Decomposer

From Wikipedia, the free encyclopedia

For the Matches album of the same name, see Decomposer (album).

The fungi on this tree are decomposers.

Decomposers (or saprotrophs) are organisms that consume dead organisms, and, in doing so, carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. Decomposers use deceased organisms and non-living organic compounds as their food source. The primary decomposers are bacteria and fungi.

[hide]

[edit] Importance of decomposers in the ecosystem

When a plant or animal dies, it leaves behind nutrients and energy in the organic material that comprised its body. Scavengers and detritivores can feed on the carcasses, but they will inevitably leave behind a considerable amount of unused energy and nutrients. Unused energy and nutrients will be present both in the unconsumed portions (bones, feathers or fur in the case of animals, wood and other indigestable litter in the case of plants) and in the feces of the scavengers and detritivores. Decomposers eat things by breaking down this remaining organic matter by breaking it into pieces. Decomposers eventually convert all organic matter into carbon dioxide (which they respire) and nutrients. This releases raw nutrients (such as nitrogen, phosphorus, and magnesium) in a form usable to plants and algae, which incorporate the chemicals into their own cells. This process resupplies nutrients to the ecosystem, in turn allowing for greater primary production.

Although decomposers are generally located on the bottom of ecosystem diagrams such as food chains, food webs, and energy pyramids, decomposers in the biosphere are crucial to the environment. By breaking down dead material, they provide the nutrients that other organisms need to survive. As decomposers feed on dead organisms, they leave behind nutrients. These nutrients then become part of the soil. Therefore, more plants can grow and thrive.

[edit] Bacteria

Bacteria are the primary decomposers of dead animals (carrion) and are the primary decomposers of dead plant matter (litter) in some ecosystems. In soils, active fungal hyphae and bacteria are much more important in the recycling of nutrients. Bacteria can also be very important in agricultural fields, because tillage usually increases the abundance of bacteria relative to fungi.

[edit] Fungi

Fungi are the primary decomposers of litter in many ecosystems. Unlike bacteria, which are unicellular, 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. Additionally, only fungi have evolved the enzymes necessary to decompose lignin, a chemically complex substance found in wood. These two factors make fungi the primary decomposers in forests, where litter has high concentrations of lignin and is often in large pieces. Also, if manufactured with other organisms, may grow elsewhere from its chemical pursuit, leaving behind the same type of bacteria left on the plant, tree organism, etc.

[edit] Decomposers and detritivores

Some animals, like millipedes and woodlice, are commonly called decomposers, because such animals consume dead organic matter and contribute to the process of decomposition. Scientists, however, refer to such organisms as detritivores. This distinction is made because bacteria and fungi are capable of digesting many complex chemical molecules that animals are incapable of digesting. Additionally, bacteria and fungi digest and decompose organic matter more fully than detritivores, reducing it to inorganic material. For these reasons, bacteria and fungi play a more fundamental role in the processes of decomposition and nutrient recycling than animals. There are a lot of other kinds of detritivores around the world, including slugs and worms.

[edit] References

This article includes a list of references or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations where appropriate. (February 2008)

Beare MH, Parmelee RW, Hendrix PF, Cheng W (1992) Microbial and faunal interactions and effects on litter nitrogen and decomposition in agroecosystems. Ecological Monographs 62: 569-591

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.

Swift MJ, Heal OW, Anderson JM (1979) Decomposition in Terrestrial Ecosystems. University of California Press, Berkeley, CA.

Feeding behaviour of Animals

Carnivores

adult	Hematophagy · Insectivore · Myrmecophagy · Lepidophagy · Man-eater · Molluscivore · Mucophagy · Ophiophagy · Piscivore · Spongivore

reproductive	Oophagy · Ovophagy · Paedophagy · Placentophagy

cannibalistic	Autophagy · Cannibalism · Human cannibalism · Self-cannibalism · Sexual cannibalism