lesson 5 - Composition of the Atmosphere In this lesson, we...

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Composition of the Atmosphere In this lesson, we will continue to explore the physical environment so that we can begin to understand how people interact with it. An adequate understanding of the physical environment requires comprehension of the overall character of the atmosphere. The Earth's atmosphere is unique in our solar system because it gives Earth the ability to support life, providing oxygen and carbon dioxide for animal and plant respiration, respectively. In addition, the atmosphere serves as a buffer that shields the Earth from the negative effects of solar radiation. Although the atmosphere is generally invisible, it behaves as a fluid in much the same manner as water, with currents and eddies that affect day-to-day weather. Before you can begin to learn about the behavior of the atmosphere, however, it is essential to grasp the atmosphere's overall composition. The atmosphere contains a variety of elements that can be subdivided into: (1) constant gases ; (2) variable gases ; and (3) impurities . Constant gases Constant gases are those that maintain, more or less, the same proportion on a constant basis. The proportion of these gases in the atmosphere may have changed over very long periods of time (millions of years), but they have maintained the current proportions within more recent history. These gases make up 99% of the atmosphere: Nitrogen – 78% of the atmosphere Oxygen – 21% of the atmosphere Yes, that's right, there is more nitrogen than oxygen in the atmosphere. Our lungs are able to extract enough oxygen from the air we breathe even though oxygen only makes up 21% of that air. Variable gases Variable gases are those that vary in their proportion over time. Although some of these gases are highly significant to life, they make up only a tiny portion of the atmosphere. The most important variable gases are: carbon dioxide water vapor ozone
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Carbon dioxide Carbon dioxide (CO 2 ) is a critical part of the atmosphere for two very important reasons. Initially, plants absorb CO 2 and release oxygen as a by-product. In other words, if plants were not "breathing" in CO 2 , we would have no oxygen for ourselves. Secondarily, CO 2 acts like a blanket over the Earth trapping heat transferred to the atmosphere by the Earth's surface. Fluctuations in carbon dioxide levels in the atmosphere are thought to be a primary component of major climate change. When carbon dioxide levels are low, more heat escapes into space and the Earth cools. When carbon dioxide levels are high, in contrast, more heat is trapped and the Earth warms. Water vapor Water on Earth is found in three states: liquid, solid (ice), and gas (water vapor). In the atmosphere, water vapor is especially vital because it absorbs heat from the Sun. As vapor
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This note was uploaded on 09/14/2009 for the course ISS 731 taught by Professor A.arbogast during the Summer '09 term at Michigan State University.

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lesson 5 - Composition of the Atmosphere In this lesson, we...

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