1. The Evolution of the Atmosphere: 4.6 billion years ago - present
NOTES
The Evolution of the Atmosphere: 4.6 billion years ago - present
Mr. Chary

2. collision of smaller planets.
NOTES
4.6 billion years ago
Earth is formed by the
collision of smaller planets.

3. NOTES
4.5 billion years ago
Formation of the Moon

4. NOTES 4.2 billion years ago Early Atmosphere No Life!
Volcanoes add carbon dioxide,
ammonia, water vapor and
methane to the atmosphere.

5. NOTES
It was very HOT!

6. Earth Cools to Below 100 deg. C
NOTES
3.8 billion years ago
Earth Cools to Below 100 deg. C
Liquid Water Present
Early Oceans Form

7. NOTES
First Bacteria
(Prokaryotic)

8. Photosynthesis Produces Oxygen!
NOTES
3.5 billion years ago
Photosynthesis Produces Oxygen!

9. Stromatolites Formed by colonies cyanobacteria.
At least 3.5 billion years old.
Carbon is stored in stromatolites.
Fact:
Chloroplasts are actually cyanobacteria living in plant cells!

10. Stromatolites, colonies of cyanobacteria, are alive in Australia today.
Interesting fact to tie the past to the present
Shark Bay, Australia

11. Photosynthesis Produces Oxygen!
NOTES
2.1 billion years ago
Photosynthesis Produces Oxygen!
Oxygen + Ammonia =
Nitrogen was also produced by decaying organisms
NITROGEN!

12. 2-3 billion years ago: Little free oxygen
Commonly occur in sedimentary rocks 2-3 billion years old.
Alternating dark bands (containing FeO) and light bands of chert (silica and Fe2O3).
Occur from the deposition of alternately dissolved FeO & chert.
“Bands” occur from fluctuating densities of bacteria in an ocean. When bacteria blossoms, it creates oxygen and thus chert, which falls to the ocean floor. An oxygen depletion allows for FeO.
Banded iron formation

13. Beginning of Oxygenated Atmosphere
NOTES
2 billion years ago
Beginning of Oxygenated Atmosphere

14. Evidence of significant free oxygen
Red beds
Occur earlier than 2 billion years ago.
Form when iron is weathered out of rock in the presence of oxygen.
Evidence of significant free oxygen

15. Single-celled Eukaryotes Appear
NOTES
1.7 billion years ago
Single-celled Eukaryotes Appear
Cells get a nucleus!

16. Multi-celled Plants Appear
NOTES
1.2 billion years ago
Multi-celled Plants Appear
Photosynthesis adds more ___???___.

17. Multi-celled Plants Appear
NOTES
1.2 billion years ago
Multi-celled Plants Appear
Photosynthesis adds more OXYGEN.

18. Oxygen is at current levels.
NOTES
600 million years ago
- NOW
Oxygen is at current levels.
Still Present:

19. Compare the original composition of the atmosphere to the present day one. It is very different!

20. NOTES
Summary
Volcanoes add carbon dioxide, ammonia, methane, and water vapour to the atmosphere.
Single-celled plants begin to photosynthesize which decreases the amount of carbon dioxide and increases the amount of oxygen in the atmosphere. The oxygen reacts with ammonia from volcanoes to add nitrogen to the atmosphere.
Multi-celled plants evolved which adds even more oxygen to the atmosphere.

21. Review Questions
Millions of years ago, the atmosphere contained the following gases:
Ammonia, carbon dioxide, methane, nitrogen, oxygen and water vapor.
1. Which of these gases has increased?
2. Which of these gases has decreased?

22. Review Questions
3. Does photosynthesis increase or decrease the amount of oxygen in the atmosphere?
WHY?
4. Does photosynthesis increase or decrease the amount of carbon dioxide in the atmosphere?

23. Review Questions 5. How did volcanoes change the atmosphere?
6. How did single-celled plants change the atmosphere?
7. How do multi-celled plants change the atmosphere?

24. To think about…
How is the composition of the atmosphere changing today?

25. Picture Sources http://rainbow.ldeo.columbia.edu/courses/v1001/7.html

26. Information Sources