AutotrophAn autotroph is an organism that produces its own organic compounds from inorganic substances (e.g., minerals) using either light or chemical bonds as an source of energy. Plants and other organisms using photosynthesis are photoautotrophs; bacteria that use utilize inorganic compounds, such as hydrogen sulfide or ferric iron, for energy are chemoautotrophs.
Autotrophs are a vital part of the food chain. They take energy from the sun or from inorganic sources and convert it into a form (organic molecules) that other organisms (heterotrophs) can use as food, obtaining energy by breaking down the organic molecules. Heterotrophs, like animals, fungi, and most bacteria and protozoa, depend on autotrophs for energy and for the raw materials to make complex organic molecules. Even carnivorous animals ultimately rely on autotrophs because the energy gained from the prey comes from the autotrophs eaten by the prey.
See also: Primary nutritional groups