Describe the effects that the dams built by beavers (a keystone species) have on other types of organisms.

Beavers and their dams play an important role in nature. Because of the dramatic effects their dams have on surrounding ecosystems, these mammals are considered a keystone species. By constructing dams they create wetlands -- lush environments which attract fish, ducks, frogs and other creatures.

Explanation:

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.