2. Key Area 4 - Sex and Behaviour

Question 1

What is reproductive effort?

Answer 1

To produce the maximum number of surviving offspring using the least amount of energy

Question 2

How does the male reproductive system differ from the female reproductive system?

Answer 2

The number of sperm produced is much greater than the number of eggs. The egg is much larger than the sperm. The egg contains a large food store that provides energy to support the developing zygote until it can feed from the placenta

Question 3

In mammals, how do females have a larger parental investment?

Answer 3

In terms of:
- placental nourishment
- feeding the young (lactation)
- post-natal care and protection

Parental care is costly but it increases the probability of production and survival of young

Question 4

What can organisms be classified as based on their level of parental investment?

Answer 4

r-selected or K-selected

Question 5

Describe the r-selected strategy

Answer 5

environmental condition in which it tends to occur- unstable
body size- smaller
generation time- shorter
development- mature more rapidly
reproduction- earlier in their lifetime
breeding occasion- often only once
number of offspring- larger number
size of offspring- smaller
energy input to offspring- smaller
parental care- limited
offspring survival chance to adulthood- lower (most offspring will not reach adulthood)

Question 6

Describe the K-selected strategy

Answer 6

environmental condition in which it tends to occur- stable
body size- larger
generation time- longer
development- mature more slowly
reproduction-
breeding occasion- reproduce many times in their lifetime
number of offspring- relatively few
size of offspring- larger
energy input to offspring-
parental care- high level
offspring survival chance to adulthood- many offspring have a high probability of surviving to adulthood

Question 7

What is external fertilisation?

Answer 7

Where both types of gametes are shed into water and the sperm swim or are carried by currents to the eggs

Question 8

What is internal fertilisation?

Answer 8

Where eggs are retained within the reproductive tract of the female until after they have been fertilised by sperm inserted into the female by the male