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Plants Kick Started Oxygenation and Evolution

Plants Kick Started Oxygenation and Evolution. By Khadija Haq, Sarah Markiewicz, Rebecca Benfield, and Heather Humphrey Group A47. Introduction. The rise of oxygen is correlated with the evolution of the earth’s organisms.

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Plants Kick Started Oxygenation and Evolution

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  1. Plants Kick Started Oxygenation and Evolution By Khadija Haq, Sarah Markiewicz, Rebecca Benfield, and Heather Humphrey Group A47

  2. Introduction • The rise of oxygen is correlated with the evolution of the earth’s organisms. • Levels of Molybdenum isotopes are measured to prove two major oxidation events • Emergence of vascular plants contributed to the rise of oxygen levels http://www.sciencedaily.com/releases/2010/10/101008121348.htm

  3. Method • Molybdenum (Mo) reacts with H2S • If there is no H2S Mo will sink to the bottom of the ocean • Measured variations in isotopic compostions of Mo with mass spectrometry (Anbar) http://www.pnas.org/content/107/42/17911.full.pdf+html

  4. Data/Results • Two major ocean oxidation episodes: • Phanerozoic period-increase from 1.1 % to 1.4 % • Silurian to Devonian period-increase to 2% • Greater amount of sulfer, lower concentration of seawater Mo, lower concentration in black shale • “Therefore, observed patterns of increase in... Mo in black shales are both coincident and consistent with the Mo isotope evidence for a two-stage increase in ocean oxygenation” (Dahl).

  5. Effects • Fossils of predatory fish • Required more oxygen for energy consumption • Vascular plants • Not easily decomposable • Emerged as a result of high levels of oxygen • Photosynthesis • Abundance of oxygen • Organic carbon buried in ocean sediment

  6. Discussion • Mo in shale is linked to oxidation of the oceans and the atmosphere • After initial oxygenation, some plants and animals were able to survive in the low levels of oxygenation • After the second major oxidation event, plants and animals heavily reliant on oxygen are also able to survive http://www.pnas.org/content/107/42/17911.full.pdf+html

  7. Conclusion • Cambrian explosion first occurred with oxygen levels significantly lower than we have today • Formation of ‘black shales’ with presence of Molybdenum indicate lower level of sulfur and higher level of oxygen • Large predatory fish creatures appeared, as well as vascular plants • Co-Evolution: Environmental Change can drive Biological Evolution. Likewise Biological Evolution can drive Environmental Change (Anbar).

  8. Literature Cited • Anbar, Ariel. "Ariel Anbar's Group at Arizona State University." Ariel Anbar's Group at Arizona State University. N.p., n.d. Web. 11 Sept. 2012. <http://www.anbarlab.org/>.Arizona State University (2010, October 9). Plants kick-started evolutionary drama of Earth's oxygenation. ScienceDaily. Retrieved September 11, 2012, from http://www.sciencedaily.com­ /releases/2010/10/101008121348.htmGreen, Jenny. "ASU: School of Space." SESE. N.p., n.d. Web. 7 Sept. 2012. <sese.asu.edu/node/839 >T. W. Dahl, E. U. Hammarlund, A. D. Anbar, D. P. G. Bond, B. C. Gill, G. W. Gordon, A. H. Knoll, A. T. Nielsen, N. H. Schovsbo, D. E. Canfield. Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1011287107

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