G. Carbon dioxide and water vapor are very significant energetically, because they absorb many wavelengths of earth, or terrestrial radiation. H. Ozone is very significant energetically, because it absorbs harmful ultraviolet radiation. Most of it accumulated from volcanic eruptions over eons. The level of oxygen was very small until about 400-600 million years ago. Photosynthesis - the primary energy capturing device in the biosphere.
Green plants can convert solar energy to chemical energy.
O 2 b. Carbohydrates are the energy base of most living things. Plants and animals consume food, combine it with oxygen we breath to reverse photosynthesis. We call this respiration. It is the source of our metabolic energy. It also, as a byproduct, has allowed molecular oxygen to accumulate in the atmosphere.