At the most basic level, energy is stored in chemical bonds. Plants Plants are able to directly absorb energy from the sunlight, and store it in chemical bonds. Later, when the plant needs the energy to grow, it can break the C 6 H 12 O 6 molecule apart to release it. Actually, the light energy is used to break water down into hydrogen and oxygen. These further reactions constitute the Calvin cycle, which can take place in the dark using the stored energy.
Photosynthesis releases oxygen as a by-product.
During the early stages of cellular life on Earth, bacteria changed the make-up of the atmosphere by releasing oxygen. Animals Animals gain energy by eating plants or other animals, gaining energy in two ways. First, animals can break the organic molecules in plants down into smaller parts much like the plants would, to release the energy stored there. Second, animal s metabolism makes use of the now-abundant oxygen in the atmosphere, to break the organic molecules of plants all the way back down into water and carbon dioxide. Bacteria have been found living under the Antarctic ice, living near undersea volcanic vents, or living in rocks.