The Nurse Shark is an example of a keystone species. A keystone species is a species that are not abundant in a community but exerts a strong control on the structure of an ecological community. Nurse sharks consume a variety of different animals including coral, fish, shrimp, squid, and shellfish. By limiting the populations of these animals, plankton, phytoplankton, smaller fish, and other prey in the nurse shark’s diet are able to thrive. If the nurse shark was not part of the ecosystem, its prey would overpopulate and cause a mass die off of their populations because the prey would consume all its resources and make them extinct.