Balance in Lake Ecosystems

Objectives:

1. The student will be able to state what happens to an ecosystem if an element of that system is altered or removed

Materials Needed:

• Computers connected to the Internet
• Lakes Worksheet #S-2 (Upsetting the Balance)

Activity:

Discuss what happens if an ecosystem gets altered (added to, taken away, or elements increased or decreased)

Divide the class into groups. Hand out "Lakes Worksheet #S-2". Have students discuss and fill out sheet as per instructions on sheet.

For discussion purposes:

Ecosystems are all about balance! Nature has it so populations of various organisms are kept steady within that population. Without human interference things carry on nicely. If the system gets interfered with or if new things get introduced, the balance gets thrown off.

Anglers like certain types of fish depending on the sport they provide or how good they are to eat. The trout population in a lake, for instance, can be overfished. Suddenly the balance is thrown off. Other fish (e.g. northern pikeminnow, suckers),when they are small, don't get eaten by trout and their population explodes.

In Okanagan Lake a certain type of shrimp were introduced so the fish would have more feed and grow bigger. These shrimp ate the tiny organisms that baby fish like. The baby fish couldn't survive, The fish population went way down and is in big trouble. The shrimp population, without natural enemies, has exploded and created all kinds of problems