Sexual selection Flashcards
1
Q
What was Darwin’s problem with peacocks?
A
- The peacock’s tail
- Increases risk of predation so must have a benefit
- Sexual selection
2
Q
What selection is male-male competition?
A
- Intrasexual selection
- Competition between members of the same sex
3
Q
What selection is female choice?
A
- Intersexual selection
- Choice (by one sex) of mates of the other sex
4
Q
What are secondary sexual characters?
A
- Size
- Fighting ability
- Weapons
- Body colouration etc
5
Q
What is the underlying basis for sexual selection?
A
- Male and female gamete size difference
- Anisogamy
- Sexual selection works differently on the sexes
6
Q
Male-male competition examples: Elephant seals
A
- Male elephant seals - dominant beachmasters have higher mating success - selection pressures to grow large.
7
Q
Male-male competition examples: Common toad
A
- Weight / large size of male has more advantages because they can displace smaller males and mate with female.
8
Q
Body size and Harem size in pinnipeds: How does males / female size relate to harem size?
A
- In monogomous species, Male / female body size do not differ
- Body size dimporphism increases as harem size increases - sexual dimorphism
9
Q
Antler length and mating system in deer
A
Polygnous males have longer antlers than monogamous males
10
Q
Sexual selection doesnt have to lead to sexual dimorphism: Example?
A
Crested auklets
11
Q
How can natural selection lead to sexual dimorphism?
A
- Sexual dimorphism can arise if the sexes occupy different niches
- E.g. Huias birds with differing bill morphologies
12
Q
Female choice example
A
- Widow bird (long tails)
- Females preferred long tailed males
- Female choice has lead to runaway selection
13
Q
Choice in great crested auklets: Mutual sexual selection
A
- Long crest length increased courtship
- Both males and females performed more courtship behaviours to long crested models (of the opposite sex).
- Male-male interactions are won by long crested birds
- Female-female interactions are won by long crested females
- Both sexes perform courtship displays
14
Q
Example of Sex role reversal
A
- Pipefish: males get pregnant
- Males are the limiting sex
- Female bias
- Males choose females that are large and produce more eggs
15
Q
Sex role reversal: Mormon Crickets
A
- Produce a edible spermatophore that is 25% of their body weight
- Can only produce once in life
- Females have greater reproductive output
- Males are choosy
