keystone species
A keystone species is a species that has a disproportionately large impact on its environment relative to its abundance. These species help maintain the structure of an ecosystem, influencing the types and numbers of other species present. For example, the sea otter is a keystone species in coastal ecosystems because it preys on sea urchins, which, if left unchecked, can overgraze kelp forests.
The removal of a keystone species can lead to significant changes in the ecosystem, often resulting in a decline in biodiversity. This concept highlights the importance of certain species in maintaining ecological balance, as seen with the gray wolf in Yellowstone National Park, which helps regulate herbivore populations.