Bio20C Notes 2

Bio20C Notes 2 - Winter 2009 Biology 20C D.C. Potts BIOE...

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Winter 2009 Biology 20C D.C. Potts 1 of 1 File: 20C-W09-L.02-Origins-Notes.doc Printed: 9 January, 2009; 02:16 BIOE 20C: ECOLOGY and EVOLUTION Lecture 2 : 9 January 2009 Origins of the Environment, Life and Ecology © Donald C. Potts 1997-2009 ORIGINS of the SOLAR SYSTEM Age (Ma) (Ma = million years ago) >14000 ORIGIN OF THE UNIVERSE - “ Big Bang 13000 Origin of galaxy (“Milky Way”) > 4600 Supernovae create inter-stellar cloud of cold gas and dust (= nebula ) 4550 ORIGIN OF THE SOLAR SYSTEM Nebula collapses into a spinning disc Gravity pulls heavier elements (metals) and high melting point (refractory) minerals (silicates) inwards Center (mainly He-Xe, H, C, N, O) increases in mass and temperature until minerals vaporized Center reaches critical mass and ignites in fusion reaction Î sun Sun Î solar wind pushes lighter molecules outwards; heavy elements continue to move inwards Low velocity collisions within disc Î accretion of planetesimals (<1 km) Î asteroids 10-100km) Î protoplanets (<500km) Î planets (>1000km) 4500 SOLAR SYSTEM ESTABLISHED Sun : 99.7% of system mass; mainly light gases (He-Xe, H, C, N, O) Inner Planets (Mercury - asteroids): high density; hot; mainly metals and refractory (high melting point) minerals (Ca, Al, Fe, Mg, Si) Inner Gas Giants (Jupiter, Saturn): low density: cool; similar to sun (He-Xe, H, C, N, O) Outer Gas Planets (Uranus, Neptune): very cold; gases (H,C,N,O) and ice Pluto : high density; very cold; smallest planet; asteroid + unusual orbit? 4500 Asteroid bombardment : high velocity collisions Î heat, melting, volcanics, Î degassing Î 1 o atmosphere (CO Î reducing envir. Unsuccessful origins of life? - destroyed by subsequent cometary collisions? ? 4000
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Bio20C Notes 2 - Winter 2009 Biology 20C D.C. Potts BIOE...

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