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

Option D, it has a strong influence on the ecosystem

Explanation:

Keystone species are an essential part of an ecosystem and their functions/mark cannot be replaced by any other organism. Once the keystone species is removed from an ecosystem, the ecosystem struggles to sustain or it changes radically. A keystone species in majority of ecosystems/food web is a predator but this is not true in all ecosystems/or with all keystone species.

For example - there was a trophic cascade when the Gray wolves in the greater Yellowstone ecosystem were removed.

The answer is D

One way to remember this is when you are building a bridge there is one piece right in the middle that keeps the whole thing from collapsing that is called the key-stone. If a keystone species goes extinct then the rest of the ecosystem will crumble around it.