Nuclear fission is a process by which the nucleus of an atom is split into two or more smaller nuclei, known as fission products. The fission of heavy elements is an exothermic reaction, and huge amounts of energy are released in the process.
Photosynthesis is the process where plants create energy. It requires water, carbon dioxide and sunlight. The end result is glucose, which the plants consume, and oxygen. Cellular respiration requires oxygen and glucose. The end result is carbon dioxide, ATP, and water.