The History of Life Earth’s Early History

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Formation of Earth Key Concept Earth’s Early Atmosphere Contained: Hydrogen Cyanide Carbon Dioxide Carbon Monoxide Nitrogen Hydrogen Sulfide Water

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

Condensation of Debris

Earth’s Early Atmosphere

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

Early Crust Forms

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

The First Organic Molecules Atoms Do Not Assemble Into Complex Organic Molecules Today Due To: Oxygen is VERY Reactive & Bacteria would eat them

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

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

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.

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

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 200-300 Million Years After The Earth Cooled Enough For Water To Form

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

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

Microfossils - 3.5 Billion Years Old 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

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

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

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

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

Variations in CO2 and O2

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

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

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

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

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

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