Sex and Behaviour Flashcards
Compare sperm and egg production
Sperm - Smaller than egg, always far more numerous than eggs
Egg - Larger than sperm due to the need to have an energy store for the developing embryo, eggs are fewer in number.
Which gender shows greater parental investment ?
-Greater investment by females
-Female investment in the egg structure in non-mammals or in the uterus and during gestation in mammals.
-Parental investment is costly but increases the probability of production and survival of young
Also, humans (mammals): Prolonged internal gestation, placentation, lactation
How are organisms classified ?
R-selected (r-strategists) or K-selected (K-strategists) organisms based on level of parental investment in offspring and number of offspring produced
What are characteristics of an r-selected species?
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 characteristics of K-selected species?
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
When do r and K selection tend to 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 costs and benefits of external fertilisation ?
External fertilisation
Benefits:
-Very large numbers of offspring can be produced
Costs:
-Many gametes predated or not fertilised
-No or limited parental care
-Few offspring survive
What are the costs and benefits of internal fertilisation ?
Internal fertilisation
Benefits:
-Increased chance of successful fertilisation
-Fewer eggs needed
-Offspring can be retained internally for protection and/or development
-Higher offspring survival rate
Costs:
-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 ?
-Mating systems are based on how many mates an individual has during one breeding season
-These range from polygamy (polygyny and polyandry) to monogamy
Mating systems are used by animals to ensure as many, healthy offspring are produced each breeding season, to ensure the survival of the species.
What are the types of mating systems ?
-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.
Who has courtship rituals ?
-Many animals have mate-selection courtship rituals
-Successful courtship behaviour in birds and fish can be a result of species-specific sign stimuli and fixed action pattern responses
This means individuals mate when more fertile, increases chance of successful reproduction, ensures animal courts member of same (correct) species
What does sexual selection select for ?
Sexual selection selects for characteristics that have little survival benefit for the individual, but increase their chances of mating
Links to sign stimuli, male sign shows to female is reproductively ready and genetically fit, so will likely be receptive to mating attempts, increasing chance of mating.
How do males and female physically compare in different species ?
-Many species exhibit sexual dimorphism as a product of sexual selection: females are generally inconspicuous; males usually have more conspicuous markings, structures and behaviours.
-Reversed sexual dimorphism occurs in some species (When the female of a species has more distinctive traits, like size (larger), color, brightness or strength, than the male
Sexual dimophism = distinct difference in size or appearance between the sexes of an animal in addition to the sexual organs themselves.
What is female choice ?
-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.
What is a lekking species ?
-Some bird species exhibit lekking behaviour. In lekking species, males gather to display at a lek, where female choice occurs
-Dominant males occupy the centre of the lek, with subordinates and juveniles at the fringes as ‘satellite’ males. During the display, female choice occurs.
