The importance of atmosphere of the earth are:-
#=># The presence of the atmosphere plays a significant role in the water cycle. It facilitates the formation of clouds which remains suspended until they are heavy enough to pour down on the earth as rain,hail or snow.
#=>#Protects the life forms of the earth from the harmful UV rays of the sun.The presence of the ozone layer does this by reflecting the UV rays of the sun.
#=># It keeps the temperature of the earth constant so that it is suitable to support life.
#=># It protects the earth from smaller meteors.
#=># Contains #N_2# ,#O_2# and other gases which are necessary to support the life form on the earth.
#=>#Facilitates combustion and without the atmosphere combustion is not possible.
Here is the structure of the atmosphere:-