Trophic levels

Ecology and the environment · Feeding relationships · note 1 of 4

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Trophic levelsSpec 4.6

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.

Food chain of grass, grasshopper, frog and snake labelled trophic levels 1 to 4, with dashed arrows from each to dead plants and animals and their waste; below, decomposers (microorganisms) secrete enzymes onto the dead material and small soluble food molecules diffuse into them. — Every trophic level ends up as dead material or waste. Decomposers secrete enzymes onto it, then the small soluble molecules diffuse in.

Exam tip:

Decomposers secrete enzymes outside their bodies, onto the dead material. They do not take in the dead material and then digest it.