All of the living things that are part of the ecosystem has something to do with the whole process. If one of them would be removed, the process will not be complete. In this case, the decomposers are in charge of breaking down the dead organisms and making them a part of the soil.
The soil will then be richer and will be able to produce plants that will be consumed by living things. Some examples of decomposers are fungi, snails, and certain insects. The decomposers usually make it a point to break down dead things but they also have the tendency to feast in living things that are still alive.