Unit 2: Key Area 4 - Sex and behaviour Flashcards
Compare the number of gametes produced by sperm and eggs
Sperm produces millions of gametes constantly whereas a egg produces only one gamete a month
Compare the size of gametes produced by sperm and eggs
Sperm produces a smaller gamete and an egg produces a larger gamete
Compare the structure of gamete for sperm and egg
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Compare the chances of reproductive success for males and females and why
Males have higher chances of reproductive success as they produce more gametes and smaller gametes.
Whereas
Females have lower chances reproductive success as they produce less eggs and larger gametes
Compare the chances of passing on genes for males and females and why
Males have higher chances of passing on genes as there is no investment needed.
Whereas
Females have lower chances passing on genes as they invest in the egg structure in non-mammals or in the uterus and during gestation in mammals.
what is an advantage and disadvantage of parental investment
Parental investment is costly but increases the probability of production and survival of young
What are is classification of r-selected (r-strategists) and K-selected (K-strategists) organisms based on
Classification of r-selected (r-strategists) and
K-selected (K-strategists) organisms are based
on the level of parental investment in offspring and number of offspring produced
Compare the characteristics of r-selected species and K-selected species
Size
Characteristics of r-selected species:
smaller
Characteristics of K-selected species:
larger
Compare the characteristics of r-selected species and K-selected species
Life span
Characteristics of r-selected species:
have a shorter generation time
Characteristics of K-selected species:
live longer
Compare the characteristics of r-selected species and K-selected species
Mature time
Characteristics of r-selected species:
mature more rapidly
Characteristics of K-selected species:
mature more slowly
Compare the characteristics of r-selected species and K-selected species:
Timing of first reproduction
Characteristics of r-selected species:
reproduce earlier in their lifetime
Characteristics of K-selected species:
reproduce later in life
Compare the characteristics of r-selected species and K-selected species
How many offsprings produced per reproductive period
Characteristics of r-selected species:
produce a larger number of smaller offspring
Characteristics of K-selected species:
produce relatively few larger offsprings
Compare the characteristics of r-selected species and K-selected species
How many times do they reproduce in a lifetime
Characteristics of r-selected species:
reproduces often only once
Characteristics of K-selected species:
reproduce many times
Compare the characteristics of r-selected species and K-selected species
Level of parental care
Characteristics of r-selected species:
limited parental care
Characteristics of K-selected species:
high level of parental care
Compare the characteristics of r-selected species and K-selected species
Likelihood of reaching adulthood
Characteristics of r-selected species:
most offspring will not reach adulthood
Characteristics of K-selected species:
many offspring have a
high probability of surviving to adulthood
Compare the characteristics of r-selected species and K-selected species
Energy input
Characteristics of r-selected species:
small energy input
Characteristics of K-selected species:
larger energy input
Compare the environment of r-selected species and K-selected species
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
Comparison of costs and benefits of external and internal 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
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
What are the different types of mating systems
- polygamy
- polygyny
- polyandry
- monogamy
Define a Monogamy mating system
Monogamy: the mating of a pair of animals to the exclusion of all others
Define a Polygamy mating system
Polygamy: individuals of one sex have more than one mate
Define a Polygyny mating system
Polygyny: one male mates exclusively with a group of females
Define a Polyandry mating system
Polyandry: one female mates with a number of males in the same breeding season
What do many animals have when choosing a mate
Many animals have mate-selection courtship rituals
What is a successful courtship behaviour in birds and fish a result of
Successful courtship behaviour in birds and fish can be a result of species-specific sign stimuli and fixed action pattern responses
Why is sexual selection important
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
Many species exhibit sexual dimorphism as a product of sexual selection
How is sexual dimorphism expressed in most cases
Females are generally inconspicuous; males usually have more conspicuous markings, structures and behaviours.
How is sexual dimorphism expressed in some cases
Reversed sexual dimorphism occurs in some species
What does female choice involve
Female choice involves females assessing honest signals of the fitness of males
Describe honest signals
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 what happens at a lek
In lekking species, males gather to display at a lek, where female choice occurs
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.
Describe male to male rivalry
Males will fight for dominance and access to females, often using elaborate ‘weapons’ such as antlers, tusks, horns.
what does success in male to male rivalry result in
Success in male-male rivalry through conflict (real or ritualised), increases access to females for mating
