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Earth ’ s Early History

Earth ’ s Early History

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Earth ’ s Early History

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  1. Earth’s Early History

  2. Mystery of Life’s Origins • Using radiometric dating, scientists believe the Earth to be between 4.2 and 4.6 Billion Years Old. • Earth’s early atmosphere contained little or no oxygen. • Made up of mostly: CO2, water vapor, and nitrogen

  3. How did Life Begin? • 3 ideas of how life may have gotten on Earth • Divine Creation – a higher being put us here on Earth • Extraterrestrial Origin – life may have come to Earth via an asteroid or meteorite. • Spontaneous Origin – process through which life is thought to have developed when molecules of non-living matter reacted chemically during the 1st billion years.

  4. Spontaneous Origin • 1920’s A.I. Oparin – Primordial Soup Model • Oceans were a big soup bowl with large amounts of organic molecules • Chemical reactions spontaneously occurred in soup with energy from lightning/volcanoes • Proposed that Earth’s early atmosphere lacked oxygen, yet had plenty of nitrogen, hydrogen, water vapor (earth was hot), methane and ammonia.

  5. Stanley Miller • 1953, tested Oparin’s hypothesis • Placed gases in apparatus, zapped it, and found some basic chemicals could have formed spontaneously • 2 problems • Too slow • Not sure methane and ammonia was available, and if it was, UV would destroy it

  6. Louis Lerman • 1986 – Bubble Model • Chemical reactions took place in the bubbles of the ocean • Reactions would take place faster in bubbles • Inside bubbles, methane and ammonia protected from UV rays • Leading hypothesis accepted to date

  7. Origins of Eukaryotic Cells • Endosymbiotic Theory – proposes that a symbiotic relationship evolved over time, between primitive eukaryotic cells and the prokaryotic cells within them. • Ex. Mitochondria and Chloroplasts are thought to have been ancient prokaryotes • Both have their own DNA, ribosomes and both reproduce by binary fission like bacteria cells