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APS 209: Animal behaviour > 6: Sexual selection > Flashcards

6: Sexual selection Flashcards

1
Q

what is Darwin’s theory of NS? (2)

A
  • the fittest individuals will survive and reproduce

- succeeding generations will become adapted to their environment

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2
Q

what is the problem with NS, also known as the peacocks tail?

A

it cant explain costly traits that lower an individual’s survival

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3
Q

what is SS and what are the 2 main types?

A

a struggle between the individuals of one sex, usually males, for possession of the other sex, resulting in differential reproductive success

  • male male competition (intrasexual) same sex
  • female choice (inter) one sex chooses mate of another sex
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4
Q

what are secondary sexual characters?

A

distinguishes between the sexes but is not directly linked to reproduction
- size, colouration , courtship displays

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5
Q

give 3 examples of secondary sexual characters

A
  • salmon: males have hooked jaw and red colouration in spawning season
  • moose: antlers for display
  • wilson’s bird of paradise: bright plumage
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6
Q

what is the basis for SS, causing it to arise?

A

Anisogamy

allows SS to act differently on the 2 sexes

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7
Q

what is anisogamy?

A

different sized gametes

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8
Q

what can it lead to if the male competes and the female chooses?

A

sexual dimorphism

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9
Q

what did Bateman 1948 discover about the potential reproductive rate in Drosophila? (5)

A
  • after first copulation little change in number of offspring produced by females
  • male reproductive success increased linearly with copulations
  • males have higher potential reproductive rate than females
  • female success limited by number of eggs can produce
  • leads to female choosing the best male
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10
Q

what is the sexual dimorphism in mallard ducks?

A

females plain and males have bright plumage

males show courtship behaviour

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11
Q

what is the most basic form of male-male competition?

A

direct physical contests among members of one sex over access to mates

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12
Q

what did Le Boeuf 1974 fins when studying elephant seals in California? (5)

A
  • males can weigh 2000kg
  • fight vigorously
  • winner/beachmaster has harem of dozens of females
  • other males get few/no mating
  • males compete for harems with violent fights
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13
Q

what did McCann discover when studying competition and dominance in elephant seals on south Georgia? (5)

A
  • males fight to become dominant
  • dominance correlated with mating success
  • higher dominance rank = more copulations
  • DNA analysis shows mating success linked to paternity
  • location important as large males selected for on the beach but smaller males when in the sea as can sneak up on females
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14
Q

what did Davies and Halliday 1978 discover about male-male competition in Bufo bufo toads that grab passing females to mate with them? (5)

A
  • 10/23 small males were displaced by a larger male
  • 13/23 small males successfully mated with female
  • 18/18 large males successfully mated
  • evolutionary pressure on males to get larger to increase reproductive success
  • but no pressure on females so is sexual size dimorphism
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15
Q

what is the relationship between body size and harem size in pinnipeds?

A

as body size dimorphism increases harem size increases

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16
Q

where is there more male-male competition and more sexual dimorphism, using pinnipeds as an example?

A

mono systems- little male-male competition

poly- more sexual dimorphism

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17
Q

what was discovered for anter length as a weapon in deer mating systems?

A
  • polygynous males have larger and longer antlers than would expect for body size
  • mono has smaller than would expect
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18
Q

what does SS NOT have to lead to and how else can it arise?

A

sexual dimorphism

can arise from processes other than SS

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19
Q

give an example of how sexual dimorphism can arise from a process other than SS

A

Huias birds

  • males have shorter bills compared to long probing beaks of females
  • both occupying 2 different niches
  • reduces food competition between the partners
20
Q

what is female choice hard to distinguish from and how can we show female choice with certainty?

