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Evolution > Sexual Selection I and II > Flashcards

Sexual Selection I and II Flashcards

1
Q

define sexual dimorphism

A
  • when opposite sexes differ
  • example: different morphologies
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2
Q

when can you explain sexual dimorphism via natural selection

A
  • when the trait/dimorphism is directly linked to the ability to survive in their environment
  • other times its explained by sexual selection
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3
Q

define sexual selection

A

differential reproductive success due to variation in success at getting mates

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4
Q

natural vs sexual selection

A
  • natural selection: focus on survival related traits
  • sexual selection: focused on sexual related traits
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5
Q

natural vs sexual selection: which is directional, stabilizing, or disruptive?

A
  • both can be all since they are context dependent
  • if opposed, often results in stabilizing selection (common but not always the case)
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6
Q

how can sexual selection has been expanded to explain differences between males and females

A
  • typical female: invest more in gametes bc eggs are more expensive
  • typical male: really low investment in gametes bc sperm is less expensive
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7
Q

define female and male

A
  • female: ability to produce eggs
  • male: ability to produce sperm
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8
Q

define egg and sperm

A
  • egg: larger gamete
  • sperm: smaller gamete
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9
Q

what kind of selection led to having two sexes?

A

disruptive

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10
Q

explain how disruptive selection resulted in 2 sexes

A
  • started with isogamy (gametes are all the same size) with their own variation
  • accumulation of mutations then cause anisogamy (different sizes)
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11
Q

what produces asymmetric limits on reproductive success

A

differences in reproductive investment

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12
Q

explain the asymmetric limits on reproductive success - females

A

reproductive success will be limited by the number of eggs she can make

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13
Q

explain the asymmetric limits on reproductive success - male

A

reproductive success will be limited by the number of females he can mate with

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14
Q

which sex should have the greatest variation in reproductive success among individuals?

A

males since their success is determined by another individual

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15
Q

asymmetric limits on reproductive success - explain Bateman and Trivers (1948) prediction

A
  • they predicted that sexual selection should be stronger on males than on females
  • this is bc males have stronger variation and thus stronger selection
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16
Q

define hermaphrodites

A
  • simultaneously having both male and female organs
  • Protandrous (male -> female)
  • Protogynous (female -> male)
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17
Q

Bateman and Trivers (1948) prediction - explain the Bateman’s gradient

A
  • statistical relationship that measures how reproductive success is related to mating success
  • has both male and female data
  • x-axis: number of mates
  • y-axis: number of offspring
  • slope: fitness
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18
Q

Bateman gradient: hermaphrodite snail study - explain how sexual selection is stronger on sperm producers

A
  • males: linear increase in fitness and more variation
  • females: very little advantage with each additional mating and not a lot of variation
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19
Q

Bateman gradient - rough-skinned newts example

A
  • researchers captured newts from breeding pond
  • females were kept captive and induced to lay eggs
  • used genetic techniques to assign reproductive success to males
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20
Q

Bateman gradient: rough-skinned newts example - describe gradient results

A
  • males: not all males mate but slope increases linearly
  • females: all females mate but slope is a lot flatter (not a lot of variation)
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21
Q

Bateman (1948) fruit fly experiment

A
  • tested intra-sexual selection in Drosophila
  • said males will be risker with mates since they don’t have limits on their gametes, unlike females
  • tried to apply this to humans but this assumption is wrong
22
Q

Bateman (1948) fruit fly experiment - why was this assumption wrong

A
  • assumed that the optimal strategy for males for all species will be to mate with as many females as possible
  • and that the optimal strategy for females would be to choose one male and mate with him only
23
Q

Bateman (1948) assumption - example of how its wrong

A
  • sex role reversal species
  • in some species, males provide parental care
  • Bateman gradient is flipped: females have more variation and males have less
24
Q

explain Bateman’s view on selection between sexes

A
  • males: more mating = more offspring = more fitness
  • females: better genes/rearing = healthier offspring = more fitness
25
Q

selection between sexes - how can we reframe Bateman’s view

A
  • instead of males: members of the sex subject to strong sexual selection will be competitive
  • instead of females: members of the sex subject to weak sexual selection will by choosy
26
Q

define intersexual selection

A

between sexes (male and female)

