The term anaerobic refers to living processes (usually the release of energy from nutrients) that take place in the absence of oxygen. Some prokaryotic bacteria, live in the atmosphere where there is no oxygen available and therefore gets energy from organic compounds without oxygen. Most organisms alive today extract their energy from nutrients aerobically (in the presence of oxygen). Aerobic respiration releases a lot of energy from nutrients, while Anaerobic respiration releases only a little bit of energy.