The decomposer, also known as the "restorer", is heterotrophs. Refers to bacteria, fungi and other organisms with decomposition ability in the ecosystem, including some protozoa and small invertebrates, heterotrophs. They can decompose complex organic matter in animal and plant residues into simple organic matter and release it into the environment for reuse by producers, contrary to producers.

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.