To understand what a keystone species is, we need to look closely at the options given:
- a) A species that has a disproportionate effect on its environment relative to its abundance: This is a correct statement. Keystone species play a critical role in maintaining the structure of an ecological community, and their impact on the environment is significant compared to their population size. For instance, the removal of a keystone species can lead to dramatic shifts in ecosystems.
- b) None of these are true about a keystone species: This statement is false. We have established that option a is indeed a true description of a keystone species.
- c) It can only be a species: This statement is misleading. While the term ‘keystone species’ typically refers to a specific species, the concept can be applied more generally. It emphasizes the importance of particular organisms within their ecosystems, but it’s not limited to just one species—it can apply to multiple species within a community.
In summary, the correct answer here is option a. Keystone species are vital for their ecosystems and serve an important function that is not proportional to their abundance.