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

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)
• willows
• bears
• wolves
elk

Answer 1

In this scenario, the wolves are considered the keystone species. A keystone species is one that has a disproportionately large impact on its environment relative to its abundance. In this case, the reintroduction of wolves ultimately led to a series of ecological changes, including a decrease in elk populations, which allowed vegetation like willows to recover, benefiting other species such as beavers. Therefore, the correct answer is:

• wolves