Which gas found in air is essential to sustain life?

Oxygen is the gas found in the air that is essential to sustain life. It plays a critical role in the process of respiration for aerobic organisms, which includes humans, animals, and many other living beings. During respiration, oxygen is taken into the body and used to convert food into energy, producing carbon dioxide as a byproduct that is then expelled.

Without oxygen, these organisms would be unable to produce the energy necessary for bodily functions, leading to cell death and ultimately the failure of vital organs. While nitrogen is abundant in the atmosphere and serves various purposes, including diluting oxygen and preventing combustion, it is not utilized by the body in the same way. Hydrogen is a component of water and organic molecules but is not found in a free gaseous state in the atmosphere. Ozone, while important in the upper atmosphere for blocking harmful UV radiation, is not used in metabolic processes by living organisms. Thus, oxygen stands out as essential for life itself.