An ecosystem (or ecological
system) consists of all the organisms and the physical environment with which they interact. 458 These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into
plant tissue. By feeding on plants and on one another, animals
play an important role in the movement of matter and energy through the system. They also influence the quantity of
plant and microbial biomass present. By breaking down dead
organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and microbes.