Final answer:
Keystone species play a crucial role in their community, while endangered species are at risk of extinction. Protecting keystone species can indirectly benefit other endangered species.
Step-by-step explanation:
Keystone species are species that play an important role in their community, and changes in their numbers can affect many other species. Endangered species, on the other hand, are species that are at risk of extinction. While not all keystone species are endangered, they can receive special consideration in conservation efforts because protecting them can indirectly benefit other endangered species.