Organisms and Evolution - Sex and Behaviour Flashcards
Which gender has the greatest parental investment?
Females
Why is parental investment so great in some animals even although it is costly?
It increases the probability of production and survival of
young
How are r-selected and k-selected organisms classified?
Based on level of parental investment in offspring and number of offspring produced
What are the characteristics of r-selected species?
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 only a smaller energy input; Limited parental care; Most offspring will not reach adulthood
What are the characteristics of k-selected species?
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
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 are the benefits of external fertilisation?
Very large numbers of offspring can be produced
What are the costs of external fertilisation?
Many gametes predated or not fertilised;
No or limited parental care;
Few offspring survive
What are the 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
What are the 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
What are the mating systems?
Polygamy - Polygyny
- Polyandry
Monogamy
Define polygamy?
Individuals of one sex have more than one mate
Define polygyny?
One male mates exclusively with a group of females
Define polyandry?
One female mates with a number of males in the same breeding season
Define monogamy?
The mating of a pair of animals to the exclusion of all others
What can successful courtship behaviour in birds and
fish be a result of?
Species-specific sign stimuli and fixed action pattern responses
Describe sexual selection
Sexual selection selects for characteristics that have little survival benefit for the individual, but increase their chances of mating
What do many species exhibit as a product of sexual selection?
Sexual dimorphism
Describe males and females involving sexual dimorphism?
Females are generally inconspicuous; males usually have more conspicuous markings, structures and behaviours
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 do honest signals indicate?
Favourable alleles that increase the chances of survival of offspring (fitness) or a low parasite burden suggesting a healthy individual
What happens in lekking species?
Males gather to display at a lek, where female choice occurs
What are the details of lekking?
Some bird species exhibit lekking behaviour.
Dominant males occupy the centre of the lek, with subordinates and juveniles at the fringes as ‘satellite’ males. During the display,
Female choice occurs
Success in male-male rivalry through conflict (real or ritualised), increases access to what?
Females for mating
What happens with male-male rivalry?
Males will fight for dominance and access to females, often using elaborate ‘weapons’ such as antlers, tusks, horns.
