Producers, Consumers and Decomposers

≈ 18 min

Every living thing in an ecosystem has a feeding role. There are three:

1. Producers. Green plants make their own food using energy from the Sun, plus water and air. Nothing else in the ecosystem can do this. Mielies, grass, reeds, seaweed and the tiny green specks floating in dam water are all producers.

2. Consumers. Animals cannot make food, so they must eat. We sort them by what they eat:

Kind of consumer	Eats	South African example
Herbivore	plants only	springbok, cow, locust
Carnivore	other animals	cheetah, fish eagle, jackal
Omnivore	plants and animals	baboon, guinea fowl, people

3. Decomposers. Fungi, bacteria and creatures like earthworms and dung beetles break down dead plants, dead animals and dung. The goodness locked inside goes back into the soil, where producers use it again.

Worked example — a Free State mielie field.

The mielie plant is the producer: it catches the Sun's energy. A field mouse eats mielie kernels, so it is a consumer (a herbivore). A spotted eagle-owl eats the mouse — also a consumer (a carnivore). When the owl finally dies, mushrooms and soil bacteria — the decomposers — break its body down and feed the soil that the next mielie crop grows in.

Trace any meal backwards far enough and you always land on a producer, and then on the Sun.

Which of these is a producer?

An earthworm in the compost heap

A mielie plant in a field

A spotted eagle-owl

A mushroom on a rotting log

An animal that eats only plants, like a springbok, is called a ______.

Imagine every decomposer in a patch of veld suddenly vanished. What would most likely happen over the next few years?

Nothing would change, because decomposers do not feed anything

Dead plants and animals would pile up and the soil would slowly run out of the goodness plants need

The plants would grow much faster because nothing would be rotting

All the carnivores would immediately become herbivores

Look at this food chain: grass → springbok → cheetah. How many consumers are in it?