What is meant by the term keystone species?

The term "keystone species" refers to an organism that has a small population size but a disproportionately large effect on its environment and the structure of its ecosystem. This concept highlights that certain species play critical roles in maintaining the ecological balance, even if they are not the most numerous or dominant. Their presence or absence can significantly influence the types and numbers of other species in that ecosystem, thereby affecting biodiversity and, ultimately, the health of the ecosystem.

For example, a keystone predator might control the population of a particular prey species, preventing it from overgrazing vegetation, which in turn maintains habitat for other organisms. This concept underscores the interconnectedness of species within an ecosystem, where a minor player can fundamentally shape the ecological community's dynamics. Such species are crucial for maintaining the integrity and functionality of their ecosystems.