All living things need to feed to get energy to grow, move and reproduce. But what do these living things feed on? Smaller insects feed on green plants, and bigger animals feed on smaller ones and so on. This feeding relationship in an ecosystem is called a food chain. Food chains are usually in a sequence, with an arrow used to show the flow of energy.
A food chain is not the same as a food web.
A food web is a network of many food chains and is more complex.
See the food web illustration below—you can pick out a basic food chain from the web: Green plants Grasshopper Frog Bird Hawk
In the diagram above, arrow shows the direction of who is eating what.
Energy is transferred along food chains from one level to the next. Some of the energy is used up in growth, reproduction repair, movement and other ways, and not made available to the next level.
Shorter food chains retain more energy than longer chains. Used up energy is absorbed by the environment.