Definition - What does Keystone Species mean?
A keystone species is species of plant or animal life which plays a critical or unique role in the function of an ecosystem. All species in a habitat rely on each other for the effective functioning of that habitat, but keystone species play a larger role and if they were removed this would cause a large negative impact on life or the complete extinction of all species.
Safeopedia explains Keystone Species
There is a large list of keystone species and these all have unique characteristics which help our ecosystem. The american alligator, for example, uses its tail to make burrows to stay warm and after they move on, these burrows are used by other species as a source of water after they fill up. The american alligator also helps to keep the numbers of their prey in check as a predator.