Final answer:
During photosynthesis, oxygen gas is produced as a waste product originating from water molecules. The process uses sunlight, carbon dioxide, and water to generate energy-storing carbohydrates and release oxygen. This oxygen is vital for animals to survive.
Step-by-step explanation:
During photosynthesis, oxygen gas is produced as a waste product. It originates from the oxygen atoms contained in water molecules. In the process of photosynthesis, sunlight, carbon dioxide, and water are used to produce energy-storing carbohydrates, and oxygen is generated as a byproduct. This oxygen is released into the atmosphere through the stomata of plant cells, providing the necessary oxygen for animals to live.