What is a keystone species?

A keystone species is defined as one whose impact on its ecosystem is disproportionately large relative to its biomass. This means that even though a keystone species might not be the most abundant organism in its ecosystem, its presence and activities have a profound effect on the structure and health of the community. This concept highlights the essential role that certain species play in maintaining the ecological balance and biodiversity of an environment.

For example, a predator might control the population of herbivores, which in turn affects the plant community and the overall structure of the ecosystem. Without the keystone species, the ecosystem can undergo significant changes, potentially leading to a decline in biodiversity and alterations in habitat.

In contrast, some incorrect options suggest that keystone species either have little effect on their ecosystems, are always predators, or are the most abundant species. These statements do not align with the established understanding of what a keystone species is and highlight misconceptions about the roles different species can play within ecological communities.