Organisms that rely directly on inorganic material to gain their energy are called
autotrophs, and the major autotrophs in most ecosystems are plants. The beings that rely on autotrophs to in turn to gain these organic nutrients are called
heterotrophs. During the decomposition of any living being, the organic compounds are transferred back into inorganic chemicals, and can be processed again by plants.
Plants also provide the world with much-needed oxygen through a process called
photosynthesis. Life on earth depends on oxygen, and without it, the majority of living things (humans included) would not be able to breathe!