Nutrients and energy are passed on in cycles in almost all ecosystems. Producers are the organisms that produce biomass. These are mainly plants and bacteria. Consumers consume this biomass and are dependent energy-wise on the producers. Consumers are mainly humans and animals. Decomposers are the creatures in the producer-consumer-decomposer cycle that are responsible for breaking down dead organic matter. They convert these into simple organic compounds and thus make them accessible to other living beings again. Most often, these are microorganisms such as bacteria and fungi.