Photosynthesis
Animals and plants both synthesize fats and proteins from carbohydrates; thus glucose is a basic energy source for all living organisms. The oxygen released, with water vapour in transpiration, as a photosynthetic by-product, principally of phytoplankton, provides most of the atmospheric oxygen vital to respiration in plants and animals, and animals in turn produce carbon dioxide necessary to plants. Photosynthesis can therefore be considered the ultimate source of life for nearly all plants and animals by providing the source of energy that drives all their metabolic processes. The discovery of photosynthesis in cells began with the findings of Joseph Priestly. Joseph Priestly, a chemist and minister, discovered that when he isolated a volume of air under an inverted jar, and burned a candle in it, the candle would burn out very quickly, much before it ran out of wax. He further discovered that a mouse could similarly “injure” air. He then showed that the air that had been “injured” by the candle and the mouse could be restored by a plant. In 1778, Jan Ingenhousz, court physician to the Austrian Empress, repeated Priestley’s experiments.
