Where Does Oxygen We Breathe Come From?

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Green plants produce the oxygen that humans and other animals require for life. Plants produce this oxygen via photosynthesis. Photosynthesis is the process by which plants create their own food. Oxygen is a by-product of the process of photosynthesis.

Photosynthesis occurs in green plants that have tiny, cellular structures called chloroplasts. These organelles capture sunlight and harness its energy. Using water, carbon dioxide and nutrients from the air and soil, photosynthetic plants produce sugars and oxygen. The plants vent this oxygen into the air, where animals inhale it to power their metabolisms. The sugars produced in the process hold the energy from the sun, but they convert it to chemical form. Because plants are one of the few organisms that can harness the power of the sun and convert it into food, scientists call green plants “producers.” By contrast, the animals that eat the food produced by the plants are called “consumers.”

Plants and animals produce the gases that the other needs for survival. While plants produce oxygen as a waste product, they use carbon dioxide for respiration. Conversely, animals breathe oxygen and produce carbon dioxide as a waste product. Plants also release a small amount of water during the process of photosynthesis.