Decomposers are organisms that break down organic matter and release the nutrients into the environment around them. Decomposition is a chemical process similar to digestion, and many sources use the words digestion and decomposition interchangeably.[1] In both processes, complex molecules are chemically broken down by enzymes into simpler, smaller ones. The term "digestion," however, is most commonly used to refer to food breakdown that occurs within animal bodies, and results in the absorption of nutrients from the gut into the animal's bloodstream.[2] Decomposition happens outside of an organism's body, in the environment. Decomposition is also referred to as external digestion; the decomposer works not by swallowing the dead tissue and then digesting it, but by releasing enzymes directly onto it.[3] After allowing the enzymes time to digest the material, the decomposer then absorbs the nutrients released by the chemical reaction into its cells.
The ability to perform external digestion is only possessed by certain groups of organisms, such as bacteria and fungi.[4] Like herbivores and predators, decomposers are heterotrophic, meaning that they must consume organic matter in the form of other organisms to get carbon and nutrients for growth and development. While the terms decomposer and detritivore are often used interchangeably, detritivores digest dead matter internally using enzymes in their guts, while decomposers release digestive enzymes onto the dead material and then absorb the nutrients directly through their bodies' surfaces.[5][6] Thus, invertebrates such as earthworms, woodlice, and sea cucumbers are technically detritivores, not decomposers, since they must ingest their food before digesting it internally and then absorbing through the wall of the gut.[7]
Fungi
editThe primary decomposer of litter in many ecosystems is fungi.[8][9] Unlike bacteria, which are unicellular organisms and are decomposers as well, most saprotrophic fungi grow as a branching network of hyphae. While bacteria are restricted to growing and feeding on the exposed surfaces of organic matter, fungi can use their hyphae to penetrate larger pieces of organic matter below the surface. Additionally, only wood-decay fungi have evolved the enzymes necessary to decompose lignin, a chemically complex substance found in wood.[10] These two factors make fungi the primary decomposers in forests, where litter has high concentrations of lignin and often occurs in large pieces. Fungi decompose organic matter by releasing enzymes to break down the decaying material, after which they absorb the nutrients in the decaying material.[11] Hyphae are used to break down matter and absorb nutrients and are also used in reproduction. When two compatible fungi hyphae grow close to each other, they will then fuse for reproduction and form another fungus.[11]
See also
editReferences
edit- ^ Clark, Mary Ann; Douglas, Matthew; Choi, Jung (2018-03-28). "6.1 Energy and Metabolism - Biology 2e | OpenStax". openstax.org. Retrieved 2024-10-30.
- ^ Patricia, Justin J.; Dhamoon, Amit S. (2024), "Physiology, Digestion", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 31334962, retrieved 2024-10-30
- ^ "31.2: Fungal Forms, Nutrition, and Reproduction". Biology LibreTexts. 2021-12-05. Retrieved 2024-10-30.
- ^ "NOAA. ACE Basin National Estuarine Research Reserve: Decomposers". Archived from the original on 2014-10-09. Retrieved 2012-09-17.
- ^ Griffiths, Hannah M.; Ashton, Louise A.; Parr, Catherine L.; Eggleton, Paul (September 2021). "The impact of invertebrate decomposers on plants and soil". New Phytologist. 231 (6): 2142–2149. doi:10.1111/nph.17553. hdl:10072/406155. ISSN 0028-646X.
- ^ Trophic level. Eds. M. McGinley & C. J. Cleveland. Encyclopedia of Earth. National Council for Science and the Environment. Washington DC
- ^ "Decomposers". citadel.sjfc.edu. Archived from the original on 2019-06-26. Retrieved 2019-05-09.
- ^ Godbold, Douglas L.; Hoosbeek, Marcel R.; Lukac, Martin; Cotrufo, M. Francesca; Janssens, Ivan A.; Ceulemans, Reinhart; Polle, Andrea; Velthorst, Eef J.; Scarascia-Mugnozza, Giuseppe; De Angelis, Paolo; Miglietta, Franco (2006-03-01). "Mycorrhizal Hyphal Turnover as a Dominant Process for Carbon Input into Soil Organic Matter". Plant and Soil. 281 (1): 15–24. doi:10.1007/s11104-005-3701-6. ISSN 1573-5036. S2CID 24926892.
- ^ Talbot, J. M.; Allison, S. D.; Treseder, K. K. (2008). "Decomposers in disguise: mycorrhizal fungi as regulators of soil C dynamics in ecosystems under global change". Functional Ecology. 22 (6): 955–963. doi:10.1111/j.1365-2435.2008.01402.x. ISSN 1365-2435.
- ^ Blanchette, Robert (September 1991). "Delignification by Wood-Decay Fungi". Annual Review of Phytopathology. 29: 281–403. doi:10.1146/annurev.py.29.090191.002121.
- ^ a b Waggoner, Ben; Speer, Brian. "Fungi: Life History and Ecology". Introduction to the Funge=24 January 2014.
Further reading
edit- Bear, MH; Hendrix, PF; Cheng, W (1992). "Microbial and faunal interactions and effects on litter nitrogen and decomposition in agroecosystems". Ecological Monographs. 62 (4): 569–591. doi:10.2307/2937317. JSTOR 2937317. S2CID 86031411.
- Hunt HW, Coleman DC, Ingham ER, Ingham RE, Elliot ET, Moore JC, Rose SL, Reid CPP, Morley CR (1987) "The detrital food web in a shortgrass prairie". Biology and Fertility of Soils 3: 57-68
- Smith TM, Smith RL (2006) Elements of Ecology. Sixth edition. Benjamin Cummings, San Francisco, CA.