Trophic levelsSpec 4.6
In short
A trophic level is the position of an organism in a food chain. Producers, such as plants and algae, are level 1, primary consumers (herbivores) are level 2, secondary consumers are level 3 and tertiary consumers are level 4. Decomposers, which are bacteria and fungi, secrete enzymes onto dead matter and waste, and the small soluble molecules diffuse in.
A trophic level is the position of an organism in a food chain. Trophic levels are numbered, starting at level 1 with the producers. Further levels are numbered according to how far the organism is along the food chain.
| Trophic level | Organisms | Name |
|---|---|---|
| Level 1 | Plants and algae make their own food | Producers |
| Level 2 | Herbivores eat the producers | Primary consumers |
| Level 3 | Carnivores that eat herbivores | Secondary consumers |
| Level 4 | Carnivores that eat other carnivores | Tertiary consumers |
Decomposers
Decomposers break down dead plant and animal matter and waste by secreting enzymes into the environment. Small soluble food molecules then diffuse into the microorganism. Decomposers are bacteria and fungi.
(opens full size in a new tab)Decomposers secrete enzymes outside their bodies, onto the dead material. They do not take in the dead material and then digest it.
Written and checked against the Edexcel IGCSE Science Double Award (4SD0) specification · Updated October 2026