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EVOLUTION OF PHOTOSYNTHESIS & AEROBIC RESPIRATION

EVOLUTION OF PHOTOSYNTHESIS & AEROBIC RESPIRATION. by C. Grier Sellers Doctoral Candidate in Biology NSF GK12 Fellow Temple University. History of the Earth: Four Eons:. Hadean Eon: 4500 - 3800 millions of years ago (mya) Archean Eon: 3800 - 2500 mya Proterozoic Eon: 2500 - 542 mya

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EVOLUTION OF PHOTOSYNTHESIS & AEROBIC RESPIRATION

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  1. EVOLUTION OF PHOTOSYNTHESIS & AEROBIC RESPIRATION by C. Grier Sellers Doctoral Candidate in Biology NSF GK12 Fellow Temple University

  2. History of the Earth: Four Eons: • Hadean Eon: 4500 - 3800 millions of years ago (mya) • Archean Eon: 3800 - 2500 mya • Proterozoic Eon: 2500 - 542 mya • Phanerozoic Eon: 542 mya - Present

  3. http://en.wikipedia.org/wiki/Geologic_time_scale

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

  5. Archean Eon:(Image: American Museum of Natural History) • 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)

  6. Photosynthetic Bacteria: • Some photosynthetic bacteria (such as green sulfur bacteria) use Hydrogen sulfide (H2S) & do not produce oxygen: H2S + CO2 + Light --> Sugars + Sulfur • Cyanobacteria (& in eukaryotes, chloroplasts) use water instead, & produce oxygen: H2O + CO2 + Light --> Sugars + O2

  7. Cyanobacteria: http://universe-review.ca/F11-monocell.htm

  8. Key Dates in the Early Evolution of Life: • 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

  9. 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. Oxygen Terminology:

  10. The Oxygen Revolution: • The first O2 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.

  11. Gradual Increase in Atmospheric O2: http://www3.ncc.edu/faculty/bio/fanellis/biosci119/marineorg.html

  12. Banded Iron Formation:(c. 2400 mya)formed by the oxidation of iron, forming rust http://rst.gsfc.nasa.gov/Sect19/Sect19_2a.html

  13. Consequences of Oxygen in the Environment: • 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

  14. Acknowledgements: Temple University “Scientists as Teachers / Teachers as Scientists Program” National Science Foundation GK12 Grant

  15. References: Falkowski, P.G.& Raven, J.A. (2007) Aquatic Photosynthesis, Princeton, NJ: Princeton University Press. Knoll, A.H. (2003) Life on a Young Planet: The First Three Billion Years of Evolution on Earth, Princeton, NJ: Princeton University Press. Margulis, L. (1993) Symbiosis in Cell Evolution: Microbial Communities in the Archean & Proterozoic Eons, New York, NY: W.H. Freeman & Co. Margulis, L. & Dolan, M.F. (2002) Early Life: Evolution on the Precambrian Earth, Sudbury, MA: Jones & Bartlett Publishers.

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