What is a keystone species?

A keystone species is defined as a species that has a disproportionately large impact on its ecosystem relative to its abundance or biomass. This means that the presence or absence of a keystone species can significantly influence the structure and health of the ecosystem. Keystone species often play critical roles in maintaining the balance of their environments, such as through predation, competition, or mutualistic relationships.

For example, if a keystone predator is removed from an ecosystem, it may lead to an explosion of prey species that can overconsume vegetation, resulting in habitat degradation. Conversely, maintaining the population of a keystone species can help sustain biodiversity and ecological stability. Understanding this concept is crucial for conservation efforts, as protecting keystone species can have far-reaching benefits for the entire ecosystem.

The other options, while describing different aspects of species and ecosystems, do not capture the unique and pivotal role that keystone species play in maintaining ecological balance. Being the most numerous, the largest, or capable of surviving in harsh conditions does not necessarily imply that a species has a significant or controlling influence on its ecosystem’s dynamics.