How does energy flow through the food web?

Plants harvest their energy from the sun during photosynthesis. This energy can then be passed from one organism to another in the food chain.

The organism that obtains energy from sunlight is called the producer. Often these are plants but in some circumstances it can be bacteria.

Even though it is producers that bring energy into the food chain from the sun it is consumers that make up the majority of the food chain. These can be predators, scavengers and parasites.

When a plant is eaten by a primary consumer, only 10% of the energy is passed on.

The low percentage of transferred energy can be attributed to different reasons like some of the organism not being eaten, incomplete digestion of the eaten organism, energy lost in excretory processes or energy lost as heat.

Consumers pass 20% of their energy onto other consumers. This is because they are more efficient than plants at passing on the energy. A lot of the energy is lost in excretion and some is lost in trying to maintain a constant body temperature.

When producers or consumers die they will be fed on by decomposers. Decomposers break complex materials into simple components after producers and consumers die, using up the energy they contain. In this way, minerals and elements needed by plants are released in a form that can be absorbed by them.