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Chapter 2

Chapter 2 - Origins of Life.docx

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Athabasca University
BIOL 204
Dr.Roland Treu

CHAPTER 2 ORIGINS OF LIFE21 What is LifeAt mol level diff btwn biotic and abiotic is a blur oLiving cells obey same fundamental laws of chem and physics as does abiotic21a Seven Characteristics that All Forms of Life Share1Display order eg w cell being fundamental unit of life2Harness and utilize energy3Reproduce4Respond to stimuli 5Exhibit homeostasis6Growth and development7Evolve Example Is a virus aliveoAlthough they contain NAs they lack cellular machinery to synthesize own proteinsoEssentially they hijack machinery and metabolism of other living cellsoTF most scientists dN consider a virus alive21b The Fundamental Unit of Life is the CellCell theoryiAll organisms are composed of 1 cellsiiThe cell is the smallest unit that has the properties of lifeiiiCells arise only from the growth and division of preexisting cells22 The Chemical Origins of Life22b Conditions on Primordial EarthEvidence firmly established that Earth the Sun and other planets of solar sys all formed at abt the same timeOnce Earth was formed early hist marked by bombardment of rock from stillforming solar sys and extensive volcanicseismic activityoEst 500M yrs for Earth to cool to temps able to nurture dvlpmt of lifeOparinHaldane hypothesis 1920s these scientists proposed tht organic mols essential to formation of lifeAas sugars NT bases could have been made in absence of lifenoEarly atmosphere was a reducing atmosphere bc of presence of large concens of mol such as nH methane and ammoniarich source of electrons easily donated to make reacs possibleoWhereas today oxidizing atmosphere where O prevents formations of complex electronrich mol222c The MillerUrey ExperimentLack of O in primordial atmosphere meant no ozone layer O to partially block UV23oHypothesized tht UVabundant lightning provided energy for building blocks reqd for life1953 Stanley Miller lab simulated reducing atmosphere believed to have existedoPlaced H methane ammonia and water vapour in closed apparatus and exposed gases to energy source in form of continuously sparking electrodesResults large assortment of organic cmpds in water including urea AAs and lactic formicacetic acids23d The Synthesis of Polymers from Monomerswo sophisticated enzymes scientists h polymer of 50 monomers sufficient length to impart specific fn or 0store specific info to make their formation advantageous to an organismodoubtful polymerization could have occurred in aqueous env as they would have quickly broken downoalt H solid surfaces especially clays provided unique env for polymerization to occuro22e Protobionts The First Cellsprotobiontgroup of abiotically produced organic mol surrounded by membrane or membranelike structuredvlmpt important bc allowed for int env to dvlp distinct from ext env
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