1.7 - Living with others: Mate choice and sociability

Question 1

Name a species where sexual fitness differs between sexes

Answer 1

elephant seals

Question 2

how does sexual fitness differ between male and female elephant seals? (3)

Answer 2

1. alpha males sire >90% of pups
2. Most males have none
3. most females have at least 1 pup

Question 3

describe sexual selection

Answer 3

when variance of reproductive success is greater in one/other sex sexual selection leads to secondary sexual characters

Question 4

when are sexually selected sex differences expected?

Answer 4

when sexual fitness limited by access to mates more than by access to resources

Question 5

what are the 2 mechanisms of sexual selection? (2)

Answer 5

1. intrasexual - male competition
2. intersexual - female choice

Question 6

what are the 2 reasons females prefer certain males? (2)

Answer 6

1. aesthetics - F preference evolves under natural selection, male signals evolve in response
2. information - F preferences evolve in response to male characteristics

Question 7

Give an example of females choosing a characteristic that resembles good genes

Answer 7

Peacocks
- eyespots correlate positively with offspring weight + survival

Question 8

give an example of females choosing a characteristic that resembles good behaviour

Answer 8

House finch
- positive correlation between feeding rates in males and plumage brightness (more red = better father)

Question 9

Describe why characters that reduce naturally selected fitness evolve (the handicap principle) (2)

Answer 9

1. costly trait (eg bright colouration) reduces survival
2. only healthy males can survive with handicap (handicap = healthy)

Question 10

why do females choose males with characters that naturally reduce fitness?

Answer 10

if advantage through superior genes outweighs cost of handicap net quality of females offspring will be enhanced

Question 11

What is assortative mating?

Answer 11

nonrandom mating pattern where individuals with similar phenotypes/genotypes are more likely to mate with each other than expected by chance

Question 12

what are the causes of assortative mating? (2)

Answer 12

1. optimal outbreeding - maintain genetic compatibility and heterozygosity
2. individual behavioural compatibility

Question 13

what are MHC molecules (2)

Answer 13

1. required immune system surveillance - resistance to pathogens
2. high allelic diversity in MHC genes - allows detection of many possible pathogens

Question 14

what molecule is involved in mate choice for many vertebrates via olfactory cues

Answer 14

MHC molecules

Question 15

why does parent-offspring conflict occur? (2)

Answer 15

1. natural selection maximises no. of reproductively successful offspring
2. offspring have less genetic interest in parents’/siblings’ future reproduction/ survival than own

Question 16

what can be an observed result of parent-offspring conflict?

Answer 16

siblicide in some birds

Question 17

what is it called when some individuals give up reproductive opportunities to help parent/siblings breed?

Answer 17

co-operativ breeding

Question 18

why do some species utilise co-operative breeding?

Answer 18

successful reproduction chances from members with no breeding experience much lower than those with experience + helpers

Question 19

Eusociality

Answer 19

the highest level of organisation of sociality

Question 20

What defines eusociality? (4)

Answer 20

1. adults live in groups
2. co-operative brood care
3. overlapping generations within colony
4. division of labour into reproductive/non-reproductive groups

Question 21

whats an example of eusociality in nature?

Answer 21

naked mole rats

Question 22

What % of surviving kits do dominant females account for?

Answer 22

80% - others normally act as helpers

Question 23

describe the role of meerkat sentinels (4)

Answer 23

1. non-breeder
2. looks out for predators
3. position rotates
4. sound alarm in response to predator sighting
   ( greatly benefits reproductive success)

Question 24

why do pregnant female meerkats kill others’ young? (2)

Answer 24

1. litters born half as likely to survive 4 days if subordinate female pregnant
2. dominant females more likely than subordinates to give birth when no ther females pregnant