Question

Wolves were reintroduced to Yellowstone National Park in 1995. They began to hunt the abundant elk population, so elk numbers decreased. The elk carcasses provided food for other predators, like foxes, coyotes, and bears, so all of their populations increased. Elk used to overgraze on willow plants; now that willows are growing back, beaver numbers are increasing, because they prefer the slow-moving water that willows cause.

Which of these species is a keystone species?

(1 point)
Responses

willows
willows

elk
elk

wolves
wolves

bears

Answer 1

The correct response is **wolves**. Wolves are considered a keystone species because their predation helps regulate the population of elk, which in turn has a cascading effect on the entire ecosystem, including the vegetation and other animal populations.