Atmosphere acts as a protective blanket for the organisms to exist:
a) It acts as a barrier for the harmful ultraviolet radiations from reaching the surface of the earth.
b) It keeps the average temperature of the earth fairly constant during daytime and even during the course of the whole year.
c) During the daytime, it prevents the sudden increase in the temperature.
d) At night time it slows down the escape of heat from the surface of the earth.