27
Q

define intersexual selection

A
  • between individuals (male and male)
  • same-sex compeition
28
Q

intrasexual selection - what does it drive the evolution of

A
  • size dimorphism (competing sex is larger)
  • stamina (competing sec has more)
  • weaponry
29
Q

intrasexual selection: what is most common in sexual dimorphism

A
  • more colorful male birds and bigger male mammals
  • birds: intersexual selection
  • mammals: intrasexual selection
30
Q

intrasexual selection: iguana example - can natural selection explain sexual dimorphism

A
  • no
  • a lot of males are bigger than the optimum
31
Q

intrasexual selection: iguana example - what might explain the fact that many of the males are larger than the “optimum size”?

A

sexual selection

32
Q

intrasexual selection: iguana example - what traits does it favor and what kind of selection is present

A
  • large body size
  • stabilizing
33
Q

intrasexual selection: iguana example - how is sexual selection favoring large body size

A
  • males establish territories on areas where females bask
  • males fight to maintain territories (bigger size = more fights won)
  • ability to hold territory through combat matches fitness and reproductive sucess
34
Q

intrasexual selection: iguana example - what happens due to a skew in fitness among males?

A
  • alternative mating tactics
  • males with no territories will try anything to get some fitness (some is better than none)
35
Q

intrasexual selection: iguana example - what are the alternative mating tactics

A
  • territorial
  • non-territorial satellite
  • female mimic sneaker
36
Q

intrasexual selection: alternative mating tactics - what are satellite males

A

they ejaculate early so that some sperm will make it into the female even if population is interrupted by the territorial male

37
Q

intrasexual selection: alternative mating tactics - sneakers

A

involves a male sneaking up on a female to fertilize her without directly competing with dominant males

38
Q

non-combative intrasexual male competition

A
  • post-copulatory (sperm) competition
  • alternative mating tactics
  • female manipulation through mate guarding
  • copulatory plugs
  • infanticide
39
Q

post-copulatory (sperm) competition - amount

A
  • sperm production increase
  • ex: Medflies produce more sperm when raised with rivals vs in isolation
39
Q

non-combative intrasexual male competition - post-copulatory (sperm) competition

A

can select for:
- amount
- sperm attributes
- mechanism
- removal

40
Q

post-copulatory (sperm) competition - sperm attributes

A
  • higher sperm velocity
  • ex: guppies
41
Q

post-copulatory (sperm) competition - mechanism

A
  • order of matting effects which male’s offspring is which
  • the last gets most offspring
  • ex: guppies
42
Q

post-copulatory (sperm) competition - removal

A
  • males evolved scooping out sperm of previous mating
  • ex: dragonflies
43
Q

what is sexual conflict

A

two sexes have conflicting optimal fitness strategies concerning reproduction

44
Q

post-copulatory (sperm) competition: mechanism - is there a possibility for sexual conflict?

A
  • yes, genital arms race
  • ex: complexity and elaboration of Muscovy duck penises
45
Q

post-copulatory (sperm) competition: mechanism and sexual conflict - genital arms race

A
  • forced copulation results in females evolving internal control (vaginal shape)
  • then male evolves to circumvent control resulting in females evolving new control
  • keeps going and going
46
Q

post-copulatory (sperm) competition: removal - is there a possibility for sexual conflict

A
  • yes
  • ex: dragonfly females play dead to avoid copulation with unwanted male
47
Q

non-combative intrasexual male competition - mate guarding

A
  • after mating, the sperm producer guards the egg producer to make sure all the eggs are fertilized
  • potential for sexual conflict
48
Q

non-combative intrasexual male competition - copulatory plug

A
  • male plugs female reproductive tract to prevent mating
  • potential for sexual conflict
49
Q

non-combative intrasexual male competition - infanticide

A
  • this is adaptive bc individual is killing unrelated offspring
  • potential for sexual conflict: yes - females band together to fight males

Evolution (13 decks)

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