Human beings require air because, like all other animals, they are aerobic organisms who require oxygen, which is a component of air. While oxygen is found in water, humans evolved to extract the oxygen from air, as birds, mammals and reptiles do, instead of from the water, as fish and some amphibians do. Additionally, air is necessary to keep the planet warm as it insulates the planet like a blanket.
The Earth’s air is composed primarily of nitrogen, which is a noble gas that is not very reactive. The nitrogen in the air does not provide any resources for humans, but it does help plants to survive, which in turn helps humans to survive. About 78 percent of the atmosphere by volume is composed of nitrogen. About 21 percent of the remaining 22 percent is comprised of oxygen. The final 1 percent of the air is made of argon, carbon dioxide and other minor components.
Oxygen is the primary chemical necessary for oxidative respiration, which is the process by which aerobic cells derive their energy. Additionally, without an atmosphere of air, the world would not retain much of the sun’s heat. The earth would be a much cooler and less hospitable place without an atmosphere.