1) Oxygen, which is required for the survival of every living organisms is present in the atmosphere.
2) atmosphere works as an insulator, it keeps the average temperature of the earth fairly constant during the day and night by preventing escape of heat into outer space.
3) atmosphere is also act as protective blanket for the earth. it observes most of the harm full radiations such as ultraviolet ( uv ) radiations coming from the sun. it results in the earth receiving just the right amount of heat and sun's rays, which helps in the climate control and allow the living organisms to exist.
4) it contain all the gases which are essential for sustaining life on the earth.
5) water cycle is not possible without atmosphere.