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Recap of Archean Proterozoic life

Recap of Archean Proterozoic life. zvf. Recap. Origin of our solar system ~ 15 Ga Origin of the Earth ~ 4.6 Ga First atmosphere: gases emitted from Earth’s liquid surface assumed to be rich in water vapour, hydrogen, hydrogen chloride, carbon monoxide, carbon dioxide and nitrogen

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Recap of Archean Proterozoic life

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  1. Recap of ArcheanProterozoic life zvf

  2. Recap • Origin of our solar system ~ 15 Ga • Origin of the Earth ~ 4.6 Ga • First atmosphere: gases emitted from Earth’s liquid surface • assumed to be rich in water vapour, hydrogen, hydrogen chloride, carbon monoxide, carbon dioxide and nitrogen • Chemical rxns resulted in abundant CH4 and NH3 • First atmosphere: gases emitted from Earth’s liquid surface • First ocean: Volcanic emissions cooled, condensed to form liquid water. Salts from circulation through mid ocean ridges and weathering. • First continents: small and thin and rapidly moving due due to hot core (sedimentary record Greenstone belts and BIFs) • Archean record: most of the rock recycled or degraded

  3. Life in the Proterozoic • Radical transition from prokaryotes to eukaryotes to metazoans!

  4. Archean Life – fossil evidence • Stromatolites • 3.5 Ga • Suggest photosynthesis • Could be non-photosynthetic bacteria

  5. Carbonate Systems • Stromatolites • Cyanobacteria mats trap sediments • The domal morphology of biological stromatolites is the result of the vertical growth necessary for infiltration of sunlight

  6. Stromatolites Stromatolites 1.8 Ga: Great Slave Lake, Canada evolution.berkeley.edu/evolibrary/images/stro..

  7. 2.2 – 2.4 Ma Stromatolite http://www.fossilmall.com/Stromatolite.htm

  8. Stromatolites • A layer of mucous often forms over mats of cyanobacterial cells. • In modern microbial mats, debris becomes trapped within the mucous, which can be cemented together by the calcium carbonate to grow thin laminations of limestone. • These laminations can accrete over time, resulting in the banded pattern common to stromatolites. Modern stromatolites – Shark Bay, Australia

  9. Modern stromatolites Stromatolites, believed to be one of the earliest forms of life on earth. remnants of them can be found in the very old geologic record, and we know what they are because they still exist today, like the ones you see here. photo courtesy of R.V. Burne http://eaps.mit.edu/geobiology/biomarkers/whatis.html

  10. Paleo- and Mesoproterozoic life • Proliferation of Stromatolites • Proliferate 2.2 Ga • Diverse shapes 1.2 Ga • Their success is attributed to the increase in size of the continents and associated increase in the breadth of continental shelves (where they live)

  11. Burial of C – further evidence for high rates of photosynthesis • Some of the oxygen building up in the atmosphere was used in decomposition of C • Some was buried • This explains the accumulation of heavy d13C in limestones that built up between 2.2 and 2 Ga • What should be the consequence of increased C burial?

  12. Prokaryotes: No membrane-bound organelles No nucleus Eukaryotes: Membrane bound organelles Nucleus Primary characteristics of prokaryotes and eukaryotes

  13. Dr. Lynn Margulis (born March 15, 1938) Department of Geosciences at the University of Massachusetts, Amherst. She is best known for her theory on the origin of eukaryotic organelles -endosymbiotic theory Endosymbiotic theory

  14. Proliferation of Eukaryotes • Union of 2 prokaryotic cells • Mitochondrian • Allow cells to derive energy from their food by respiration • Evolved from a prokaryotic cell • Chloroplast • Site of photosynthesis • Protozoan consumed, retained cyanobacterial cell

  15. Evidence for endosymbiotic origin of plastids • Mitochondria and plastids contain DNA that is similar to that of bacteria (circular). • They are surrounded by two or more membranes, and the innermost resembles in composition a prokaryotic cell membrane. • Much of the internal structure and biochemistry of plastids is very similar to that of cyanobacteria. • Phylogenetic estimates constructed with bacteria, plastids, and eukaryotic genomes also suggest that plastids are most closely related to cyanobacteria.

  16. Primary and secondary endosymbiosis • Primary endosymbiosis involves the engulfment of a bacterium by another free living organism. • Secondary endosymbiosis occurs when the product of primary endosymbiosis is engulfed and retained by another free living eukaryote. • Secondary endosymbiosis has occurred several times and has given rise to extremely diverse groups of algae and other eukaryotes.

  17. Many endosymbiotic events Many endosymbiotic events created many different types of eukaryotes There is evidence of 2 (or more) groups of phytoplankton in the Paleoproterozoic There is evidence of many of the groups by the Neoproterozoic

  18. Proliferation of eukaryotes - evidence • Biomarker evidence of precursor eukaryotes at 2.7 Ga (steranes - sterols of cell membranes of eukaryotes) • Fossil evidence of actual eukaryotes from the Proterozoic • In the Paleoproterozoic they are predominantly single cells or filaments

  19. Fossil evidence of algae in the Paleo- and Mesoproterozoic • Prokaryotic forms • outnumber the eukaryotic forms in the early Proterozoic Lake Superior Gunflint Chert ~2 Ga Prokaryotes – small and simple Eukaryotes - Bigger and more complex

  20. Algae • More complex forms follow • Algal ribbons wound into loose coils • 2.1 Ga

  21. Acritarchs – key eukaryote in the Proterozoic • Interpreted as eukaryotic cells and become dominant part of the plankton • Many are spherical some may pointed, surface can be covered with processes • Likely polyphyletic • Diversify through the Proterozoic • Many look like cysts of dinoflagellates

  22. Polyphyletic group Covered with organic armour Characterisitic flagella Unicellular and chain formers Many auto- mixo- and heterotrophs Coastal bloom formers Form toxins: PSP, etc. Many form resistant cysts that fossilize Dinoflagellates

  23. Extant dinoflagellate cysts Fabienne Marret and Karin A. F. Zonneveld (2003) Atlas of modern organic-walled dinoflagellate cyst distribution. Review of Palaeobotany and Palynology, Volume 125, Issues 1-2, Pages 1-200 Ataxodinium choane Bitectadinium tepikiense Bitectadinium spongium Cyst of Alexandium tamarense Impagidinium aculeatum Spiniferites mirabilis

  24. Dinoflagellates • Potential ecological consequences of the radiation of the acritarchs if • Some photosynthetic • Some mixotrophic • Some heterotrophic • Emergence of a complex ecosystem with more than one trophic level develops in the Proterozoic

  25. Consequences of the Eukaryote proliferation • This may have triggered an arms race between predators and prey • This may have stimulated diversification of lineages

  26. Predator-prey diversity relationship (Rosenweig, 1995)

  27. The importance of predation • Predators may prevent competitive exclusion of species with similar requirements • This may increase biodiversity • Biodiversity may alter function • May increase rate or magnitude of recycling and may increase primary production • May have had consequences for C burial

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