There are two possible answers for this question: detritivores or decomposers. These are heterotrophs that obtain nutrients by feeding on decomposing plant and animal parts and also animal waste. Many plants, invertebrates and vertebrates are detritivores, and they help to cycle nutrients in the ecosystem. These are however not species that digest matter on a molecular scale such as bacteria, fungi and protists, as detritivores ingest discrete lumps of matter.