Food Chains and Webs

Energy flows from the sun through producers to consumers.

Producers and Consumers

Producers (plants) make their own food. Primary consumers eat producers; secondary consumers eat primary consumers; tertiary consumers eat secondary consumers. Decomposers break down dead matter.

Energy Loss

Only about 10% of energy passes to the next trophic level; the rest is lost as heat, movement and waste. This is why food chains rarely have more than five levels.

Food Webs

A food web joins several food chains and shows how organisms are interconnected. Removing one species can affect many others.

Practice

1. Draw a food chain with four trophic levels.
2. Explain why energy decreases at each level.
3. Predict what happens if all decomposers disappear.

Recap

Energy flows from producers through consumers. Food webs show interdependence, and energy is lost at each level.