The primary energy source for aerobic organisms is glucose. During aerobic respiration, glucose is metabolized in the presence of oxygen to produce energy, carbon dioxide, and water. This process is highly efficient, yielding approximately 38 ATP molecules per glucose molecule. Aerobic organisms, including humans, rely on this energy to support cellular functions, growth, and activity. The significance of glucose as the primary energy source highlights its role in biological processes and the overall energy economy of ecosystems.