The difference between aerobic and anaerobic respiration lies primarily in the presence or absence of oxygen. Aerobic respiration occurs in the presence of oxygen and efficiently produces energy, yielding up to 36 ATP molecules from one glucose molecule. This process takes place in the mitochondria and involves the complete oxidation of glucose. In contrast, anaerobic respiration occurs in low-oxygen environments and produces less energy, typically yielding only 2 ATP molecules, while generating byproducts like lactic acid or ethanol. These metabolic pathways have implications for organisms’ survival in various environments.