2. “Photosynthesis is an ancient process that originated not long after the origin of life and has evolved via a complex path to produce the distribution of types of photosynthetic organisms and metabolisms that are found today.” http://www.plantphysiol.org/content/154/2/434.full

6. Are the most numerous on the planet Thrive during conditions that are cool and moist with normal light Get its name because the carbon dioxide is incorporated into a 3-carbon compound. RUBISCO, the enzyme involved in photosynthesis, is also the enzyme involved in the uptake of CO 2. It takes place throughout the leaf.

7. CO 2 is first incorporated into a 4-carbon compound. Stomata are open during the day. Uses PEP Carboxylase for the enzyme involved in the uptake of CO 2. This enzyme allows CO 2 to be taken into the plant very quickly, and then it "delivers" the CO 2 directly to RUBISCO for photsynthesis. Photosynthesis takes place in inner cells

8. Adaptive Value: Photosynthesizes faster than C3 plants under high light intensity and high temperatures because the CO 2 is delivered directly to RUBISCO, not allowing it to grab oxygen and undergo photorespiration. Has better water-use-efficiency because PEP Carboxylase brings in CO 2 faster, and the stomata does not need to be open as much (less water lost by transpiration) for the same amount of CO 2.

9. Named after the plant family in which it was first found (Crassulaceae) and because the CO 2 is stored in the form of an acid before use in photosynthesis. Stomata open at night (when evaporation rates are usually lower) and are usually closed during the day. The CO 2 is converted to an acid and stored during the night. During the day, the acid is broken down and the CO 2 is released to RUBISCO for photosynthesis

10. Adaptive Value: Better water-use-efficiency than C3 plants under arid conditions due to opening stomata at night when transpiration rates are lower (no sunlight, lower temperatures, lower wind speeds, etc.). When conditions are extremely arid, CAM plants can just leave their stomata closed night and day. Oxygen given off in photosynthesis is used for respiration and CO 2 given off in respiration is used for photosynthesis. This allows the plant to survive dry spells, and for the plant to recover very quickly when water is available again (unlike plants that drop their leaves and twigs and go dormant during dry spells).

11. by C. Grier Sellers Doctoral Candidate in Biology NSF GK12 Fellow Temple University

12. Hadean Eon: 4500 - 3800 millions of years ago (mya) Archean Eon: 3800 - 2500 mya Proterozoic Eon: 2500 - 542 mya Phanerozoic Eon: 542 mya - Present

14. For its first billion years, the Earth’s surface was molten rock It was too hot for life to exist or to originate

15. Prokaryotic life originated soon after Earth cooled and oceans were formed Earth was anoxic Photosynthetic bacteria, including cyanobacteria evolved (bumps are “stromatolites”, made by them)

16. Some photosynthetic bacteria (such as green sulfur bacteria) use Hydrogen sulfide (H 2 S) & do not produce oxygen: H 2 S + CO 2 + Light --> Sugars + Sulfur Cyanobacteria (& in eukaryotes, chloroplasts) use water instead, & produce oxygen: H 2 O + CO 2 + Light --> Sugars + O 2

18. Origin of Life: (the first prokaryotes) c. 3800 mya Origin of Photosynthesis: c. 3500 mya ?? Origin of Oxygenic Photosynthesis: (oldest cyanobacterial fossils) c. 2900 mya Origin of Aerobic Respiration: c. 2400 mya?? Origin of Eukaryotes: (the first protists) c. 2000 mya

19. An environment lacking oxygen is: Anoxic. Anaerobe: an organism that lives without oxygen (many are killed by oxygen). An environment containing oxygen is: Oxic. Aerobe: an organism that requires oxygen to live.

20. The first O 2 on Earth was a waste product of a new type of photosynthesis invented by cyanobacteria (oxygenic photosynthesis) This caused formation of oxidized compounds (banded iron formations - or “rusty rocks”) Oxygen first dissolved in the oceans, then accumulated in the atmosphere - it currently makes up 21% of the air.

23. Caused a mass extinction of anaerobic prokaryotes, for whom it is toxic Made evolution of aerobic respiration in bacteria possible (later, some of these oxygen-respiring bacteria were eaten by eukaryotes, and became mitochondria) These aerobic bacteria were very successful, since aerobic respiration produces much more ATP than anaerobic bacteria can produce