Wolves and Elk in Yellowstone Since 1995

Use the fact file organizer as a reading task, then the beaver sheet as a graphing lab. Close with the Yellowstone sheet to discuss how scientists weigh evidence.

Trace the effects of 31 gray wolves released in Yellowstone on elk, willows and songbirds. The directions on the page read: Read the text and study the food web. Then answer the questions on page 2. An answer key is included.

Yes, both. We made it for 8th grade ecosystems, and it works the same at home or at school. At home, a student can work through it alone and then go over it with you, which shows quickly what is solid and what needs another look. In class it works as independent practice, homework or a warm-up, and you can print one copy or a full set.

Its larvae tunnel through the layer just under the bark and eat the tissue that carries water and food through the tree. An infested tree usually dies within a few years. The fact file also covers how it likely arrived in wooden packing material.

A beaver dam backs water into a pond that can spread into a wetland and raise the water table. Ducks, frogs and songbirds gain, while drowned trees and fish that need cold, fast water lose. The beaver sheet graphs pond area and bird species over eight years.

Evidence is a measured fact, such as the elk herd falling to fewer than 4,000 in 2013. A debated claim is an idea scientists still argue about, such as wolves alone making willows grow back. The Yellowstone sheet asks students to sort statements this way.