Autotrophs and heterotrophs are the two groups of living organisms as classified by their food source. Here is a look at the difference between autotrophs and heterotrophs, with examples of organisms.
Autotroph vs Heterotroph Summary
Autotrophs and heterotrophs differ according to their nutrition.
| Autotrophs | Heterotrophs |
|---|---|
| Make their own food | Do not produce their own food |
| Producers | Consumers |
| Make food from inorganic compounds | Get food by eating autotrophs or heterotrophs |
| Primary level of a food chain | Secondary and tertiary levels of a food chain |
| Plants, algae, some bacteria, archaea | Animals, fungi, some protists, some bacteria |
Autotrophs
An autotroph is an organism that makes complex organic compounds from simple carbon compounds, such as carbon dioxide. Photoautotrophs use light as an energy source, while chemoautotrophs use inorganic chemical reactions as an energy source. Autotrophs are primary producers.
Examples of autotrophs include:
- Most plants
- Algae
- Some bacteria
- Phytoplankton (although sometimes phytoplankton is a mixotroph)
Heterotrophs
A heterotroph is an organism that gets nutrition from autotrophs or other heterotrophs. For example, a cow (heterotroph) eats grass (autotroph). Humans (heterotrophs) eat plants (autotrophs) and animals (heterotrophs). Fungi (a type of heterotroph called a saprotroph) absorbs nutrients from other decaying organisms. Heterotrophs are consumers.
Examples of heterotrophs include:
- All animals, including humans
- Fungi
- Most protozoa
- Most bacteria
- Some scientists include parasitic plants, while others group them with mixotrophs.
- Some scientists include lichens, while others call them mixotrophs.
Heterotrophs may be chemoheterotrophs or photoheterotrophs. A chemoheterotroph is incapable of carbon fixation, so it obtains some organic compounds from other sources. Humans and most animals, fungi, and halophilic bacteria are chemoheterotrophs. Photoheterotrophs use light as an energy source, but they cannot use carbon dioxide as a sole carbon source and must get organic compounds from their environment. Examples of photoheterotrophs include some aphids, the oriental hornet, heliobacteria, purple non-sulfur bacteria, and green non-sulfur bacteria.
Learn about the kingdoms of life in biology and get examples of organisms.
Mixotrophs
Some organisms use a mixture of energy and carbon sources, so they are not strictly autotrophs or heterotrophs. These organisms are mixotrophs. Some mixotrophs switch between autotrophy and heterotrophy, depending on resource availability. Others routinely make their own food while consuming other organisms. So, mixotrophy may be obligate or facultative. An obligate mixotroph must use both autotrophy and heterotrophy, while a facultative mixotroph adjusts its strategy in response to environmental conditions.
Here are examples of mixotrophs:
- Most plankton are mixotrophs.
- Parasite and carnivorous plants, such as the Venus flytrap are mixotrophs.
- The embryo of spotted salamander has microalgae in its cells.
- The green algae Chlorella lives symbiotically within cells of some freshwater and marine protozoa and invertebrates.
- Some corals, jellyfish, and anemones host microsymbiotic algae within their cells.
- Some bacteria switch between being chemoheterotrophs and chemolithoautotrophs.
- Lichens possess the autotrophic properties of algae and the heterotrophic qualities of fungi.
References
- Eiler, A. (December 2006). “Evidence for the Ubiquity of Mixotrophic Bacteria in the Upper Ocean: Implications and Consequences”. Appl Environ Microbiol. 72 (12): 7431–7. doi:10.1128/AEM.01559-06
- Kirchman, David L. (2014). Processes in Microbial Ecology. Oxford: Oxford University Press. ISBN 9780199586936.
- Liang, Yanna (July 2009). “Biomass and lipid productivities of Chlorella vulgaris under autotrophic, heterotrophic and mixotrophic growth conditions”. Biotechnology Letters. 31 (7): 1043–1049. doi:10.1007/s10529-009-9975-7
- Lwoff, A.; C.B. van Niel; P.J. Ryan; E.L. Tatum (1946). “Nomenclature of Nutritional Types of Microorganisms“. Cold Spring Harbor Symposia on Quantitative Biology. Vol. XI (5th ed.). Cold Spring Harbor, N.Y.: The Biological Laboratory.
- Morris, J.; et al. (2019). Biology: How Life Works (3rd ed.). W. H. Freeman. ISBN 978-1319017637.