2.4 Sex and Behaviour Flashcards
number of gametes produced by males
large
number of gametes produced by females
small
size of energy store in males gametes
small
size of energy store in female gametes
large
who invests the most when it comes to parental investment in most species
females
females invest in…
the egg structure in non-mammals or in the uterus during gestation in mammals
parental investment is
costly but increases the probability of production and survival of young
what can parental behaviour be classified into
r-selected species and k-selected species
what are r-selected species
smaller organisms that usually produce larger numbers of offspring, providing no parental care, having shorter life spans and have a lower offspring survival probability
what are k-selected species
larger organisms that usually produce lower numbers of offspring, providing more extensive parental care, have longer life spans and have a high offspring survival probability
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
in stable environments
what is internal fertilisation
the process by which the sperm and egg nuclei fuse inside the female
what is external fertilisation
the process by which teh sperm and egg nuclei fuse outside the female
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
benefits of external fertilisation
very large numbers of offspring can be produced
costs of external fertilisation
many gametes predated or not fertilised
no or limited parental care
few offspring survive
what are mating systems based on
how many mates an individual has during one breeding season
name the mating systems
monogamy
polygamy (polygyny and polyandry)
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
many animals have…
mate-selection courtship rituals
what are courtship rituals
a set of display behaviours in which an animal, usually a male, attempts to attract a mate
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 is sexual dimporphism
physical difference between males and females of a species
many species exhibit sexual dimorphism as
a product of sexual selection
what are females usually
inconspicuous
what are males usually
have more conspicuous markings, structures and behaviours
reversed sexual dimorphism occurs in…
some species such as vultures
what is female choice
involves females assessing honest signals of the fitness of males
what are honest signals
signals and behaviour in animals that are a true representation of their biological fitness
what can honest signals indicate
favourable alleles that increase the chances of survival of offspring (fitness) of a low parasite burden suggesting a healthy individual
what is lekking
during a lek males will display for females in a communal display area, then females will chose a mate
what happens in a lek
males gather to display, where female choice occurs
example of animal which exhibits lekking behaviour
birds
how are the animals ordered in a lek
dominant males occupy the centre of the lek, with subordinates and jubeniles at the fringes as ‘satellite’ males. during the display female choice occurs
what is a satellite male
male that sneaks to gain access to females
what is a sneaker
male that gains access to mate with females without the more dominant male knowing
what increases access to females for mating
success in male-male rivalry through conflict (real or ritualised)
what will males fight for
dominance and access to females, often using elaborate ‘weapons’ such as antlers, tusks, horns
