AH Bio 2.4

why do females invest more than males during sexual reproduction?

egg structure in non-mammals and gestation in mammals

what dies parental investment increase the probability of?

production and survival of young

what are the characteristics of an r-selected species?

- smaller
- shorter generation time
- fewer breeding occasions
- many offspring
- limited parental care
- low offspring survival rate

what are the characteristics of a k-selected species?

- larger
- longer generation time
- many breeding occasions
- fewer offspring
- extensive parental care
- higher offspring survival rate

what kind of environment does r-selection tend to occur?

unstable

in external fertilisation, where do the eggs and sperm meet?

watery habitats outside the body

in internal fertilisation, where do the eggs and sperm meet?

within the body of female individuals

what is a principle benefit of external fertilisation?

large numbers of offspring can be produced at one time

what are the costs of external fertilisation?

many gametes could be predated or not used in fertiisation

what is a main benefit of internal fertilisation?

fewer eggs are needed because of an increased chance of successful fertilisation

what are the 2 costs of internal fertilisation?

- the need to locate a mate of the opposite sex
- the difficulty of the direct transfer of gametes from one partner to the other

what are mating systems based on?

how many mates an individual has during one breeding season

what is polygamy?

when individuals of one sex have more than one mate

what is polygyny?

when one male mates exclusively with a group of females

what is polyandry?

when one female mates with a number of males during one breeding season

what is monogamy?

the mating of a pair of animals to the exclusion of all others

what is courtship behaviour?

behaviour that leads to breeding success

what can courtship behaviour in birds and fish be a result of?

species specific sign stimuli and instinctive fixed action pattern responses

what does sexual selection select for?

characteristics that have little survival benefit for the individual but increases their chance of mating

what do many species exhibit as a result of sexual selection?

sexual dimorphism

what is sexual dimorphism?

females are generally inconspicuous while males usually have more conspicuous markings , structures and behaviours

what does female choice involve?

females assessing honest signals of the fitness of males

what can honest signals indicate?

favourable alleles that increase the chances of survival of offspring or a low parasite burden suggesting a healthy individual

what happens in lekking species?

males gather to display at a lek, where female choice occurs

in bird species, what is the formation of a lek?

dominant males occupy the centre of the lek, with subordinates and juveniles at the fringes as ‘satellite’ males

what does success in male-male rivalry through conflict increase?

access to females for mating

what do males often use during male-male rivalry?

elaborate ‘weapons’ such as tusks, antlers and horns