7.4 Food chains

Food chains are how energy passes through an ecosystem

1. Starts with a producer (photosynthetic organism) like grass

2. Primary consumers (eat producers) like mice

3. Secondary consumers (eat primary consumers) like owls

4. Tertiary consumer (eat secondary consumers)

As energy passes up through different levels of consumers, most of it gets lost

Predator prey cycles

• populations of both predator & prey cycle up & down

• Predator population peaks just after prey peak - populations are ‘out of phase’

• Takes a long time for populations to increase / decrease