1. 1 Photosynthesis (Process that changed history) Light energy + CO 2 + H 2 O  glucose + O 2 IMPORTANT POINTS:  Example of 1 st Law of Thermodynamics: (E conservation) Radiant energy (light)  chemical energy (glucose)  Carbon from atmosphere locked into an organic molecule (glucose) Carbon – fixation! (This point covered for Test IV)  Water molecules split  O 2 gas is released!

2. Evolution of the Earth’s Atmosphere The Continuing Story

3. 3 Major Episodes in the History of Life Visual Summary 15.1 Millions of years ago 475 570 1,000 1,700 2,500 3,500 4,500 Major Episode Plants and fungi colonize land All major animal phyla established First multicellular organisms Oldest eukaryotic fossils Accumulation of atmospheric 0 2 Oldest prokaryotic fossils Origin of Earth

4. 4 4.5 BYA Earth Formed What was original atmosphere like?

5. 5 3.5 BYA Life appeared! (Prokaryotic) Q: Did these organisms need oxygen to live? Then some “New guys” appeared……

6. 6 Cyanobacteria or “blue-green algae”

7. 7 2.5 BYA Significant build up of oxygen gas in Earth’s atmosphere (Due to photosynthesis!) Many original inhabitants die due to this “Pollution Crises!” Some organisms adapt & use O 2 to release stored energy of food.

8. 8 1.7 – 1.5 BYA The Rise of Eukaryotes! First: Protists  plants, animals, & fungi 1.0 BYA Life experiments with multi-cellularity!

9. 9 ~ ½ BYA (570mya) CAMBRIAN EXPLOSION! All major animal phyla established! ( 470 mya)  Terrestrial life appears (First Fungi & plants, then animals)  What was necessary for terrestrial life?

10. 10 OZONE! O 2 + O 2 + O 2 = 2 O 3 Why is Ozone so important? *