Question

Read the passage and answer the following question.

A total of 12 bird species having distinct diets, behavior, coloration and beak shapes inhabit a large volcanic island in the South Atlantic 500 miles from the Coast of Africa not found on the mainland. Two species are flightless herbivores. A bird found on the mainland is related to these bird species but it does not fly over water but can occasionally survive at sea in a storm. There are no reptiles, mammals or amphibians on the island, although there are many insect and plant species.

Two of the bird species on the island are herbivores that both inhabit the same species of tree and eat the fruit the tree produces year-round. Which of the following helps both species to inhabit the tree without competing for resources?

• A. One species lives in the top 30 percent of the tree and the other species lives in the lower 70 percent.
• B. One species is nocturnal and the other is active during the day.
• C. Reproductive isolation exists.
• D. The species have differing beak shapes.
• E. One species must become extinct.

Answer 1

The correct option is A One species lives in the top 30 percent of the tree and the other species lives in the lower 70 percent.

This phenomenon is called Resource partitioning. When the resources in a niche are limited, so as to avoid the competition species divide the resources accordingly.

According to R* rule of limited resources of ecology, If two species are living in a resource limiting space, the species which can survive in the lowest equilibrium of resource will only resist the extinction. Coexistence is only possible if each species have the low R* on that resource.

So, the answer is 'One species lives in the top 30 percent of the tree and the other species lives in the lower 70 percent'.