Introducing Photosynthesis: What is 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 vapor in transpiration, as a
photosynthetic byproduct, 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.   In 1796, Jean Senebier, a French pastor, showed
that Carbon Dioxide was the "fixed" or "injured" air and that
plants in photosynthesis took it up. Soon afterwards, Theodore
de Saussure showed that the increase in mass of the plant as it
grows could not be due only to uptake of CO2, but also to the
incorporation of water.  Photosynthesis is a process in which
green plants use energy