Biology

The correct answer is C. Their presence or absence affecting many other species in the ecosystem.

Keystone species have a disproportionately large impact on their ecosystem relative to their abundance. Their presence or absence can significantly influence the structure, diversity, and functioning of the ecosystem. The removal of a keystone species often leads to dramatic changes in the community, affecting many other species.

Explanation of other options:

A. Being the most numerous species in their habitat: Keyst...