Educator Resources

Class Discussion
Establish Prior Knowledge

Review the components of a food web with your students, including primary consumers, secondary consumers, and producers. Ask them what happens to the biodiversity of an ecosystem when a top predator disappears or is removed. Discuss what the long-term consequences might be.


Have students view the Snapshot and read the synopsis. Use the following questions to guide discussion.

1. What two plants are in decline in Yosemite Valley?

2. What do scientists believe is the reason for the plants’ decline?

3. What is a “trophic cascade?”


  • If park officials do nothing what might happen to the California black oak and the evening primrose? What might happen to the population of mule deer?
  • What do you think can be done to bring the biodiversity of the Yosemite Valley environment back into balance?


Students may be interested to learn what happened when wolves were reintroduced at Yellowstone National Park.Wolves Help Aspen Trees Grow (September 3, 2007)