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

bears
bears

willows
willows

elk
elk

wolves
wolves

Answer 1

Wolves are considered a keystone species in this scenario. Keystone species have a disproportionately large impact on their environment relative to their abundance, and the reintroduction of wolves to Yellowstone led to a cascade of ecological changes, affecting the populations of elk, which in turn allowed for the recovery of willows and the subsequent increase in beaver populations. Therefore, the correct answer is:

**wolves**