Select the correct answer. Which statement best describes a keystone species? A. It has little genetic variation. B. It has an extremely high population. C. It remains unaffected by all environmental changes. D. It has a strong influence on the ecosystem. E. It's the first species to populate a new ecosystem.

The correct answer is option D. Its absence would affect many organism present in the community.

Answer: D. It has a strong influence on the ecosystem.

A keystone species is a non-abundant species in an ecosystem. This species is important for the survival of the other species of the ecosystem. It plays nearly the same role in all the ecological communities that is it maintains the structural and functional integrity of the community. The extinction of a keystone species can lead to the extinction of the numerous other species sustaining in an ecosystem. They can also be predators which can feed upon other species so as to maintain a balance in the ecosystem. Therefore, these have the strong influence in the ecosystem.

For example: American alligator: American alligators use their tails to form burrows which allows them to stay warm during winters. But they are also predators, which eat upon other species of fishes and others so as to maintain the balance of nature.

Beavers: They make natural dam which provides shelter to may fish species.