Integrate Two Texts
RI.4.9
Read Text 1 and answer the question under it.
Text 1: What a Beaver Dam Does
A beaver does not build a dam for shelter. It builds one to make a pond, and it lives in a lodge in the pond. The dam raises the water so the lodge entrance stays underwater. A predator that cannot swim cannot get in. But the pond does far more than protect one family. Behind a dam, water slows, and slow water drops the silt it carries. Over years this builds rich wet ground. That ground holds water in a drought and holds it back in a flood. It supports plants, insects, amphibians and birds that were not there before. Where beavers have been reintroduced, the number of species in a valley typically rises within five years.
- 1. How soon does species number typically rise after beavers return?
Text 2: The Wolves and the Rivers
Wolves were shot out of Yellowstone by 1926. Fourteen were brought back in 1995. With no wolves, elk had grazed the valleys freely for seventy years. Young willow and aspen were eaten as soon as they grew. The wolves killed some elk. More importantly, they changed where elk would stand still. Open valley floors became dangerous, so the elk stopped lingering there. Willow and aspen grew back along the rivers. Beavers, which need willow, returned. Their dams made ponds. Roots held the banks. The rivers narrowed, deepened and moved less. Some researchers describe this as wolves changing the shape of rivers, though others argue the effect has been overstated.
- 1. How is a beaver dam different from a coral reef?
- 2. How is a beaver dam like a coral reef?
- 3. How is this text more cautious than the beaver text?
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