Environment: ecosystems and food chains

Start with interactions

An ecosystem includes organisms, non-living surroundings and their interactions. Producers such as green plants capture energy and support consumers. A trophic level describes a feeding position; interconnected chains form a food web.

Decomposers break down dead material and help return nutrients to the system. Energy transfer is inefficient, so a higher trophic level has less available energy. Persistent pollutants can become more concentrated along food chains: this is biomagnification.

Draw and explain

Create your own chain using a plant, a herbivore and a predator. State why each organism occupies that level. Then add decomposers and ask what changes when one population is removed. Avoid treating a species as having the same feeding role in every ecosystem.