Energy, Ecosystems And Food Chains
Energy as well as other nonliving materials are transferred in an ecosystem. But, in the case of energy, this transfer process is not perfect. It is often the limitation of energy coming into an ecosystem that controls the number of organisms that can occupy each level of the food chain. This activity will demonstrate these limitations.
- 10 packs of 100 beans/marbles/paper dots (something that can be counted easily)
- Cards designated members of the food chain- sun, grass/trees, rabbits, eagles
Assign students as members of the food chain: one as the sun, ten as grass/trees, five as rabbits, one as an eagle.
The only constant condition in an ecosystem is the amount of energy that comes from the sun. In this activity, sun energy comes in the form of beans/marbles/paper dots. Each packet of 100 beans (or whatever is used) is enough to support one member of the plant category. Have the sun give one packet of energy to each member of the plant group.
Remember that only one percent of the sun's energy that hits the Earth is used by plants. Have each plant take one bean out of their packet, returning the rest to the teacher. This represents energy lost to the system.
Two beans are required to support each rabbit. How many rabbits can be supported?
Have each rabbit give one bean to the teacher. This represents energy lost to the system.
Secondary consumers, like eagles, require a lot of energy. Five beans are needed to support one eagle. How many eagles can be supported?
When eagles die, most of the remaining energy would be released, but a small amount would stay with parts of the eagle that would not decompose quickly. Have the eagle give up 4 beans to the teacher.
Why are fewer organisms found as you move along a food chain? What would happen to other organisms if eagles left the area? If rabbits left?
Where would all of the energy that was lost (given to the teacher) go?