Question

. Bird species may decrease egg size and increase clutch size, increase egg size and decrease clutch size, or decrease egg and clutch size. Describe the advantages and disadvantages of each strategy. Is one strategy better than any other? Why or why not?

B) State Lack’s Hypothesis and describe why it is short-sighted

Answer 1

QUESTION-1

ANSWER

Bird species may decrease egg size and increase clutch size, increase egg size and decrease the clutch size, or decrease egg and clutch size.

These are all trade-off characters organisms adopt in their life cycle according to the environment.

The trade-off is the number of offsprings produced versus the timing of reproduction.

Animals invest energy and parental care to take care of their children.

Advantages and disadvantages of each strategy-

1. Decrease egg size and increase clutch size

Advantages-

• more offsprings are produced in a single reproductive course.

Disadvantages-

• Less parental care
• Less investment of energy in taking care of offsprings
• Offsprings survive on their own.

2. Increase egg size and decrease the clutch size

Advantages-

• Large investment energy in each offspring.
• High parental care
• The number of offspring can survive is more.

Disadvantages-

• Few numbers of offsprings are produced.

3.  Decrease egg and clutch size

Advantages-

• High parental care

Disadvantages-

• Though there will be high parental care the number of offsprings will be very low.
• As the egg size will be very small the offsprings will have to depend on parents for a longer time.
• The cytoplasm will have lesser nutrients for the development of the offsprings.

The better strategy amongst these three- increase egg size decrease clutch size.

The number of offsprings will be low as the clutch size is decreased.

The egg size increases so the cytoplasm contains all the nutrients for the better growth and development of the offsprings.

The parents can invest maximum energy in parental care.

Each offspring gets more sources of food and fuel.

B. Lack’s Hypothesis

Lack proposed a relationship between the altitude and the clutch size in birds.

Altitude increases as we move away from the equator.

According to Lack the clutch size increases in the bird living in the poles as compared to the birds present near the equator.

This hypothesis was short-sighted because it was not replicated in the fields.

The other experiments carried out to support the hypothesis failed.

GOOD LUCK.