Without an atmosphere, the Earth would be a rocky planet with no oceans, clouds or life. The mix of gases and conditions in the Earth's atmosphere make life possible. Plants and animals need the gases in the air to survive, and the protection the atmosphere provides helps sustain life as well.
The atmosphere contains a large amount of nitrogen. Some plants take nitrogen straight from the air and use it to build nutrients needed for growth. Atmospheric wind erodes land so it can be broken down to form life-sustaining soil.
