Paleoproterozoic

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Paleoproterozoic Era
2500 - 1600 million years ago
Key events in the Paleoproterozoic
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An approximate timescale of key Paleoproterozoic events.
Axis scale: millions of years ago.

Paleoproterozoic Era ( /pæliˌprtərəˈzɪk-/;[1][2]), spanning the time period from 2,500 to 1,600 million years ago (2.5–1.6 Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's geological history. It was during this era that the continents first stabilized.

Paleontological evidence suggests that the Earth's rotational rate during this era resulted in 20-hour days ~1.8 billion years ago, implying a total of ~450 days per year.[3]

Paleoatmosphere

Before the enormous increase in atmospheric oxygen, almost all existing lifeforms were anaerobic, i.e., their metabolism was based upon a form of cellular respiration that did not require oxygen. Indeed, free oxygen in large amounts is toxic to most anaerobic organisms. Consequently, the majority of the anaerobic lifeforms on Earth died when the atmospheric free-oxygen levels soared. The only lifeforms that survived were either those resistant to the oxidizing and poisonous effects of oxygen, or those sequestered in oxygen-free environments. The sudden increase of atmospheric free oxygen and the ensuing extinction of the vulnerable lifeforms (an event called, among numerous other similarly suggestive titles, the Oxygen Holocaust or Oxygen Catastrophe) is widely considered to be the first of the most significant mass extinctions in the history of the Earth.[4]

Emergence of Eukarya

Many crown node eukaryotes (from which the modern-day eukaryotic lineages would have arisen)—or the divergences that imply them between various groups of eukaryotes—have been ostensibly dated to around the time of the Paleoproterozoic era.[5][6][7] However, these conclusions (as is the case in virtually any contemporaneously "hot" areas of biological study and research) are likely to be readjusted—if not outright abandoned—as more data become available, and should not be considered conclusive proof by any means. Nevertheless, given the number of and the peer respect assigned to many of the authors of these studies (and related analyses corroborating the validity of the methodologies used by those studies[8][9][10][11][12] ...even though those very analyses are themselves also sometimes called into question[13][14]), the final revisions will likely place the emergence of the oldest eukaryotic divergences around this period of time.[15][16][17][18][5][6][7]

Geological events

During this era, the earliest global-scale continent-continent collision belts developed.

These continent and mountain building events are represented by the 2.1–2.0 Ga Trans-Amazonian and Eburnean orogens in South America and West Africa; the ~2.0 Ga Limpopo Belt in southern Africa; the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava and Torngat orogens in North America, the 1.9–1.8 Ga Nagssugtoqidain Orogen in Greenland; the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volhyn-Central Russian, and Pachelma orogens in Baltica (Eastern Europe); the 1.9–1.8 Ga Akitkan Orogen in Siberia; the ~1.95 Ga Khondalite Belt and ~1.85 Ga Trans-North China Orogen in North China.

These continental collision belts are interpreted as having resulted from one or more 2.0–1.8 Ga global-scale collision events that then led to the assembly of a Proterozoic supercontinent named Columbia or Nuna.[19][20]

The lithospheric mantle of Patagonia's oldest blocks formed.[21]

See also

(Impact events)

