Sex and Bevaviour Flashcards
What type of gametes has a greater number?
Sperm
What type of gamete has a smaller energy store?
Sperm.
What do females invest in?
Egg structure in non mammals or in the uterus and during gestation in mammals.
Parental investment?
Costly but increases probability of production and survival of young.
R selected species classification?
- smaller
- shorter generation time
- mature more rapidly
- reproduce earlier in their lifetime (often only once)
- produce a larger amount of smaller offspring, each receives only a small energy input.
- Limited parental care
- most offspring will not reach adulthood
K selected species classification?
- 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
When does R selection tend to occur?
In unstable environments where the species has not reached its reproductive capacity.
When does K selection tend to occur?
In stable environments.
Benefits of external fertilisation?
Very large number of offspring can be produced
Costs of external fertilisation?
- Many gametes predated and not fertilised
- no or limited parental care
- few offspring survive
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
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 on?
How many mates an individual has during one breeding season.
Monogamy?
Mating of a pair of animals to the exclusion of all others.
Polygamy (polygyny and polyandry)
Individuals of one sex have more than one mate.
Polygyny?
One male mates exclusively with a group of females.
Polyandry?
One female mates with a number of males in the same breeding season.
Mate selection courtship rituals?
Successful courtship behaviour in birds and fish can be a result of species-specific sign stimuli and fixed action pattern responses.
What does sexual selection select for?
Characteristics that have little survival benefit for the individual, but increase their chances of mating.
What do many species exhibit as a result of sexual selection?
Sexual dimorphism
Females are generally ———-
Inconspicuous
Males usually have ———
More conspicuous markings, structures and behaviours.
What does female choice involve?
Females assessing honest signals of the fitness of males.
What are honest signals?
They indicate favourable alleles that increase their chances of survival of offspring (fitness) or a low parasite burden suggesting a healthy individual.
