Photosynthesis is the ultimate source of the energy for all the food that humans require, as well as the source of the energy used to build the biological materials that humans use, such as wood, cotton and wool. It is also the major source of oxygen gas that all animals require.
Photosynthesis is the conversion of carbon dioxide and water into carbohydrates using energy from sunlight. It is the main process by which new energy becomes available to life on Earth. Plants and algae use photosynthesis to convert light energy into a form available to other organisms, and thus form the base of almost every food chain. Animal materials and foods can also be traced back to this source of energy and materials.
Beyond the immediate energy and materials that photosynthesis provides, it is also the source of the energy stored in fossil fuels, which come from the decomposition of buried organisms without oxygen. These decayed remains are subjected to geological processes, such as heat and pressure, for millions of years to become coal, oil and natural gas. These together make up over 85 percent of humans' energy use. Photosynthesis is also an important factor in reducing the damage many scientists worry about due to carbon dioxide levels.