(2) Oxygen Explanation: In plants, algae, and cyanobacteria, photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth. In oxygenic photosynthesis water is the electron donor and, since its hydrolysis releases oxygen, the equation for this process is: Carbon dioxide + Water + Light energy --> Carbohydrate + Oxygen + Water