References

  1. ^ "palaeo-". Oxford Dictionaries. Oxford University Press. Retrieved 2016-01-20.  "Proterozoic". Oxford Dictionaries. Oxford University Press. Retrieved 2016-01-20. 
  2. ^ "Proterozoic". Merriam-Webster Dictionary. 
  3. ^ Pannella, Giorgio (1972). "Paleontological evidence on the Earth's rotational history since early precambrian". Astrophysics and Space Science. 16 (2): 212. Bibcode:1972Ap&SS..16..212P. doi:10.1007/BF00642735. 
  4. ^ Margulis, Lynn; Sagan, Dorion (1997-05-29). Microcosmos: Four Billion Years of Microbial Evolution. University of California Press. ISBN 9780520210646. 
  5. ^ a b Hedges, S Blair; Chen, Hsiong; Kumar, Sudhir; Wang, Daniel YC; Thompson, Amanda S; Watanabe, Hidemi (2001-09-12). "A genomic timescale for the origin of eukaryotes". BMC Evolutionary Biology. 1: 4. doi:10.1186/1471-2148-1-4. ISSN 1471-2148. PMC 56995Freely accessible. PMID 11580860. 
  6. ^ a b Knoll, A.H; Javaux, E.J; Hewitt, D; Cohen, P (2006-06-29). "Eukaryotic organisms in Proterozoic oceans". Philosophical Transactions of the Royal Society B: Biological Sciences. 361 (1470): 1023–1038. doi:10.1098/rstb.2006.1843. PMC 1578724Freely accessible. PMID 16754612. 
  7. ^ a b Hedges, S Blair; Blair, Jaime E; Venturi, Maria L; Shoe, Jason L (2004-01-28). "A molecular timescale of eukaryote evolution and the rise of complex multicellular life". BMC Evolutionary Biology. 4: 2. doi:10.1186/1471-2148-4-2. ISSN 1471-2148. PMC 341452Freely accessible. PMID 15005799. 
  8. ^ Webster, AJ; Purvis, A (2002). "Testing the accuracy of methods for reconstructing ancestral states of continuous characters" (PDF). Proc Biol Sci. 269: 143–9. doi:10.1098/rspb.2001.1873. PMC 1690869Freely accessible. PMID 11798429. 
  9. ^ Wray, Gregory A (2002). "Dating branches on the Tree of Life using DNA". Genome Biology. 3 (1): reviews0001.1–reviews0001.7. doi:10.1186/gb-2001-3-1-reviews0001. ISSN 1465-6906. PMC 150454Freely accessible. PMID 11806830. 
  10. ^ Kishino, H.; Thorne, J. L.; Bruno, W. J. (March 2001). "Performance of a divergence time estimation method under a probabilistic model of rate evolution". Molecular Biology and Evolution. 18 (3): 352–361. doi:10.1093/oxfordjournals.molbev.a003811. ISSN 0737-4038. PMID 11230536. 
  11. ^ Ayala, Francisco José; Rzhetsky, Andrey; Ayala, Francisco J. (1998-01-20). "Origin of the metazoan phyla: Molecular clocks confirm paleontological estimates". Proceedings of the National Academy of Sciences of the United States of America. 95 (2): 606–611. doi:10.1073/pnas.95.2.606. ISSN 0027-8424. PMC 18467Freely accessible. PMID 9435239. 
  12. ^ Sanderson, Michael J. (January 2002). "Estimating absolute rates of molecular evolution and divergence times: a penalized likelihood approach". Molecular Biology and Evolution. 19 (1): 101–109. doi:10.1093/oxfordjournals.molbev.a003974. ISSN 0737-4038. PMID 11752195. 
  13. ^ Rodríguez-Trelles, Francisco; Tarrío, Rosa; Ayala, Francisco J. (2002-06-11). "A methodological bias toward overestimation of molecular evolutionary time scales". Proceedings of the National Academy of Sciences of the United States of America. 99 (12): 8112–8115. Bibcode:2002PNAS...99.8112R. doi:10.1073/pnas.122231299. ISSN 0027-8424. PMC 123029Freely accessible. PMID 12060757. 
  14. ^ Shaul, Shaul; Graur, Dan (2002-10-30). "Playing chicken (Gallus gallus): methodological inconsistencies of molecular divergence date estimates due to secondary calibration points". Gene. 300 (1–2): 59–61. doi:10.1016/s0378-1119(02)00851-x. ISSN 0378-1119. PMID 12468086. 
  15. ^ Stechmann, Alexandra; Cavalier-Smith, Thomas (2002-07-05). "Rooting the eukaryote tree by using a derived gene fusion". Science. 297 (5578): 89–91. Bibcode:2002Sci...297...89S. doi:10.1126/science.1071196. ISSN 1095-9203. PMID 12098695. 
  16. ^ Wang, D Y; Kumar, S; Hedges, S B (1999-01-22). "Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi". Proceedings of the Royal Society B: Biological Sciences. 266 (1415): 163–171. doi:10.1098/rspb.1999.0617. PMC 1689654Freely accessible. PMID 10097391. 
  17. ^ Baldauf, S. L. (2003-06-13). "The deep roots of eukaryotes". Science. 300 (5626): 1703–1706. Bibcode:2003Sci...300.1703B. doi:10.1126/science.1085544. ISSN 1095-9203. PMID 12805537. 
  18. ^ Knoll, A. H. (1992-05-01). "The early evolution of eukaryotes: a geological perspective". Science. 256 (5057): 622–627. Bibcode:1992Sci...256..622K. doi:10.1126/science.1585174. ISSN 0036-8075. PMID 1585174. 
  19. ^ Zhao, Guochun; Cawood, Peter A; Wilde, Simon A; Sun, Min (2002). "Review of global 2.1–1.8 Ga orogens: implications for a pre-Rodinia supercontinent". Earth-Science Reviews. 59: 125–162. Bibcode:2002ESRv...59..125Z. doi:10.1016/S0012-8252(02)00073-9. 
  20. ^ Zhao, Guochun; Sun, M.; Wilde, Simon A.; Li, S.Z. (2004). "A Paleo-Mesoproterozoic supercontinent: assembly, growth and breakup". Earth-Science Reviews. 67: 91–123. Bibcode:2004ESRv...67...91Z. doi:10.1016/j.earscirev.2004.02.003. 
  21. ^ Schilling, Manuel Enrique; Carlson, Richard Walter; Tassara, Andrés; Conceição, Rommulo Viveira; Berotto, Gustavo Walter; Vásquez, Manuel; Muñoz, Daniel; Jalowitzki, Tiago; Gervasoni, Fernanda; Morata, Diego (2017). "The origin of Patagonia revealed by Re-Os systematics of mantle xenoliths". Precambrian Research. 294: 15–32. Bibcode:2017PreR..294...15S. doi:10.1016/j.precamres.2017.03.008. 

External links

  • EssayWeb Paleoproterozoic Era
  • First breath: Earth's billion-year struggle for oxygen New Scientist, #2746, 5 February 2010 by Nick Lane. Posits an earlier much longer snowball period, c2.4 - c2.0 Gya, triggered by the Great Oxygenation Event.
  • The information on eukaryotic lineage diversification was gathered from a New York Times opinion blog by Olivia Judson. See the text here: [1].
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