2.4a - Parental Investment

Question 1

Comparison of sperm and egg production - Males

Answer 1

• human male can release 300 million sperm cells in a single ejaculation
• sperm is much smaller than the egg

Question 2

Comparison of sperm and egg production - Females

Answer 2

• human females will release 450 mature eggs in her lifetime
• 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

Comparing one egg to one sperm, greater investment is made by…

Answer 3

females

Question 4

In non-mammals, females invest energy in the…

Answer 4

egg structure

Question 5

In non-mammals, females invest energy in the…

Answer 5

uterus during gestation

Question 6

Parental investment is costly but…

Answer 6

increases the probability of production and survival of young

Question 7

Classification of r-selected and K-selected organisms is based on…

Answer 7

the level of parental investment in offspring and the number of offspring produced

Question 8

Characteristics of r selected species:

Answer 8

• 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 a smaller energy input
• limited parental care
• most offspring will not reach adulthood

Question 9

Characteristics of K-selected species:

Answer 9

• larger and live longer
• mature more slowly
• can reproduce many times in their lifetime
• produce relatively few, larger offspring
• high level of parental care
• may offspring have a high probability of surviving adulthood

Question 10

r-selection tends to occur in…

Answer 10

unstable environments where the species has not reached its reproductive capacity

Question 11

K-selection tends to occur in…

Answer 11

stable environments

Question 12

Benefits of external fertilisation

Answer 12

• very large numbers of offspring produced

Question 13

Costs of external fertilisation

Answer 13

• many gametes predated or not fertilised
• no or limited parental care
• few offspring survive

Question 14

Benefits of internal fertilisation

Answer 14

• increased chance of successful fertilisation
• fewer eggs needed
• offspring can be retained internally for protection and/or development
• higher offspring survival rate

Question 15

Costs of internal fertilisation

Answer 15

• a mate must be located, which requires energy expenditure
• requires direct transfer of gametes from one partner to another