4 - sex and behaviour Flashcards
Compare sperm and egg production in relation to number and energy store; greater investment by females.
females produce 400,00 follicles and release only a few hundred eggs though her lifetime. in males each ejaculate may contain 50-130 million sperm.
Sperm cells are much smaller than eggs so sperm are biologically less costly to produce. Also when females reproduce they then have to bear the entire nutritional burden of nurturing the offspring until it has hatched/is born.
Describe how organisms are classified as r-strategists or K-strategists.
Species that are suited to their life history to maintain a stable population with low fluctuations are called K-selected.
Species that are suited to their life history due to rapid population growth are called r-selected.
state
R-selection tends to occur in unstable environments where the species has not reached its reproductive capacity, whereas K-selection tends to occur in stable environments.
Compare the costs and benefits of external and internal fertilisation
External fertilisation advantages; a very large number of offspring can be produced because the females and males release such a large quantity of eggs and sperm, many eggs are fertilised. Disadvantages ; many gametes are predated or not fertilised and no or limited parental care meaning few offspring survive.
Internal fertilisation advantages; high chance offspring will survive therefore fewer eggs need to be produced conserving energy and gametes neet in a small space, increasing the chance of successful fertilisation. Disadvantages; a mate must be located, which requires energy expenditure and requires directs transfer of gametes from one partner to another.
state
Mating systems are based on how many mates an individual has during one breeding season.
Describe the terms polygamy (polygyny and polyandry) and monogamy.
Monogamy = the mating of a pair of animals to the exclusion of all others.
Polygamy = 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.
state
Many animals have mate-selection courtship rituals
Describe the role of species-specific sign stimuli and fixed action pattern responses in birds and fish.
The sign stimulus is usually a highly specific signal that is consistently encountered at an appropriate time. Fixed action pattern is a sequence of coordinated movements that are performed together as a “unit” without interruption.
state
Sexual selection selects for characteristics that have little survival benefit for the individual, but increase their chances of mating
Describe sexual dimorphism and reversed sexual dimorphism.
Sexual dimorphism is when females are generally inconspicuous and males have more conspicuous markings, structures and behaviours.
Reversed sexual dimorphism is when the female is larger than the male.
Describe the process of female choice and the use of honest signals
Female choice involves females assessing honest signals of the fitness of males. Honest signals can indicate favourable alleles that increase the chances of survival of offspring (fitness) or a low parasite burden suggesting a healthy individual.
Describe the reproductive strategy of lekking species
A lek is an aggregation of males that gather to engage in competitive displays that may entice visiting females into mating.
Describe male-male rivalry
Success in male-male rivalry throughout conflict (real or ritualised), increases access to females for mating. Males will fight for dominance and access to females, often using elaborate ‘weapons’ such as antlers, tusks and horns.
