Carbon moves from one storage reservoir to another through a variety of mechanisms. For example, in the food chain, plants move carbon from the atmosphere into the biosphere through photosynthesis. ... Respiration, excretion, and decomposition release the carbon back into the atmosphere or soil, continuing the cycle. Carbon dioxide is absorbed from the atmosphere by plants and algae and converted to carbohydrates by photosynthesis. Carbon is then passed into the food chain and returned to the atmosphere by the respiration and decay of animals, plants, and other organisms.