All ecosystems contain three basic types of organisms: producers, consumers and decomposers. Each type of organism plays a vital role in the ecosystem. If one of the three types of organisms were to disappear, all living things would die as the cyclical flow of life-giving energy collapsed.
An ecosystem is a network of living organisms and non-living things. The organisms in an ecosystem rely on each other and their environment to sustain themselves. An ecosystem may be any size, from a part of your home to regions larger than most nations. Different environments have their own unique ecosystems, but there is no such thing as a single, perfect environment. Organisms develop within a given environment and will adapt or perish as the environment changes.
Although the three types of organisms work together in a cycle of energy, it is easiest to think of producers as the organisms that begin the cycle. Producers take energy from inorganic sources and convert it into sugars. Green plants are producers that take energy from the sun and create sugars through photosynthesis. Deep-sea bacteria are also producers; they live near vents in the ocean's floor and convert chemicals into sugar. Producers are autotrophs because they are at the base of the food chain (also known as trophic levels).
As their name suggests, consumers are the organisms that consume energy from producers. Insects and animals are consumers, and there are three types within this category. Herbivores are primary consumers because they eat only autotrophs (plants). Carnivores then consume these herbivores (insects and animals). If a carnivore only eats herbivores, it is a secondary consumer. A carnivore that eats the secondary consumer would be a tertiary consumer. Omnivores, such as humans, consume both autotrophs and herbivores (and occasionally carnivores).
Decomposers are the final type of organism in an ecosystem. All producers and consumers eventually die and become detritus. The decomposers then consume this lifeless detritus and convert it into vital inorganic material. Decomposers return this inorganic material to the environment where it provides important nutrients for producers. Thus, the cycle begins again as nutrients provided by decomposers sustain producers, consumers feed on the producers and decomposers reintroduce the remaining energy.