A

male-male competition

carry out experimental manipulations

21
Q

what is the Widowbird example by Andersson 1982 to determine if female choice is the underlying mechanism? (5)

A
  • 4 groups of test males: 1 group tail elongated, 1 cut short, 1 left alone, 1 tail cut and restuck
  • males with long tails tended to mate with more females than those with short
  • females with long tails prefer males with long tails
  • female choice
  • female female competition may occur
22
Q

what is the general outcome for each of these:

a) low investment in offspring
b) high investment in offspring
c) equal investment

A

a) competition
b) choice
c) both sexes compete and both sexes choose- mutual and often monogamous

23
Q

give 3 points about crested auklets that were studied by Jones and Hunter 1993?
- what was compared?

A
  • both sexes invest in the offspring
  • both sexes have crests
  • evolved by sensory exploitation
  • compared attractiveness of models with short crests to those with long
24
Q

what were the results on the study of crested auklets by Jones and Hunter 1993? (2)

A
  • M + F performed more courtship displays to long crested males which indicates mutual mate choice
  • in both sexes ling crested individuals are dominant which indicates mutual competition
25
Q

in the study by Jones and Hunter 1993 what % of these interactions were won by long crested birds: male-male and female-female?

A

M-M: 86%

F-F: 83%

26
Q

what is the general observation and prediction with sex role reversal?

A
  • observe: in some species males invest more into reproduction than females
  • predict: more sex role reversal in these species with the female competing and the male being choosy
27
Q

give 7 points about the sex role reversal in pipefish

A
  • males get pregnant
  • males provide O2 and nutrients to egg clutches in an egg pouch
  • females can produce eggs to fill 2 male pouches
  • females larger and more competitive
  • even sex ratio so pouch space limited
  • males choose larger females that produce more eggs
  • female biased operational sex ratio
28
Q

what 2 things may be provided by males often in sex role reversal?

A
  • nutritious spermatophores

- nuptial gifts such as in cricket pairs where the female feeds as the male copulates

29
Q

give 3 important points about SS

A
  • any pattern of choice and competition can occur
  • each sex can play both roles
  • the environment can influence the pattern of SS
30
Q

what is another name for Australian Katydids?

A

Kawanaphila

31
Q

what was found in a study on sex role reversal in katydids given that food supply varies greatly through the breeding season? (3)

A
  • when pollen food limited spermatophores hard to produce so produced slower, males are choosy in mating and the females compete more
  • when food is abundant males are not choosy
  • M + F change behaviour based on environment
32
Q

what are mormon crickets and what noise do males make?

A

large, flightless orthoptera

chirping

33
Q

what do male mormon crickets transfer?

A

huge edible spermatophore, 25% its body mass, to females so only mate once

34
Q

how does female investment compare to males in mormon crickets? (4)

A
  • females put fewer resource into mating
  • female biased operational sex ratio
  • females compete for males
  • male choosy and prefers heavier females that can produce more eggs
35
Q

for mormon crickets what forms in areas where females compete and males are choosy?

A

high density mating aggregations

36
Q

what does SS and NS favour?

- which is faster?

A

SS: mate acquisition and fertilisation
NS: survival and fecundity
- SS as focused on 1 gen

37
Q

what are the 4 ecological interactions with SS?

A
  • food resources
  • predation
  • parasitism
  • sensory bias
38
Q

what is a cost to sexual ornaments?

A

mortality

39
Q

what can explain traits that go against NS?

A

SS

40
Q

give 3 examples of direct benefits from mate choice

A
  • fertile or fecund mates
  • good parenting ability
  • resources
41
Q

what often makes an individual compatible as a mate?

A

complementary and dissimilar MHCs

42
Q

what does male-male competition often lead to?

A

sexual dimorphism

43
Q

what is an example of a case where a group of males will cooperate?

A

low ranking baboon males work together to gain copulations with females guarded by dominant males

44
Q

what is an example of where a male and a female is cooperating?

A

female insect releases sex pheromone that males are attracted to

45
Q

how do female crickets mating promiscuously with non siblings as well as siblings benefit according to Wedell?

A

higher hatching success and avoids low egg viability

APS 209: Animal behaviour (25 decks)

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