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7.1: Importance of the Atmosphere

Difficulty Level: Basic Created by: CK-12
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Why is the Atmosphere Important?

Why is Earth the only planet in the solar system known to have life? The main reason is Earth’s atmosphere. Organisms need the gases in the atmosphere to live. Water is also essential for life. Water vapor is one of the gases in the atmosphere. Green algae, like in this photo, are primitive life.

The Atmosphere

The atmosphere is a mixture of gases that surrounds the planet. We also call it air. The gases in the atmosphere include nitrogen, oxygen, and carbon dioxide. Along with water vapor, the atmosphere allows life to survive. Without it, Earth would be a harsh, barren world.

Why the Atmosphere Is Important

We are lucky to have an atmosphere on Earth. The atmosphere supports life, and is also needed for the water cycle and weather. The gases of the atmosphere even allow us to hear.

The Atmosphere and Living Things

Most of the atmosphere is nitrogen, but it doesn't do much. Carbon dioxide and oxygen are the gases in the atmosphere that are needed for life.

  • Plants need carbon dioxide for photosynthesis. They use sunlight to change carbon dioxide and water into food. The process releases oxygen. Without photosynthesis, there would be very little oxygen in the air.
  • Other living things depend on plants for food. These organisms need the oxygen plants release to get energy out of the food. Even plants need oxygen for this purpose.
The Atmosphere and the Sun’s Rays

The atmosphere protects living things from the sun’s most harmful rays. Gases reflect or absorb the strongest rays of sunlight. Figure below models this role of the atmosphere.

The atmosphere shields Earth from the most harmful solar rays.

The Atmosphere and Earth’s Temperature

Gases in the atmosphere surround Earth like a blanket. They keep the temperature in a range that can support life. The gases keep out some of the sun’s scorching heat during the day. At night, they hold the heat close to the surface, so it doesn’t radiate out into space.

The Atmosphere and Earth’s Water

Figure below shows the role of the atmosphere in the water cycle. Water vapor rises from Earth’s surface into the atmosphere. As it rises, it cools. The water vapor may then condense into water droplets and form clouds. If enough water droplets collect in clouds they may come together to form droplets. The droplets will fall as rain. This how freshwater gets from the atmosphere back to Earth's surface.

The atmosphere is a big part of the water cycle. What do you think would happen to Earth’s water without it?

The Atmosphere and Weather

Without the atmosphere, there would be no clouds or rain. In fact, there would be no weather at all. Most weather occurs because the atmosphere heats up more in some places than others.

The Atmosphere and Weathering

Weather makes life interesting. Weather also causes weathering. Weathering is the slow wearing down of rocks on Earth’s surface. Wind-blown sand scours rocks like sandpaper. Glaciers of ice scrape across rock surfaces like a file. Even gentle rain may seep into rocks and slowly dissolve them. If the water freezes, it expands. This eventually causes the rocks to crack. Without the atmosphere, none of this weathering would happen. Rocks at the surface would be pristine and unaltered.

The Atmosphere and Sound

Sound is a form of energy that travels in waves. Sound waves can’t travel through empty space, but they can travel through gases. Gases in the air allow us to hear most of the sounds in our world. Because of air, you can hear birds singing, horns tooting, and friends laughing. Without the atmosphere, the world would be a silent, eerie place.


  • atmosphere: The layer of gases that surrounds a planet.
  • photosynthesis: The process in which plants produce simple sugars (food energy) from carbon dioxide, water, and energy from sunlight. Photosynthesis uses carbon dioxide and releases oxygen.
  • sound: Energy that travels through a medium that we can hear.


  • The atmosphere is made of gases that are essential for photosynthesis and other life activities.
  • The atmosphere is a crucial part of the water cycle. It is an important reservoir for water and the source of precipitation.
  • The atmosphere moderates Earth's temperature. Weather takes place in the atmosphere.
  • Without air, Earth would be silent.


Use these resources to answer the questions that follow.

Earth's Atmosphere: Earth Science Week at http://www.youtube.com/watch?v=CsWp25SAPq4 (1:19)

  1. What is the atmosphere?
  2. Where does weather occur?
  3. What does the atmosphere protect us from? Which layer?
  4. What happens in the mesosphere?
  5. What is made in the thermosphere?


  1. What gases are used and expelled by photosynthesis and respiration?
  2. What gases are used and what gases are produced by photosynthesis?
  3. How does the atmosphere keep Earth's temperature moderate?

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atmosphere Layer of gases that surrounds a planet.
photosynthesis Process in which plants produce simple sugars (food energy) from carbon dioxide, water, and energy from sunlight; photosynthesis uses carbon dioxide and releases oxygen.
sound Energy that travels through a medium that we can hear.

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Difficulty Level:
6 , 7
Date Created:
Jan 04, 2013
Last Modified:
Aug 29, 2016
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