Role of decomposer in fooe chain/food web Decomposers are organisms which convert complex organic molecules into their simple forms. Example bacteria, fungi etc. Explanation food chain stary from autotrophs and end at decomposers. these organisms are present in soil, rely on dead bodies of plants and animals for their nutrient requirements. These organisms possess strong enzymatic system, which scavenge comples molecules from dead bodies during respiration and convert them into simple nutrients which return back to atmosphere.