The primary source of oxygen produced by photosynthesis is derived from water (H2O). During photosynthesis, plants, algae, and some bacteria utilize sunlight to convert carbon dioxide and water into glucose and oxygen. The process occurs in chloroplasts where light energy splits water molecules, releasing oxygen as a byproduct. This oxygen is essential for the survival of aerobic organisms on Earth. Photosynthesis not only contributes to the oxygen supply but also forms the foundation of the food chain by producing organic energy sources.