2.4 Sex and behaviour

What are female gametes in relation to number and energy store

Large, expensive to produce, limited in number and produced infrequently. If fertilised this will lead to high costs to the female

What are male gametes in relation to number and energy store

Small, have no nutrients, cheap to produce, constantly made throughout life. Produced in large numbers

What is the cost and benefit of parental investment

Costly but increases the probability of production and survival of young

What are the characteristics of r-selected species

smaller; have a shorter generation time; mature more rapidly; reproduce earlier in their lifetime, often only once; produce a larger number of smaller offspring, each of which receives only a smaller energy input; limited parental care; most offspring will not reach adulthood

What are the characteristics of k-selected species

larger and live longer; mature more slowly; can reproduce many times in their lifetime; produce relatively few, larger offspring; high level of parental care; many offspring have a high probability of surviving to adulthood

Where does r-selection tend to occur

In unstable environments where the species has not reached its reproductive capacity

Where does K-selection tend to occur

stable environments

What are the benefits of external fertilisation

very large numbers of offspring can be produced

What are the costs of external fertilisation

many gametes predated or not fertilised; no or limited parental care; few offspring survive

What are the benefits of internal fertilisation

increased chance of successful fertilisation; fewer eggs needed; offspring can be retained internally for protection and/or development; higher offspring survival rate

What are the costs of internal fertilisation

a mate must be located, which requires energy expenditure; requires direct transfer of gametes from one partner to another

What are mating systems based off of

How many mates an individual has during one breeding season

Ranging from monogamy to polygamy

What is monogamy

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

What is polygamy

individuals of one sex have more than one mate

What is polygyny

One male mates exclusively with a group of females

What is polyandry

one female mates with a number of males in the same breeding season

What do many animals have

Mate-selection courtship rituals

What can successful courtship behaviour in birds and fish be a result of

species-specific sign stimuli and fixed action pattern responses

What does sexual selection select

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

What do many species exhibit as a product of sexual selection

sexual dimorphism

What are females generally

inconspicuous

What are males generally

Usually have more conspicuous markings, structures and behaviours

What occurs in some species

reversed sexual dimorphism

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 (fitness) 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

What do some birds species exhibit

Lekking behaviour

what is the format of the lekking behaviour

Dominant males occupy the centre of the lek, with subordinates and juveniles at the fringes as 'satellite' males. During the display female choice occurs

What does success in male-male rivalry through conflict (real or ritualised) increase

assess to females for mating

What will males fight for

dominance and access to females

How will males fight for females

using elaborate 'weapons' such as antlers, tusks, horns

why do marine animals use external fertilisation

water allows sperm to reach eggs