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Lecture_26b_DulaiS09_Endosymbiosis - The The Origin and...

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Unformatted text preview: The The Origin and Early Evolution of Life The The Big Bang 12-15 (13.8) billion years ago all matter was compressed into a space the size of? Our Galaxy Our Solar System Our Plant Our Atom Sudden instantaneous distribution of matter and energy throughout the known universe Timeline Timeline 4.6 to 3.8 billion years ago - Leads to solid crust 3.8 Water forms 2.8 to 3.2 - Life starts as prokaryotic cells 1.5 Eukaryotic cells develop 545 Cambrian explosion 500 Fish 350 Amphibians 300 Reptiles 1.6 humans Timeline: Timeline: Archaean Eon and Earlier 4,600 mya: Origin of Earth 4,600 - 3,800 mya (about 800 million years) Formation of Earth’s crust, atmosphere… Formation of the Moon Chemical and molecular evolution only Then came the First cells (anaerobic bacteria) Earth Earth Forms About 4.6 billion years ago Gas, Minerals and ice orbiting the sun started clumping together Heavy metals moved to Earth’s interior, lighter ones floated to surface Iron core Produced outer crust and inner mantle First First Atmosphere Hydrogen gas Nitrogen Carbon monoxide Carbon dioxide No gaseous oxygen Earth Earth Is “Just Right” for Life was; IF…Earth was; Smaller in diameter, gravity would not be great enough to hold onto atmosphere Closer to sun, water would have evaporated Farther from sun, water would have been locked up as ice Stanley Stanley Miller’s Experiment Mixed methane, hydrogen, ammonia, and water Simulated lightning Amino acids and other small molecules formed Animation electrodes to vacuum pump CH4 NH3 H2O H2 spark discharge gases water out condenser water in water droplets water containing organic compounds liquid water in trap boiling water How How Did Cells Originate? In the first 600 million years or so of Earth history, enzymes, ATP, and other crucial organic compounds probably assembled spontaneously - nothing came of it! Then, by a still disputed mechanism, the concoction came together randomly to make some primitive organic molecule… Possible Possible Sequence… membrane-bound proto-cells living cells self-replicating system enclosed in a selectively permeable, protective lipid sphere DNA RNA enzymes and other proteins formation of protein-RNA systems, evolution of DNA formation of lipid spheres spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions RNA RNA World now DNA is genetic material now DNA-to-RNA-to-protein system is complex! may RNA may have been first genetic material RNA can assemble spontaneously How switch from RNA to DNA might have occurred is not known The The First Cells Eon Originated in Archaean Eon There were prokaryotic cells These were heterotrophs Secured energy through anaerobic pathways No oxygen present, therefore they must have Relied on glycolysis and fermentation only! Advantages Advantages of Organelles Nuclear envelope may have helped to protect genes from competition with foreign DNA ER channels may have similarly protected vital proteins … Possible Possible Origin of ER DNA infolding of plasma membrane Theory Theory of Endosymbiosis Lynn Margulis Mitochondria and chloroplasts are the descendents of free-living prokaryotic organisms Prokaryotes were engulfed by early eukaryotes and became permanent internal symbionts http://www.sumanasinc.com/webcontent/anis amples/nonmajorsbiology/organelles.html Evolutionary Evolutionary Tree hydrogen-rich anaerobic atmosphere atmospheric oxygen, 10% archaean lineage ancestors of eukaryotes endomembrane system and nucleus cyclic pathway of photosynthesis noncyclic pathway of photosynthesis origin of prokaryotes 3.8 billion years ago 3.2 billion years ago aerobic respiration 2.5 billion years ago Evolutionary Evolutionary Tree ...
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