There is a troposphere which hold most oxygen, carbon dioxide, and other things. The Earth's atmosphere has all of those things which keep it under control. :)
Edit : Here's 4 things: 1) Oxygen, which many living things need.
2) Water which gives rain. Water is essential to life as we know it and rain helps to distribute water.
3) Ozone layer reduces harmful radiation from the Sun.
4) Natural "greenhouse effect" keeps the planet's average temperature above the freezing point of water.
It does not. Or perhaps I should say, you have the causal direction wrong. Life as we know it evolved here, on Earth, under Earth conditions. It's not a miracle that Earthly life developed under Earthly conditions; we could hardly expect Earth-type life to develop on alien planets, or alien life to develop here. We mould our environment, and our environment moulds us.
If we look at other planets or other locations, we're likely to discover totally different and alien kinds of life that evolved THERE, suited to THOSE conditions.
the atmosphere contains oxygen and other gases that you and other living things need to survive.
more radiation ; bad living conditions for the people of earth
A the answer is hydrogen
The earth's atmosphere is what we must breath or we would suffocate and die.
Not without a suitably engineered habitat designed to mimic the conditions here on Earth.
Biosphere.
you can't exactly kill Earth's atmosphere because it isn't living, but things like CFCS (chlorofluorocarbons) can damage it
The ozone layer
The formation of the ozone hole is affecting the living things. The hole in ozone is causing UV to enter and affecting the humans.
more radiation ; bad living conditions for the people of earth
Ozone holes makes room for UV rays. These are fatal for life on earth.
Earth has liquid water and suitable temperature range and atmosphere for living things to survive. Your Welcome People!
At the moment, no planets are known to have conditions similar to Earth's for supporting life. If there planets similar to Earth, there would definitely be living organisms of some sort. On the other hand, there is slightly less chance of sentinent life such as our own species existing.