE F1 hybrids based on mutant allele for copper tolerance coming from a copper sensitive population arisen ~100 years ago in Cali.
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Evolutionary Biology Comp Exam.txt
Evolutionary Biology Comp Exam
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