Heterotroph

Cycle between autotrophs and heterotrophs. Autotrophs use light, carbon dioxide (CO2), and water to form oxygen and complex organic compounds, mainly through the process of photosynthesis (green arrow). Both types of organisms use such compounds via cellular respiration to both generate ATP and again form CO2 and water (two red arrows).

A heterotroph (/ˈhɛtərəˌtroʊf, -ˌtrɒf/;[1][2] from Ancient Greek ἕτερος (héteros) 'other' and τροφή (trophḗ) 'nutrition') is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but not producers.[3][4] Living organisms that are heterotrophic include all animals and fungi, some bacteria and protists,[5] and many parasitic plants. The term heterotroph arose in microbiology in 1946 as part of a classification of microorganisms based on their type of nutrition.[6] The term is now used in many fields, such as ecology, in describing the food chain.

Heterotrophs may be subdivided according to their energy source. If the heterotroph uses chemical energy, it is a chemoheterotroph (e.g., humans and mushrooms). If it uses light for energy, then it is a photoheterotroph (e.g., green non-sulfur bacteria).

Heterotrophs represent one of the two mechanisms of nutrition (trophic levels), the other being autotrophs (auto = self, troph = nutrition). Autotrophs use energy from sunlight (photoautotrophs) or oxidation of inorganic compounds (lithoautotrophs) to convert inorganic carbon dioxide to organic carbon compounds and energy to sustain their life. Comparing the two in basic terms, heterotrophs (such as animals) eat either autotrophs (such as plants) or other heterotrophs, or both.

Detritivores are heterotrophs which obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces).[7] Saprotrophs (also called lysotrophs) are chemoheterotrophs that use extracellular digestion in processing decayed organic matter. The process is most often facilitated through the active transport of such materials through endocytosis within the internal mycelium and its constituent hyphae.[8]

  1. ^ "heterotroph". Dictionary.com Unabridged (Online). n.d.
  2. ^ "heterotroph". Merriam-Webster.com Dictionary. Merriam-Webster.
  3. ^ "Heterotroph Definition". Biology Dictionary. April 28, 2017. Retrieved 2023-12-02.
  4. ^ Hogg, Stuart (2013). Essential Microbiology (2nd ed.). Wiley-Blackwell. p. 86. ISBN 978-1-119-97890-9.
  5. ^ "How Cells Harvest Energy" (PDF). McGraw-Hill Higher Education. Archived from the original (PDF) on 2012-07-31. Retrieved 2010-10-10.
  6. ^ Lwoff, A.; C.B. van Niel; P.J. Ryan; E.L. Tatum (1946). Nomenclature of nutritional types of microorganisms (PDF). Cold Spring Harbor Symposia on Quantitative Biology. Vol. XI (5th ed.). Cold Spring Harbor, N.Y.: The Biological Laboratory. pp. 302–303. Archived (PDF) from the original on 2017-11-07.
  7. ^ Wetzel, R.G. (2001). Limnology: Lake and river ecosystems (3rd ed.). Academic Press. p. 700.
  8. ^ "The purpose of saprotrophs and their internal nutrition, as well as the main two types of fungi that are most often referred to, as well as describes, visually, the process of saprotrophic nutrition through a diagram of hyphae, referring to the Rhizobium on damp, stale whole-meal bread or rotting fruit." Advanced Biology Principles, p 296.[full citation needed]