If we think of a blanket, it covers us, protects us from the cold and other elements.
And if we think of the atmosphere, WE (humans, animals, trees, fungi--- everything that's in our world) are covered by different layers of it. They protect us from UV rays, cold temperature of space, etc.
However, we often overuse blankets and it rips. The same thing happen with our atmosphere, particularly the ozone layer. We have released too much toxic gases and CFCs that it developed holes in areas. If the holes continue to expand, we would be vulnerable to the dangerous elements. That could spell the end for the human race...
Hope this helps... :D