Autotrophs are organisms that are able to synthesize all the complex organic molecules they require for life using only simple inorganic compounds and an external energy source in a process known as autotrophic nutrition. Autotrophs include most plants, algae, protists, archaea, and some bacteria. The chief inorganic sources of carbon and nitrogen are carbon dioxide and nitrates, respectively. In food chains, autotrophs make up the primary producers, providing energy (as food) for organisms higher up the chain.
Autotrophs can be subdivided into photoautotrophs and chemoautotrophs, depending upon how they derive the energy for their metabolism. Organisms that are not autotrophic are known as heterotrophs. The word comes from the Greek autos = "self" and trophos = "feeder."