Environmental Science Name: ______________________________
Chapter 7: The Atmosphere
Goal:
The student will describe the composition of the Earth’s atmosphere and describe the layers of the
Earth’s atmosphere.
Vocabulary:
1.
Atmosphere –
2.
Troposphere –
3.
Stratosphere –
4.
Ozone –
Notes: Chapter 7.1: The Atmosphere
•
Earth is surrounded by a mixture of gases known as the atmosphere
• Nitrogen, oxygen, carbon dioxide and other gases are all parts of this mixture
•
The atmosphere changes constantly as these gases are added and removed (ex: animals take in O
2
, give off CO
2
; plants take in CO
2 and give off O
2
; volcanic eruptions add gases; cars add and remove gases)
• Our atmosphere (this layer of gases) is what makes life possible on the Earth by insulating Earth’s surface, slowing the rate at which heat from the sun is lost, thus allowing us to survive
•
Extends from the surface of Earth to hundreds of kilometers above the surface
How Photosynthesis Changed the Atmosphere
• Earth’s early atmosphere probably contained very little oxygen; early organisms (bacteria) evolved the ability to perform photosynthesis
• During photosynthesis, some oxygen from water and carbon dioxide formed oxygen gas, which entered the air
•
As plants multiplied, oxygen in the air increased
• Organisms, during cellular respiration, release carbon dioxide into the atmosphere, creating the balance between the two; thus, sustaining the balance for life on Earth and keeping the planet within a temperature range for life to exist
Composition of the Atmosphere
•
AIR = 78% nitrogen (entering when volcanoes erupt, dead plants and animals decay) and 21% oxygen
(primarily produced by plants); remaining 1% is made up of water vapor, argon, carbon dioxide, methane and other gases
•
Most important gases for organisms is oxygen (cellular respiration) and carbon dioxide (photosynthesis)
• Atmosphere protects Earth’s organisms by: protecting from sun’s ultraviolet radiation, allows light to reach the surface and keeps the Earth’s temperatures stable
Air Pressure
 Earth’s atmosphere is pulled toward Earth’s surface by gravity making the atmosphere denser near the surface
 Almost the entire mass of Earth’s atmospheric gases are located with 30 km of the surface; fewer gas molecules are found at altitudes above 30 km (less pressure to push downward)

Air becomes less dense as elevation increases; breathing becomes more difficult the higher you go

The Layers of the Atmosphere
•
Atmosphere is divided into 4 individual layers (less dense the farther away from Earth) based on temperature changes that occur at different distances above the Earth’s surface
•
Troposphere – closest to the earth; extends from surface outward about 18 km; contains 90% of atmosphere’s gases; layer where weather occurs; most dense atmospheric layer; temperature decreases as altitude increases
•
Stratosphere – extends from 18 km to about 50 km (about 30 miles); temperature rise as altitude increases as a result of ozone in the stratosphere absorbing the sun’s ultraviolet energy and warming the air
•
Ozone (O
3
) is a molecule made up of three oxygen; almost all O
3
is concentrated in ozone layer in the stratosphere; Because ozone absorbs UV radiation, it reduces the amount of UV radiation that reaches the Earth. UV rays cause damage to living cells
• Mesosphere – extends from 50 to 80 km; coldest layer of the atmosphere, measured as low as -93 degrees C.
•
Thermosphere – extends from 80 to 550 km; located farthest from Earth’s surface; nitrogen and oxygen absorb solar radiation which results in temperatures above 2000 degrees C. (wouldn’t feel hot because air particles are so far apart they never collide, so little heat is transferred)
•
Nitrogen and oxygen (lower region of thermosphere) absorb harmful radiation (x-rays, gamma rays) causing them to become electrically charged (called ions). The lower region of the atmosphere is sometimes called the ionosphere. These ions radiate energy as light and oftentimes glow in spectacular colors in the night sky (North and South poles)
Lesson Reflection:
Draw the layers of the atmosphere. Color and label the diagram.
Assessment:
1.
Describe the composition of Earth’s atmosphere
2.
Describe a characteristic of each layer of the atmosphere.
Lesson Extension (Technology/Application/Connection to Real World):
Watch YouTube Video on Felix Baumgartner’s free fall from space!