2l- Parental investment Flashcards
What are characteristics of a female egg gamete?
- bigger
- nutrient filled
- more expensive to produce
- limited in number and produced infrequently
- if fertilised, there are greater costs to the female
There is greater investment from females than from males, what forms does this take in mammals and in non-mammals?
mammals- investment in the uterus and in gestation
non-mammals- investment in egg structure
Parental investment is costly, but why is it necessary?
It increases the probability of production and survival of young
What is the classification of r-selected and k-selected organisms based on?
Level of parental investment in offspring and number of offspring produced
What are 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 receive a smaller
energy output) - limited parental care
- most offspring will not reach adulthood
What are characteristics of k-selected species?
- larger
- live longer
- mature more slowly
- can reproduce many times in their lifetime
- produce relatively few but larger offspring
- high level of parental care
- many offspring have a high probability of surviving to adulthood
What are characteristics of the male sperm gamete?
- small
- have no nutrients
- cheap to produce
- continuously made throughout life
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
When does internal fertilisation occur?
When the male and female gametes fuse inside the body
When does external fertilisation occur?
When the male and female gametes fuse outside the body
What is a benefit of external fertilisation?
- very large numbers of offspring can be produced
What are some costs of external fertilisation?
- many gametes predated or not fertilised
- no or limited parental care
- few offspring survive
What are some benefits of internal fertilisation?
- increased chances of successful fertilisation
- fewer eggs needed
- offspring can be retained internally for protection and/or development
- higher offspring survival rate
What are some costs of internal fertilisation?
- a mate must be located which requires energy expenditure
- requires direct transfer of gametes from one partner to another
