by Radhika Sukram

Created on: May 02, 2009

The earth's atmosphere consists of several layers of gas. They are called the troposphere, stratosphere, mesosphere, ionosphere, and exosphere. The troposphere is the first layer of gas closest to earth. It extends about 10 miles above the earth's surface. Above the troposphere is the stratosphere, which is the ozone layer. The atmosphere is composed of 78% nitrogen, 21% oxygen, 0.038% carbon dioxide and, a small amount of other gases. These gases are upheld by gravity. All life on earth depends on these gases to live and breathe.

Humans and animals utilize oxygen for respiration. Plants use carbon dioxide to produce food by the process of photosynthesis. This creates a balance between humans, plants and animals to live on earth. Plants and animals also need nitrogen to grow healthy. Most fertilizers are made from nitrogen for plants to grow. Animals get nitrogen from eating plant proteins. When plants and animals die, bacteria decompose this organic matter and return nitrogen into the atmosphere. The burning of fossil fuels and vehicle emissions releases a large amount of nitrogen in the atmosphere.

The layer of gas closest to the earth is the troposphere where we live. The main gases found here are water vapor, carbon dioxide, methane, and nitrous oxide. The chemical nature of the atmosphere is what determines the climate. The heat of the sun changes the water from the earth, into water vapor, which rises to the clouds, by the process of evaporation. When the water vapor becomes heavy, condensation takes place and fall as rain to nourish the earth for human, plants and animals to live and grow.

Carbon dioxide from the atmosphere absorbs heat instead of allowing it to escape into space. The heat from the sun can damage crops and kill animals, if they are not prevented from reaching the earth. Carbon dioxide has increased in the air by the burning of coal, oil and natural gas by industrialized countries, and has caused more heat to absorb. Carbon dioxide and methane, deforestation and population are causes for global warming.

The stratosphere is the layer above the troposphere containing the ozone molecules. Ozone absorbs ultraviolet radiation from the sun to protect us from the heat. If there is not enough ozone in the atmosphere, humans will be more exposed to skin cancer, sun burn and heat. Plants and animals will also be affected.

The atmosphere provides nutrients in the form of gases for all forms of life on earth. Without nitrogen, plants cannot get food, and without oxygen humans cannot breathe. The earth will not be able to sustain life, if carbon dioxide does not absorb the radiation from the sun. The earth's atmosphere recycles the water from the earth, which returns for the growth of plants and animals. Not only the atmosphere protects us from the intense heat of the sun, but also the cold frigid vacuum of outer space.

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