animal behavior.txt

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animal behavior.txt
2009-11-10 20:49:09
sex and sex ratio

lec 18
Show Answers:

  1. what are some cost of mating and meiosis?
    finding mate consumes time and energy and cost of meiosis is that recombination breaks up favorable gene complexes.
  2. what are some benefits of sex?
    • prevents muller ratchet
    • deleterious mutation accumulate in asexual lineages not sexual
    • providing long term benefits
    • creation of novel gene combination
    • red queen hypothesis : must constantly create new gene arrangement to combat pathogen evolution
    • providing short term benefits
  3. what are some types of sex determination?
    • genetic ( either chromosomal or genic)
    • environmental
    • social
  4. what is the mechanism of haplodiploidy?
    • haplodiploid males develop from unfertilized egg
    • diploid females develop from fertilized eggs
  5. what is social sex determination?
    • it depends on the mating system
    • many fish can undergo sex reversal
    • dominant female in sea bass changes into male when territorial male disappears.
  6. what is protogyny?
    starting life as female and then changing to male
  7. what is protandry?
    where male function precedes female function
  8. what is the null model for sex allocation?
    • parental strategies should evolve towars equal investment in offspring of the two sexes.
    • if sex ratio falls below 50% increased production of rare sex is favored
  9. what is the adaptive sex ratio bias?
    • maternal condition influences offspring investment ( trivers willard effect)
    • local mate competition
    • local resource competition
    • local resource enhancement
  10. what is trivers willard effect?
    • population sex ratio is 1:1, individual sex allocation depends on condition
    • if moms in good condition transfer competitive ability to sons more than daughter.
    • dominant individual sir more offspring
    • they produce more sons then daughters
    • female in poor condition should produce more daughters