1. Carbon dioxide diffuses from the atmosphere or water into autotrophs

2. In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions

3. Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds

4. Carbon dioxide is produced by respiration and diffuse out of organisms into water or the atmosphere

5. Methane is produced from organic matter in anaerobic conditions by methanogenic archaea and some diffuses into the atmosphere or accumulates in the ground

6. Methane is oxidized to carbon dioxide and water in the atmosphere

7. Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils

8. Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in porous rocks

9. Carbon dioxide is produced by combustion of biomass and fossilized organic matter

10. Animals such as reef-building corals and Mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone

1. Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds

2. Estimation of carbon fluxes due to processes in the carbon cycle (in gigatonnes)

1. Construct a diagram of the carbon cycle

2. Making accurate, quantitative measurements-it is important to obtain reliable data on the concentrations of carbon dioxide and methane in the atmosphere