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.

Question

Which of these species is a keystone species?

(1 point)
Responses

bears
bears

wolves
wolves

elk
elk

willows

Answer 1

The keystone species in this scenario is wolves. Keystone species have a disproportionately large impact on their environment relative to their abundance. By preying on elk, wolves help control the elk population, which in turn allows willows and other plant species to thrive, leading to a cascade of effects on other species in the ecosystem.