Autotrophs and heterotrophs differ in the way they obtain energy; autotrophs make their own energy whereas heterotrophs must consume other organisms to get their energy. Autotrophs are the producers of ecosystems, which means they are the providers of energy for the rest of the organisms within the ecosystem.
Heterotrophs and autotrophs are dependent on each other in food chains and food webs. Autotrophs convert the energy they obtain into a form they can use. Plants, algae and protists like the Euglena are autotrophs. A common type of autotroph, the photoautotroph, uses light from the sun to change carbon dioxide and water into a sugar called glucose. This sugar is what the autotroph and other organisms in the ecosystem use for energy. Not all autotrophs are photoautotrophs; chemoautotrophs use convert certain chemicals into the energy they need.
Heterotrophs consume autotrophs or other heterotrophs for energy. Food chains consist of an autotroph and a series of heterotrophs. Primary consumers are heterotrophs that consume autotrophs. Secondary and tertiary consumers are heterotrophs that eat primary and secondary consumers, respectively. These organisms are organized into trophic levels. At each trophic level, only 10 percent of the energy of the previous trophic level is retained; the other 90 percent of the energy is lost, mostly as heat. The amount of energy represented at each trophic level is represented in a pyramid of energy.