A heterotroph (Greek heterone = (an)other and trophe = nutrition) is an organism that requires organic substrates to get its carbon for growth and development. A heterotroph is known as a consumer in the food chain. Contrast with autotrophs which use inorganic carbon dioxide or bicarbonate as sole carbon source. All animals are heterotrophic, as well as fungi and many bacteria. Some parasitic plants have also turned fully or partially heterotrophic, whereas carnivorous plants use their flesh diet to augment their nitrogen supply, but are still autotrophic. Heterotrophs are unable to synthesize organic, carbon based compounds independently from the inorganic environment's sources (e.g. Animalia, unlike Plantae, cannot photosynthesize) and therefore must obtain their nutrition from another heterotroph or an autotroph. 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 and must obtain carbon in an organic form
- chemoheterotroph — obtains energy from the consumption of organic molecules and an organic form of carbon
In simpler terminology, a heterotroph is an organism that is incapable of making its own food from light or inorganic compounds, and feeds on organisms or the remains of other organisms to get its necessary energy to survive.
