5. Sex, Sexes, Hermaphroditism

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  1. What is the essence of sex?
  2. conjugation
    sex without reproduction

    when bacteria cells join to transfer genetic material via plasmid
  3. syngamy
    The fusion of gametes resulting in the formation of a zygote, which develops into a new organism with new combination of alleles
  4. cost of recombination
    breaks down a demonstrably fit genotype for a completely untested combination of alleles
  5. cost of meiosis
    sexual reproducers only contribute half of genes. Sex producers have to produce twice as much as asexual
  6. Cost of producing sons
    because males in sexual reproducers do not produce offspring. Therefore sons, genetically, are a waste.
  7. cost of mating
    time and energy, exposure to predators, disease
  8. The Adaptability Hypothesis
    • Fisher (1958) - sex increases diversity, and therefore increases the rate at which population can evolve and avoid extinction
    • does not explain how sex became popular. How sex became a thing when it is so costly.
  9. Muller's Rachet
    • mutation is usually harmful
    • Asexuals - any one mutation will be copied and copied and copied.
    • sexuals - those with serious mutations are less likely to reproduce and therefore edit out the mutation. 
    • the advantage of sex is fleeting. sex is costly.
  10. The Lottery Principle
    • G.C. Williams 1975
    • If offspring are likely to face an environment different from parents, it makes sense for parents to produce many diverse children. 
    • applies to r strategists who produce a lot but who do not invest in offspring.
    • does not apply to k strategists who produce few offspring and invest and have low mortality rate.
  11. Hamiltons Red Queen Hypothesis
    • the environment for k strategists is an equally moving target (all predators are adapting with time too)
    • best explains parasite resistance
    • sex changes game by producing a new unique genotype that parasites have never seen before
  12. Definition of male and female
    • male = small gametes
    • female = large gametes
  13. anisogamy
    • an = not
    • iso = same
    • gamy = gamete
    • differing gamete size
  14. disruptive selection
    when selection favors the extreme of a trait, not the mean (ex. gamete size)
  15. why doe sexes exist? 
    Parker, Baker, and Smith
    • multicellular organisms can't conjugate
    • large gametes = quality
    • small gametes = quantity
    • selection favors both, not a compromise. Therefore, sexes evolved.
  16. why do sexes exist?
    Cosmides and Tooby
    • sexes evolved to prevent the organelles of one parent from competing with the organelles of the other parent. 
    • intercellular competition would hurt zygote
    • therefore small gametes destroy their organelles, large gametes monopolize organelles, and zygote is safe.
  17. Offspring sex ratio
    • usually 50/50 across species
    • male fitness = generation size (G)/number of males (M)
    • female fitness = G/ number of females (F)
    • happy at G/M = G/F
    • selection will favor whichever sex is rare, except when one sex is too costly to produce.
  18. when does sequential hermaphrodites evolve?
    when size provides some kind of advantage
  19. when does protogyny evolve?
    when males need to be bigger to protect females or to compete for males
  20. when does protandry evolve?
    when it is more favorable that females produce large eggs
  21. when does simultaneous hermaphroditism evolve?
    when species is spread out and meeting another one of your species is rare. Low density
  22. why don't more species change sexes?
    the main reason why traits are obligate is that it would be too costly to change, even if there is an advantage to do so.
  23. what is r strategy
    lots of kids, not a lot of time
  24. k strategy
    few offspring, time and care into each
Card Set:
5. Sex, Sexes, Hermaphroditism
2015-02-23 20:17:52
Sex Sexes hermaphroditism
chapter 5 info
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