PSSA Practice Test 6

Busy Builders of the Pond

¹Few animals change the land as much as people do. One that does is the North American beaver, the largest rodent on the continent. With its sharp teeth and strong, flat tail, a beaver can turn a small, fast stream into a wide, quiet pond. Scientists sometimes call beavers "ecosystem engineers" because they build and reshape places where many other living things make their homes.

²Teeth That Never Stop A beaver's front teeth are bright orange. The color comes from iron, which helps make the outer layer of the teeth extra hard. These teeth never stop growing, so a beaver must keep gnawing on wood to wear them down. A beaver can chew through a small tree in just a few minutes.

³Building a Dam Beavers build dams across streams by piling up sticks, branches, rocks, and mud. They push mud into the gaps with their front paws, packing the dam tight so that water backs up behind it. As the water rises, it spreads out to form a pond. Some beaver dams are only a few feet long. Others stretch hundreds of feet.

⁴Beavers seem to listen to their dams. The sound of running water tells them that there may be a leak, and they hurry to patch it with more mud and sticks. In experiments, when scientists played the sound of running water from a hidden speaker, beavers covered the speaker with sticks and mud.

⁵A Safe Home In the pond, many beavers build a lodge, a dome-shaped home made of the same sticks and mud. The entrances are underwater, so wolves, coyotes, and other predators cannot easily get inside. Inside, above the water line, there is a dry room where the beaver family sleeps and raises its young. In fall, beavers store branches underwater near the lodge so they will have food all winter, even when the pond freezes over.

⁶A Pond Full of Life A beaver pond does not help only beavers. The still, deep water becomes a home for fish, frogs, turtles, and insects. Ducks and herons come to feed. Moose and deer drink at the edges. Trees that drown in the rising water become perches for birds and homes for woodpeckers. Even after the beavers move away, the wet meadow left behind can stay full of plants and animals for many years.

⁷Beaver ponds help people, too. The dams slow down rushing water after heavy rains, which can reduce flooding downstream. As water sits in the pond, mud and dirt settle to the bottom, so the water that flows out is cleaner. Ponds also soak water into the ground, which helps nearby streams keep flowing during dry summers.

⁸Welcome Back By the early 1900s, so many beavers had been trapped for their fur that they had disappeared from large parts of North America. Today, laws protect them in many places, and beavers have returned to many streams where they once lived. In some areas, people are even bringing beavers back on purpose so that the animals can help repair wetlands.

Student Draft

¹(1) Beavers are animals that live in ponds. (2) In "Busy Builders of the Pond," the author shows that beavers change the places where they live by building dams that create ponds full of life.

²(3) First, beavers build dams that turn streams into ponds. (4) They pile up sticks, rocks, and mud. (5) ______ the water backs up and spreads out.

³(6) The new pond becomes a home for many animals. (7) The author says that fish, frogs, turtles, and insects live in the still water. (8) Ducks and herons come to eat there too.

⁴(9) Beaver ponds also help people. (10) The dams slow down water after storms. (11) This means there is less flooding.

⁵(12) Beavers have orange teeth.