1. Earth’s atmosphere supports life
Section 1.1
Earth’s atmosphere supports life

2. How does the atmosphere support life?
The atmosphere allows us to breathe. Many different types of organisms need oxygen to perform life processes. Plants require carbon dioxide to undergo photosynthesis. The atmosphere protects all living things from much of the Sun’s dangerous radiation. (UV radiation) The atmosphere keeps us warm! Without it, the Earth would be very cold or very hot. The atmosphere is closely related to temperature regulation and gives us weather. Organisms rely on water to survive and complex weather patterns (trade-winds and jet streams) are part of the atmospheric circulation that distributes heat around the Earth. The atmosphere protects us from objects coming toward Earth from outer space. Before meteors c become meteorites, they are burned up. The atmosphere’s air flow makes flight possible. The atmosphere carries waves that allow us to talk. The air Without the atmosphere, we wouldn’t be able to enjoy music. 

3. The Atmosphere’s characteristics
The atmosphere mostly made up of gases (approx. 78% nitrogen, 21% oxygen, and 1% argon, carbon dioxide, and other gases. The atmosphere also contains tiny particles of dust, sea salt, and water droplets. As the altitude increases (moving upward into the sky), the air’s density decreased (becomes thinner). Most of the mass of the atmosphere is close to the Earth’s surface.

4. Cycles of Nature and the Atmosphere
The carbon, nitrogen and water cycles (all necessary for life) rely on the atmosphere to “recycle” important materials. All of these cycles move from the atmosphere to Earth.

5. Sudden changes impacting our atmosphere
Sudden events, such as volcanic eruptions, forest fires, and dust storms, send gases and materials into the atmosphere. It may take a long time before the atmosphere can restore balance again. This can have a serious impact on life on Earth.

6. Think about it…
When a tiger exhales carbon dioxide, does it go directly into the plants around it? Explain. How did decaying leaves get nitrogen? If water vapor stayed in the atmosphere and did not return to Earth’s surface, how would it affect the trees in your yard?