Ch. 17 SG - Chapter 17: The Atmosphere 17.1 Earths Early...

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Chapter 17: The Atmosphere 17.1 Earth’s Early Atmospheres Earth’s primordial atmosphere was composed almost entirely of hydrogen and helium, but these gases rapidly boiled into space and escaped because we are relatively close to the Earth and the gravitational force is relatively weak. Outgassing— the release of gases from the interior of the Earth Earth’s core is the deepest layer of the geosphere When gases react with rock, the reactions not only change the chemical composition of the rocks, they also alter the composition of the atmosphere. Earth is a system. Rocks affect the air; air affects the rocks. 17.2 Life, Iron, and the Evolution of the Modern Atmosphere The first living organisms may have formed by accretion of complex abiotic (nonliving) organic molecules. Photosynthesis — the ability of plants to harness the energy in sunlight & produce organic tissue; they convert carbon dioxide & water to organic sugars and release oxygen as a bi-product; foundation for virtually all modern life Gaia— (Greek for earth) James Lovelock theorized that the oxygen created by primitive organisms slowly collected to create the modern atmosphere. He used this term to emphasize the interconnectivity of all Earth’s systems. Cyanobacteria—
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This note was uploaded on 02/13/2011 for the course ESC 1000 taught by Professor Staff during the Fall '08 term at University of Florida.

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Ch. 17 SG - Chapter 17: The Atmosphere 17.1 Earths Early...

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