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The History of Life

The History of Life. Earth’s Early History. Picture Credits. Most Pictures In This PowerPoint Were Downloaded From:. Formation of Earth. Key Concept Earth’s Early Atmosphere Contained : Hydrogen Cyanide Carbon Dioxide Carbon Monoxide Nitrogen Hydrogen Sulfide Water. Formation of Earth.

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The History of Life

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  1. The History of Life Earth’s Early History

  2. Picture Credits Most Pictures In This PowerPoint Were Downloaded From:

  3. Formation of Earth Key Concept Earth’s Early Atmosphere Contained: Hydrogen CyanideCarbon DioxideCarbon MonoxideNitrogenHydrogen SulfideWater

  4. Formation of Earth The Material Forming Earth Probably Condensed From Stellar Debris Over 100 Million Years Surface Originally Molten Atmosphere Pinkish-Orange &

  5. Condensation of Debris

  6. Earth’s Early Atmosphere

  7. Formation of Earth ~4 Billion Years Ago Earth Cooled Enough For A Crust To Form Volcanic Activity Constant Comet & Asteroid Hits Constant Kept Earth Hot

  8. Early Crust Forms

  9. Formation of Earth ~3.8 Billion Years Ago Earth Cooled Enough For Water To Condense Oceans Formed Green/Brown With Iron Thunderstorms ContinuousLife Appeared

  10. The First Organic Molecules Atoms Do Not Assemble Into Complex Organic Molecules Today Due To: Oxygenis VERY Reactive& Bacteriawould eat them

  11. Miller & Urey Stanley Miller & Harold Urey 1950’s - Chemists Simulated Earths Early AtmosphereIn The Laboratory Ran Electric Sparks Through It Simulating Lightning

  12. Miller & Urey • Experiment Generated Amino Acids In Just A Few Days

  13. Miller & Urey Key Concept Miller & Urey’s Experiments Suggested How Mixtures Of The Organic Compounds Necessary For Life Could Have Arisen From Simpler Compounds Present On A Primitive Earth.

  14. Modified Miller & Urey Original Atmospheric Components Not Accurate(Re-Analysis of Chemical Composition of Early Rocks) Corrected Experiments Have Produced Cytosine & Uracil Two RNA Bases

  15. How Did Life Begin? How Did Life Form From The Organic Soup Of Original Earth? Prokaryote FossilsThese Fossils Date To 200-300 Million Years After The Earth Cooled Enough For Water To Form

  16. Formation of Microspheres • Proteinoid Microspheres • Large Organic Molecules Naturally Form Tiny Bubbles • Not Cells But Have Some Characteristics Of Living Systems • e.g. Selective Permeable Membranes

  17. Evolution of RNA & DNA • Still Unknown However: • RNA Sequences Have Been Found That: • Help DNA Replicate • Transcribe DNA • Translate Proteins • Catalyze Chemical Reactions • Duplicate Themselves • Perhaps RNA Came First

  18. Free Oxygen Microfossils - 3.5 Billion Years Old • Prokaryotes • Anaerobic (No O2 In Atmosphere) • Photosynthetic Bacteria Arose • 2.2 Billion Years Ago • O2 Continuously Released Into The Atmosphere

  19. Free Oxygen First It Bound Iron In The Oceans • Iron Oxides Settled To The Bottom Of The Oceans • Formed Great Bands Of Iron That We Mine Today • Oceans Changed Turned Blue

  20. Free Oxygen Next O2 Accumulated In The Atmosphere • O2 Increased • Methane & Hydrogen Sulfide Decreased • Atmosphere Turned Blue

  21. Free Oxygen Is Highly Reactive Deadly To Anaerobes First Aerobic Organisms Arise

  22. Free Oxygen Key Concept The Rise Of Oxygen In The Atmosphere Drove Some Life Forms To Extinction, While Other Life Forms Evolved New, More Efficient Metabolic Pathways That Used Oxygen For Respiration

  23. Variations in CO2 and O2

  24. Variations in CO2 and O2 C = Cambrian O = Ordovician S = Silurian D = Devonian C = Carboniferous P = Permian Tr= Triassic J = Jurassic K = Cretaceous T = Tertiary “0” on time scale = Today

  25. Origin of Eukaryotic Cells • Began About 2 Billion Years Ago • Some Prokaryotes Started Developing Inner Cell Membranes

  26. Origin of Eukaryotic Cells • Endosymbiotic Theory • Some Smaller Prokaryotes Began Living In Larger Prokaryotes. A Symbiotic Relationship Developed • Some Became Mitochondria • Some Became Chloroplasts

  27. Origin of Eukaryotic Cells Key Concept: The Endosymbiotic Theory Proposes That Eukaryotic Cells Arose From Living Communities Of Prokaryotic Organisms First Proposed 100 Years Ago

  28. Origin of Eukaryotic Cells • Lynn Margulis – Boston U. 1960’s • Evidence • Mitochondria & Chloroplasts Contain DNA & Ribosomes Similar To Bacterial DNA & Ribosomes • They Reproduce By Binary Fission

  29. Sexual Reproduction & Multicellularity • Shortly After Forming Multicellular Organisms Sexual Reproduction Began • Accelerated Development of Genetic Variation • A Few Hundred Million Years Later, Multicellular Organisms Arose And Exploded

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