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All of them feed on dead and decaying matter (detritus). Detrivores and decomposers are distinct, as it says on Wikipedia, in the fact detrivores consume macroscopic clumps of detritus while decomposers metabolise detritus on a microscopic scale. Are detrivores and decomposers both types of saprotrophs? Also, what exactly does the term "saprozoic" mean, and how is it distinct from saprotroph and decomposer?

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Detritivores consume (eat) detritus.

Saprotrophs feed on dead organic matter by the means of extracellular digestion.

Saprozoic organisms are protozoans that are saprotrophs. This actually comes from an obsolete classification of plants and animals where bacteria and fungi were grouped with plants and were therefore called saprophytes if they are saprotrophic. Protozoans were considered animals; so saprozoic.

Decomposer is a broad class including both detritivores and saprotrophs.

Scavengers also consume dead organisms. They are distinct from detritivores because the former consumes a relatively larger amount of dead matter. Often, scavengers are the first to consume dead organisms; the leftovers are processed by decomposers.


I could not find any authoritative source for these definitions. A peer-reviewed article by Getz (2010) attempts to classify organisms based on their eating habits.

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  • $\begingroup$ How do we define decomposes then? The definition that I have come by mostly is that they are organisms that break down complex organic molecules into simpler ones, in heterotrophs at any level digestion does the same. So why a new term 'decomposers'? (I'm definitely missing out something). $\endgroup$ – Tyto alba Mar 18 '17 at 21:14
  • $\begingroup$ Also scavengers? They too eat dead organisms(part of detritus)? $\endgroup$ – Tyto alba Mar 18 '17 at 21:15
  • $\begingroup$ @SanjuktaGhosh Decomposers is a very general term and can be considered as a colloquial term. As I mentioned in the answer these organisms enable breakdown of the dead matter. Of course they are heterotrophs but they are different from other kind of heterotrophic interactions such as predation and parasitism. Other heterotrophs are not very efficient at turning over a large mass of organic matter like the decomposers. $\endgroup$ – WYSIWYG Mar 20 '17 at 6:12
  • $\begingroup$ I tried to find out what do human beings excrete, as obvious the excreta is rich is macromolecules(undigested). I read somewhere that the 'excreta' of microbes is rather formed of inorganic molecules (something that can directly be absorbed by plants?- is this what makes this group of heterotrophs decomposers?) $\endgroup$ – Tyto alba Mar 20 '17 at 9:43
  • $\begingroup$ The bulk of a decomposers diet is non-living organic matter or dead organisms, things that do not fight back in any way. Comparing decomposers and detritivores are like comparing predator and carnivore, they are extrememly close in meaning but one is more focused on how they eat the other on what they eat. $\endgroup$ – John Mar 20 '17 at 14:28
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Decomposers are responsible for the "decay" of dead organisms (carcasses), dropped plant matter, and animal wastes (fecal matter) by externally breaking down the organic material and then absorbing the resulting "nutrients." This typifies the approaches taken by many fungi and bacteria. Detrivores actually feed on or consume decaying material, including the decomposers themselves, and/or other detrivores.

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