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The History of Life Earth’s Early History
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Most Pictures In This PowerPoint Were Downloaded From:
Picture Credits Most Pictures In This PowerPoint Were Downloaded From:
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Formation of Earth Key Concept Earth’s Early Atmosphere Contained: Hydrogen Cyanide Carbon Dioxide Carbon Monoxide Nitrogen Hydrogen Sulfide Water
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Formation of Earth The Material Forming Earth Probably Condensed From Stellar Debris Over 100 Million Years Surface Originally Molten Atmosphere Pinkish-Orange &
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Condensation of Debris
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Earth’s Early Atmosphere
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Kept Earth Hot 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
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Early Crust Forms
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Formation of Earth ~3.8 Billion Years Ago Oceans Formed
Earth Cooled Enough For Water To Condense Oceans Formed Green/Brown With Iron Thunderstorms Continuous Life Appeared
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The First Organic Molecules
Atoms Do Not Assemble Into Complex Organic Molecules Today Due To: Oxygen is VERY Reactive & Bacteria would eat them
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Miller & Urey Stanley Miller & Harold Urey 1950’s - Chemists
Simulated Earths Early Atmosphere In The Laboratory Ran Electric Sparks Through It Simulating Lightning
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Miller & Urey Experiment Generated Amino Acids In Just A Few Days
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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.
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Corrected Experiments Have Produced Cytosine & Uracil
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
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How Did Life Form From The Organic Soup Of Original Earth?
How Did Life Begin? How Did Life Form From The Organic Soup Of Original Earth? Prokaryote Fossils These Fossils Date To Million Years After The Earth Cooled Enough For Water To Form
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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
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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
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Microfossils - 3.5 Billion Years Old
Free Oxygen Microfossils Billion Years Old Prokaryotes Anaerobic (No O2 In Atmosphere) Photosynthetic Bacteria Arose 2.2 Billion Years Ago O2 Continuously Released Into The Atmosphere
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First It Bound Iron In The Oceans
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
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Next O2 Accumulated In The Atmosphere
Free Oxygen Next O2 Accumulated In The Atmosphere O2 Increased Methane & Hydrogen Sulfide Decreased Atmosphere Turned Blue
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First Aerobic Organisms Arise
Free Oxygen Is Highly Reactive Deadly To Anaerobes First Aerobic Organisms Arise
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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
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Variations in CO2 and O2
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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
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Origin of Eukaryotic Cells
Began About 2 Billion Years Ago Some Prokaryotes Started Developing Inner Cell Membranes
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Origin of Eukaryotic Cells
Endosymbiotic Theory Some Smaller Prokaryotes Began Living In Larger Prokaryotes. A Symbiotic Relationship Developed Some Became Mitochondria Some Became Chloroplasts
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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
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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
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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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