An
autotroph ("
self-feeding", from the
Greek autos "self" and
trophe "nourishing") or
producer, is an organism that produces complex
organic compounds (such as
carbohydrates,
fats, and
proteins) from simple substances present in its surroundings, generally using energy from light (
photosynthesis) or inorganic chemical reactions (
chemosynthesis). They are the
producers in a
food chain, such as
plants on land or
algae in water, in contrast to
heterotrophs as consumers of autotrophs. They do not need a living source of energy or organic
carbon. Autotrophs can
reduce carbon dioxide to make organic compounds for biosynthesis and also create a store of chemical energy. Most autotrophs use water as the
reducing agent, but some can use other hydrogen compounds such as hydrogen sulfide.
Phototrophs (green plants and algae), a type of autotroph, convert electromagnetic energy from sunlight into chemical energy in the form of
reduced carbon.
