Are ecosystem populations stable?

All ecosystems are populated by plants and animals that depend on each other in various ways. For example, plants are a food supply for small animals, which in turn are a food supply for predators.

Do you think that these systems of predators and prey are stable? How much do populations fluctuate? Can they fluctuate and still be called “stable”?

This activity uses a model explore the stability of predator-prey ecosystems.

For example, imagine that you have a population of squirrels that eat acorns. The local owls hunt the squirrels as their main source of food.
Suppose there is a drought (shortage of water) for three years, and the production of acorns drops to 1/4 of its normal level. Then on the fourth year there is lots of rain and the supply of acorns is twice as high as normal for two years.

Draw a graph showing what you think the squirrel and owl populations will do over these years. Make a graph with “years” on the horizontal axis. Label the vertical axis “number of animals” and make two lines — one for squirrels and one for owls.

The Concord Consortium: http://www.concord.org/

See the link below for the interactive resource.  After creating a free account, you will have access to all ITSI-SU Math and Science interactive resource and lessons.

http://itsisu.portal.concord.org/activities/44.jnlp?teacher_mode=true

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