origins of life - 3/18/2008 Outline Origin of life...

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3/18/2008 1 Outline • Origin of life • Protists (Eukaryotes) • Putting the ‘fun’ back into fungus Where did life come from? • In history – thought that life came from non-living things- “spontaneous generation” • More recently (Pasteur): people believe life comes from life: “biogenesis” life comes from life: biogenesis • These contradict… – So where did first living things come from? – What is a living thing, anyway? Archean Eon and Earlier • ~4 billion years ago earths crust forms, atmosphere: –No O 2 – Hydrogen, nitrogen, CO, CO2 • Archaen: 3.8-2.5 billion years – First cells appear 3.8 BYA – Anaerobic bacteria • Chemical and molecular evolution The early Earth…. “atmosphere”: methane, ammonia, hydrogen sulfide water vapor Sparks simulate lightning <1 wk. Amino acids! Varying compounds- got nucleic acids! Origin of Organic Compounds • Amino acids, other organic compounds can form spontaneously under
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3/18/2008 2 The first organisms A working hypothesis: 1 st life resulted from 4 stage process: 1) Abiotic synthesis of small organic molecules 9 Amino acids (building blocks of proteins) 9 Nucleotides (building blocks of DNA) 9 1952- experiments simulated Earth ~4 BYA 9 Got generation of aminos and nucleotides! 2) These small molecules joined to form proteins 9 Also shown with lab experiments The first organisms 3) Origin of self replicating molecules (being 9 First genes were probably short strands of RNA 9 We know about self-replicating genetic elements (e.g., prions- mad cow disease) 4) Formation of pre-cells 9 Something (membrane) separates this material from outside 9 Lab experiments have made “pre-cells” too 9 Phospholipids (water repelling inside) Origin of Organic Compounds • Clay may have served as template
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origins of life - 3/18/2008 Outline Origin of life...

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