1. Composition of the Atmosphere Through Time and the Impact on Living Things

2. Earth’s Atmosphere The gases that surround Earth (and other planets) make up the atmosphere – These gases are like an envelope that protects us from the radiation that is caused by the sun’s rays – The functions of the atmosphere include protection from the sun, maintaining temperature, and supplying gases necessary for breathing.

3. Layers of the Atmosphere The atmosphere is divided into four layers based on temperature, air pressure, and other properties. Troposphere (closest to Earth) Stratosphere Mesosphere Thermosphere (ionosphere and exosphere)

4. Layers of the Atmosphere

5. The Thermosphere The thermosphere is the uppermost layer with temperatures that increase as altitude increases. Made up of the ionosphere and exosphere auroras happen in the ionosphere sattelites orbit in the exosphere Hottest of the layers Air is very thin (the air is only about 0.001 percent as dense as the air at sea level)

6. The Mesosphere The mesosphere is between the thermosphere and stratosphere. Temperatures decrease as altitude increases. Coldest layer Meteoroids begin to burn up in the mesosphere. Radio waves deflected back to Earth in this layer

7. The Stratosphere The stratosphere is between the mesosphere and troposphere. Temperatures generally increase as altitude increases. Ozone (O 3 ) in the stratosphere absorbs ultraviolet radiation from the sun, which warms the air. Jets fly in this layer Jet streams (“rivers of air”) are found in this layer

8. The Troposphere The troposphere is the lowest layer of the atmosphere. Temperature generally decreases as altitude increases. Temperatures near the surface vary greatly. The troposphere contains 80 percent of the atmosphere’s total mass. All weather happens in the troposphere.

9. QUIZ TIME

10. What are the layers of the atmosphere? How do temperatures differ with altitude in the atmosphere?

11. EXOSPHERE

12. MESOSPHERE

13. THERMOSPHERE

14. TROPOSPHERE

15. STRATOSPHERE

16. THERMOSPHERE OR THE IONOSPHERE

17. MESOSPHERE

18. Atmosphere Over Time The composition of the atmosphere has changed

19. Earliest/First Atmosphere It is hypothesized that the earliest atmosphere was composed of mainly H 2 and He Most likely these gases were lost to space As this is a hypothesis, percentages are unknown Based on this hypothesis, living things did not exist

20. Represent with a Graph Scatter two different colored M&Ms on your pie chart

21. Second Atmosphere There is evidence to suggest that the gases that made up the second atmosphere were H 2 O, CO 2, SO 2, CO, S 2, Cl 2, N 2, H 2, NH 3 (ammonia), and CH 4 (methane) These gases were caused by early volcanoes This atmosphere contained approximately 90% CO 2, 5% N 2, and 2% - 5% trace gases

22. Second Atmosphere’s Impact on Living Things As Earth cooled over time, oceans formed – Oceans are made of H 2 O (water) This allowed for the first life forms -- bacteria These ancient bacteria survived because they used CO 2 (carbon dioxide) to photosynthesize One of the products of photosynthesis is O 2 (oxygen gas)

23. Represent with a Graph 90% (carbon dioxide) 5% (nitrogen gas) 2-5% (trace gases)

24. Today’s Atmosphere Our atmosphere contains approximately 78% N 2, 21% O 2, and 1% trace gases N 2 remains from the second ancient atmosphere CO 2 levels decreased to approximately 0.03%. – CO 2 (along with other gases) levels have a large impact on our climate because of its ability to trap heat Without CO 2, the Earth would be approximately 0 o F

25. Impact on Living Things Plants and animals maintain the balance of CO 2 and O 2 through the processes of photosynthesis and cellular respiration This allows for the production of oxygen and the consumption of carbon dioxide

26. Represent with a Graph 78% (nitrogen gas) 21% (oxygen gas) 1% (trace gases)

27. What Happens Next? We will be looking at how human’s have impacted our atmosphere and therefore Earth. – Topics: Global Warming Greenhouse Effect