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The history of life on Earth first _______ 200,000 years ago 30 sec before midnight first __________ organisms Origin of Earth _____________ 24 22 4.6 0.4 first _______ organisms 18 3 4 4 3.8 1 Billions of years ago 2 14 first __________ _____________ History of Earth 13.7 b.y.a. ________ Explosion of ______ Explodes out into nothing Creates _____ – the universe Cooling energy forms _______ particles Clouds of Hydrogen and Helium atoms form _____ Within stars, gravity joins particles into _____ atoms stellar nebula 5 b.y.a. Large star explodes A __________ Spews out matter 4.5 b.y.a. Gravity condenses matter into swirling cloud Becomes early ______ system ___ condenses and lights up Matter orbiting the sun gathers into ____________ One becomes Earth 4 b.y.a. Earth is bombarded by remaining matter Some meteorites contain _______ Earth becomes molten from pressure & radioactivity Heavy iron and nickel sink to core Lighter _______ floats on surface Earth cools Water vapor condenses into “primordial” seas Surface ______ develops Crust breaks up into _________ Early atmosphere is mostly N, CO2, & H2O Spewed from _________ Molecular evolution Complex molecules evolved before life 1: Organic monomers by abiotic synthesis: Miller & Urey (1950s) “_____________” Experiments Prove ______ synthesis of molecules was possible Simulate Precambrian atmosphere in tubes Early atmosphere was mostly volcanic vapors: H2O,CO,CO2,N2,CH4(methane), NH3(ammonia) Many are toxic to modern life Gaseous oxygen (O2) was _____ Electrode (__________) H2O CH4 __________ NH3 Water vapor H2 Cooling/condensation ______ H 2O tap Flame (_____________ heat) - ______________ ______________ ______________ ______________ ______________ Process can’t occur in today’s atmosphere Oxygen ______ compounds, monopolizes them Many organic monomers also occur in _________ Primordial soup may have been seeded from __ 2: : Organic polymers by abiotic synthesis Fox’s “______________” experiments Amino acids bond together on ___________ E.g., Ancient ____ flows at sea’s edge = Dehydration synthesis 3: Information molecules - _________ acids RNA __________ developed in the primordial soup May have bonded on _________ surfaces E.g., charged areas of primordial _____ Occurs in test tubes Mechanism for nucleic acid ____-replicating developed Early RNAs could have been _______-like Catalyzed necessary reactions Some modern RNA nucleic acids are _______-like 4: Cell-like spheres form around RNA E.g., Add lipids to water in a test tube Form bubble-like ____________ Membrane made of ______ 5: RNA inside becomes template for _____ synthesis Simple form of ____________ No ribosomes or tRNA yet Spheres are “____” at this stage of development 6: Novel proteins allow increasingly ________ cells Cells that replicate efficiently become more _____ Beginning of Darwinian ______ selection 7: First _______ evolve Non-living nucleic acid (information) in ______ coat ______ replication mechanism of early cells First cellular life ~ ____ bya Had traits attributable to all ‘living’ things: a) Maintained unique environment inside membrane b) Controlled the passage of ____________ c) Processed ______ (metabolism) d) Grew and reproduced e) Responded to external ________ f) Passed genetic information to daughter cells Later life-forms occurred in waves 4 major Eras: major changes in fossil biota Changes resulting from dramatic geological change GEOLOGICAL TIME SCALE 1) Precambrian: before Cambrian proliferation (1st 4 bill yrs) Mostly lifeless, ends with ___________________ animals 2) Paleozoic: “ancient” (~250->500 mya) Begins with _________ diversity & ______ (Cambrian Period) Ends with first ________ and ________ plants 3) Mesozoic: “middle” (~65->250 mya) Begins with first _______ and ___________ Ends with first ____________ plants, extinction of ________ 4) Cenozoic: “recent” (< 65 mya) Begins with radiation of mammals, birds, flowering plants Ends? A new epoch has been proposed, the ____________