UNIT 2 - sexual differences Flashcards
what is one key difference between sperm and egg cells?
Sperm are produced in much larger numbers than eggs but each egg has a larger energy store
what is parental investment and what is one cost and one benefit of it?
any parental expenditure that benefits offspring; it increases the offspring’s chances of surviving and reproductive success at the expense of the parent’s ability to invest in other offspring.
what are the qualities of R selected species?
r-selected species are:
- 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 a smaller energy input.
- They give limited parental care so most offspring will not reach adulthood.
what are the qualities of K-selected species?
K -selected species are:
- larger
- live longer
- mature more slowly
- can reproduce many times in their lifetime
- produce relatively few, larger offspring.
- They give a high level of parental care so many offspring have a high probability of surviving to adulthood.
where do R selection and K selection occur?
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
what are the pros and cons of external fertilisation?
Using external fertilisation allows very large numbers of offspring to be produced, but many gametes are predated or not fertilised, and there is no or limited parental care; few offspring survive.
what are the pros and cons of internal fertilisation?
Using internal fertilisation increases the chance of successful fertilisation and fewer eggs are needed. Offspring can be retained internally for protection and/or development, and there is a higher offspring survival rate. In internal fertilisation, energy is used in locating a mate and it requires the difficult direct transfer of gametes from one partner to another.
what are mating systems?
Mating systems are based on how many mates an individual has during one breeding season and range from polygamy to monogamy in which individuals have only one mate.
what is polygyny?
In polygyny, one male mates exclusively with a group of females. usually, the dominant male has the right to mate exclusively.
how do some species signal interest in others of the same species?
Many animals have mate-selection courtship rituals, often involving species-specific sign stimuli and fixed action pattern responses in some birds and fish.
what are fixed action patterns?
Fixed action patterns are specie-specific sequence of behaviour in which one behaviour leads to the next
how does sexual selection work?
§Sexual selection selects for characteristics that have little survival benefit for the individual, but increase their chances of mating.
what do some organisms exhibit as a result of sexual selection?
Many species exhibit sexual dimorphism as a product of sexual selection in which females are generally inconspicuous and males usually have more conspicuous markings, structures and behaviours.
what is female choice?
Female choice involves females assessing the fitness of males.
what are honest signals?
Honest signals are characteristics that can indicate fitness/favourable alleles or a low parasite burden, suggesting a healthy individual.
what is a lek?
a communal area in which two or more males of a lekking species perform courtship displays called lekking
what is male-male rivalry?
males will fight for dominance and access to females for mating through real or ritualised conflict
monogamy meaning?
the mating of a pair of animals to the exclusion of all others
what does polygamy mean?
Polygamy - individuals of one sex having more than one mate
polygyny meaning?
Polygyny - one male mates with a number of females in the same breeding season
polyandry meaning?
Polyandry - one female mates with a number of males in the same breeding season
sexual dimorphism meaning?
the differences in appearance between males and females of the same species, such-as in colour, shape, size and structure, as a product of sexual selection
what is a species specific sign stimulus?
a feature or action that indicates intent, often to start courtship
what is sexual selection?
selection for characteristics that have little survival benefit for the individual, but increase their chances of mating
what is reversed sexual dimorphism?
Reversed sexual dimorphism occurs in some species in which females are more conspicuous than males.
what is the key benefit of polygyny?
dominant male passes on lots of copies of his ‘fit’ alleles.
