heterotroph

heterotroph, living organism that obtains its energy from carbohydrates and other organic material. All animals and most bacteria and fungi are heterotrophic. In contrast, autotrophs are organisms that use inorganic substances as energy sources and carbon dioxide as a carbon source.

A heterotrophs, or chemoorganotrophy (Greek heterone = (an)other and trophe = nutrition), is an organism that requires organic substrates to get its chemical energy for growth and development. This contrasts with autotrophs such as plants which are able to directly use sources of energy such as light to produce organic substrates from inorganic carbon dioxide.

Heterotrophs are known as consumers in food chains and obtain organic carbon by eating other heterotrophs or autotrophs. All animals are heterotrophic, as well as fungi and many bacteria. Some animals, such as corals, form symbiotic relationships with autotrophs and obtain organic carbon in this way. Furthermore, some parasitic plants have also turned fully or partially heterotrophic, while so-called carnivorous plants consume animals to augment their nitrogen supply but are still autotrophic.

For a species to be termed a heterotroph, it must obtain its carbon from organic compounds. If it obtains nitrogen from organic compounds, but not energy, it will be deemed an autotroph. If a species obtains carbon from organic compounds then there are two possible subtypes of these heterotrophs:

• photoheterotroph — obtains energy from light but must still obtain carbon in an organic form
• chemoheterotroph — obtains energy from the consumption of inorganic molecules and an organic form of carbon

See also

• Primary nutritional groups
• Auxotrophy
• Autotroph