1. Unit 3: Gases and the Atmosphere Atmosphere: the mass of air surrounding the earth.

2. Today’s Composition of the Atmosphere

3. Has the composition of the atmosphere of the earth changed over time? Yes. The atmosphere has evolved over time, just like everything else. 1.Origin 2.Chemical Era 3.Microbial Era 4.Biological Era

4. The Biological Era The atmosphere has not always been as it is today - and it will change again in the future. It is closely controlled by life and, in turn, controls life processes. Oxygen was built up slowly over time, first oxidizing materials in the oceans and then on land Sometime just before the Cambrian, atmospheric oxygen reached levels close enough to today's to allow for the rapid evolution of the higher life forms.

6. Sources of Oxygen Oxygen is liberated as a by-product of photosynthetic chemical reactions. Oxygen occurs in the atmosphere when water molecules are split apart after being struck with UV radiation. This process is called photolysis. – H 2 O  H 2 + O – The hydrogen molecule is light, and has a quick thermal velocity,so it can escape Earth's atmosphere leaving behind the free oxygen to form O 2 and O 3. The main source of this atmospheric water was volcanic eruptions and outgassing. Basically before photosynthesis began on large scales, free oxygen molecules in the atmosphere were drawn down in oxidation reactions with free metal ions on the Earth's surface, mainly iron. Even when photosynthetic organisms were taking control of the atmosphere, the free oxygen molecules were being placed into the rock record in oxidation reactions. This forms red colored rocks, like you find in the southwestern United States. Because of this, early Earth had a reducing atmosphere, composed mainly of methane,carbon dioxide, water, carbon monoxide, and nitrogen. This would be a very hostile place to most modern forms of life.

7. Ozone Proved to be important in filtering out the high damaging levels of radiation from the sun. This led to the development of more complex species.

8. CO 2 Levels over Time YearCO 2 Concentration (ppmv)T Anomaly (°C off normal) 1840280-0.40 1955310-0.05 19603120.00 1965316-0.10 1970320-0.08 1975327-0.08 1980335-0.08 1985345+0.10 1990352+0.15 1995355+0.25 2000360+0.28

9. Based on this information: What conclusions can you draw from ONLY studying this data?

10. Autism and Vaccines

11. The real cause of autism?

13. CO 2 Assignment Research average temperatures in Manitoba and CO 2 levels. Graph the results. 1. Describe what information you can interpret from the graph. 2. Why are levels of CO 2 increasing? 3. How is this increase leading to climate change? 4. Do you think CO 2 levels will stop increasing?