Earth is an interacting system of Air, Water, Ice, Rock, and Life. These five things link together to make our planet hum. They’re a team. Scientists call them systems or spheres. Each system plays an important role, and they all depend on each other.

The video below shows what happened to the ecosystem structure in Yellowstone National Park after the introduction of wolves in 1995.

[youtube id=”ysa5OBhXz-Q” width=”800″ height=”450″ autoplay=”no” api_params=”” class=””]


Wolves and other top predators are keystone species – they prevent overpopulation of prey species, encouraging a balance in nature. One of the most exciting scientific findings of the past half century has been the discovery of widespread trophic cascades. A trophic cascade is an ecological process which starts at the top of the food chain and tumbles all the way down to the bottom.

Click here to search Earth Science STEM activities in our STEM Activity Clearinghouse.
Click here to view a variety Earth Science exhibition posters.