Atmosphere and its composition

The atmosphere is the outer shell of the biosphere, its mass is negligible — only one millionth of the mass of the Earth, but the role in all natural processes is enormous. Availability around the globe of the atmosphere determines the total thermal conditions of the planet's surface and protects it from harmful cosmic rays and ultraviolet radiation from the Sun. Circulation in the atmosphere affects the local climatic conditions and, through them, to the regime of rivers, pocvennorastitel?nyj cover and on relief formation process.
Modern gas composition of the atmosphere is the result of a long historical development of nature. Air, as it is known, is made up of nitrogen (78.09%) and oxygen (20.95 percent), argon (0.93%), and carbon dioxide (0.03%), the neon and other gases and water vapor. in addition, it contains a variety of substances from natural sources: vegetable, as volcanic dust and cosmic origin and occurs when soil erosion, kapel?nozidkuu water (mist), sea-salt particles, gases from the forest and steppe fires, various products of vegetable, animal or microbiological origin.
The lower prevailing rate, part of the atmosphere is called the troposphere. It stretches up to the heights of 8-10 km in the polar latitudes, up to 10-12 km is in moderation, up to 16-20 — in the rain. Above the troposphere is the stratosphere, troposphere is separated from the relatively thin transitional layer-tropopauzoj. In the stratosphere the proportion of nitrogen and oxygen decreases and increases the percentage of hydrogen, helium and other gases. It is between the troposphere and the stratosphere is the ozone layer, which absorbs most of the ultraviolet solar radiation, protecting wildlife on the planet.
Above the stratosphere, continuing up to the height of 55-95 km, stretches the ionosphere (around 1000 km altitude). This layer can reflect radio waves, allowing distant radio communication across the globe (this phenomenon is the presence here of positive and negative ions and free electrons). And finally, the ionosphere is the exosphere is a leakage of light gases of the atmosphere into space.
For human life is the most important part of the air is oxygen. Through the light it enters the blood, which delivers it together with nutrients in the cells of the body. When you join the oxygen with carbon is the initial energy stimulating the muscles, warming the body that provides the nervous system, the brain, the metabolism (i.e. Exchange) processes.