Radiant energy from the sun is converted to chemical energy and stored in the form of sugar and starch molecules by producers. All organisms are linked through feeding relationships. The energy stored in producers is transferred to each organism that eats a producer, and then to other organisms that feed on these consumers. There are many feeding relationships in an ecosystem, but energy always flows from producers to various consumers.

A food chain is a series of steps in which organisms transfer energy by eating and being eaten. The food chain below illustrates a food chain that is found in a prairie ecosystem. The arrows in a food chain show the transfer of energy from one organism to another. Notice that the arrows point in the direction of the energy flow. The point of the arrow goes to the organism that is taking in the energy or the organism that is doing the eating. The sun provides energy for the grass. The grass provides the energy for the caterpillars that eat the grass. The snake gets its energy by eating the caterpillar. The hawk eats the snake to obtain its energy.

Interactive exercise. Assistance may be required. Use the pull down menu to label each organism as producer or consumer.

Interactive exercise. Assistance may be required. The feeding relationships differ from ecosystem to ecosystem; therefore the food chains differ from one ecosystem to another. Scroll over each organism pictured below to learn more about its feeding habits. Decide which organism belongs in the indicated location in the food chain.

Each step in a food chain is called a trophic level. Primary producers always make up the first trophic level. Various consumers occupy every other level.

Each consumer relies on the trophic level below it for energy. Ten percent of the available energy on each level is passed to the next trophic level.

The image below shows the example prairie food chain with the trophic levels noted under each organism.

Sources for images used in this section, as they appear, top to bottom: