Sex and Behaviour 2.4 Flashcards
Parental investment is costly but increases what?
the probability of production and survival of young
what is classified based on the level of parental investment in offspring and number of offspring produced?
r-selected (r-strategists) and K-selected (K-strategists) organisms
where do r-selection tend to occur?
occurs in unstable environments where the species has not reached its reproductive capacity
where do K-selection tend to occur ?
stable environments
what are mating systems based on and what do these range from?
how many mates an individual has during one breeding season
these range from polygamy (polygyny and polyandry) to monogamy
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
many species exhibit sexual dimorphism as a product of what?
sexual selection
what type of sexual dimorphism occurs in some species?
Reversed sexual dimorphism
what does female choice involve?
females assessing honest signals of the fitness of males
what happens in lekking species?
males gather to display at a lek, where female choice occurs
what does success in male-male rivalry through conflict (real or ritualised) increase?
access to females for mating
what does sexual selection select for?
characteristics that have little survival benefit for the individual, but increase their chances of mating
what is the difference between egg and sperm?
sperm are produced in much larger quantity than eggs
an egg has a larger energy store
what does external fertilisation allow and what are the disadvantages?
- allows very large numbers of offspring to be produced
- many gametes are predated or not fertilised, no or limited parental care, leads to few offspring surviving
what does internal fertilisation allow and what are the disadvantages?
- allows increased chance of successful fertilisation and fewer eggs are needed.
Offspring can be retained internally for protection and/or development - higher offspring survival rate - energy is used in locating a mate and requires difficult direct transfer of gametes for one partner to another
what happens in polygyny?
one male mates exclusively with a group of females
what happens in polyandry?
one female mates with a number of males in the same breeding season
why do many species exhibit sexual dimorphism?
as a product of sexual selection
what happens in sexual dimorphism?
females are generally inconspicuous
males usually have more conspicuous markings, structures and behaviours
what happens in reversed sexual dimorphism?
females are more conspicuous than males
what are r-selected species?
they are:
- smaller
- have a shorter generation time
- mature more rapidly
- reproduce earlier in their lifetime (often only once)
- produce larger numbers of smaller offspring (which receive a smaller energy input)
- they give limited parental care so most offspring will not reach adulthood
what are k-selected species?
they are:
- larger
- live longer
- mature more slowly
- reproduce many times in the lifetime
- produce relatively few, larger offspring
- they give high level of parental care so many offspring have a high probability of surviving to adulthood
what can honest signals indicate?
- favourable alleles that increase the chances of survival of offspring (fitness)
- low parasite burden - suggests healthy individual
what happens in a monogamy mating system?
individuals have only one mate
what happens at a lek?
- dominant males occupy the centre of a lek, with subordinates and juveniles at the fringes as ‘satellite’ males
- female choice occurs during the display
