Energy flows through ecosystems in one direction, typically from the Sun, through photosynthetic organisms or producers, to herbivores to carnivores and decomposers.

The chemical elements that make up the molecules of living things pass through food webs and are combined and recombined in different ways.

At each link in a food web, some energy is stored in newly made structures but much energy is lost into the environment as heat.

Continual input of energy from sunlight is required to keep this process going.

Energy pyramids are often used to show the flow of energy in ecosystems.