Decomposer Decomposer is an organism that transforms the organic matter contained in animal and plant residues and animal excretory relics into simple inorganic matter in the ecosystem. It mainly includes saprophytic bacteria and fungi, protozoa, small invertebrates and other heterotrophs.
The role of decomposers in ecosystems is extremely important. Without decomposers, animal and plant residues and excreta cannot be recycled, substances will be locked in organic matter and cannot be used by producers, the material cycle of the ecosystem will end and the whole ecosystem will collapse. The role of decomposer can't be accomplished by one organism, and different organisms are needed at different stages.