ABSTRACT
All life on earth depends on the continuous acquisition of energy. The sun provides nearly all earth’s renewable energy in the form of radiation. Radiant energy heats the earth, causing convection and contributing in great measure to weather patterns, which transfer water through the atmosphere from oceans and lakes to land and back; this creates the basic environment needed to nurture life. However, life itself depends on the availability of chemical energy, the vast majority of which also is captured from sunlight. Plants with chlorophyll perform the function of energy capture, utilizing photons to drive the cleavage of water into oxygen and hydrogen. In the reaction termed photosynthesis, carbon dioxide (some of which is created by the respiration of plants, animals, fungi, and bacteria) is ultimately recycled by its conversion into oxygen, water, and sugar. The chemical energy of sugar is then used to drive all of the other metabolic reactions needed to perpetuate life. The carbon in sugar is utilized to produce all of the more complex carbohydrates, proteins, and other structural molecules that make up plant cells, tissues, and organs. In turn, the chemical energy and nutritive substances contained in plants are used as the primary energy source for animals.
