- an organism which can photosynthesize (such as a plant or some bacteria) will absorb carbon dioxide (CO2) from the air and incorporate it into its body or turn it into organic matter.
- other organisms which cannot photosynthesize will eat the organic matter, or the photosynthesizing organism, and release CO2 gas as a waste product back into the air.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.