The major useful component of the atmosphere is

The major useful component of the atmosphere is oxygen. Oxygen makes up about 21% of the air we breathe, and it is essential for the survival of most living organisms, including humans. Oxygen is used by our bodies to break down food and release energy, a process known as cellular respiration. It is also important for combustion, which is the process of burning fuel to produce heat and energy. In addition, oxygen is involved in the formation of ozone, which is a protective layer in the upper atmosphere that helps to absorb harmful ultraviolet radiation from the sun. Without oxygen, life as we know it would not be possible on Earth.