Photosynthesis, the process by which green plants capture the sun's rays, is a complex process, but one that is essential for
the continuance of life on earth. In essence, photosynthesis uses the energy in light to change water and carbon dioxide into glucose (a simple sugar), with oxygen - a gas that humans and other animals need in order to breathe - as a by-product.
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Photosynthesis has other important results besides the release of oxygen into the atmosphere. For example, animals and humans need glucose for energy, but they are unable produce it themselves. So they depend on the plants they eat to produce it for them. Fossil fuels are also an ancient product of photosynthesis, and humans depend on them to run their cars and heat their homes. So without photosynthesis, the world would be a very different place!