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Lecture 3

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Simon Fraser University
Biological Sciences
BISC 110
Robin Barrow

Lecture 3- The origin of life on Earth Readings: Chapter 25, pp. 507-510 Concept 25.1 Life •metabolism •nutrient uptake •nutrient processing •waste elimination •generative processes •growth and reproduction (replication) •responsive processes •immediate response to environment •individual adaption •population evolution •control processes •coordination •regulation •product •structural organization •cellular level •organismal level Ideas change as scientific evidence accumulates •sun revolves around earth •earth is flat First idea of the origin of life: spontaneous generation •Aristotle: 'living organisms arise spontaneously from non-living matter” •Evidence: •maggots are formed from dead meat •mice develop in the dark from wheat seeds •lice are made from sweat •frogs are made from the damp mud •BUT: Louis Pasteur: 'life can only originate from pre-existing life' •BUT: Lynn Margulis: 'if live can originate from pre-existing life, then how did the first living things arise?' •'to go from bacteria to people is less of a step than to go from a mixture of amino acids to a bacterium' Timeline of Earth •Big Bang: 15 bya (billion years ago) •Earth formed: 4.7 bya •Stable crust of the Earth: 3.9 bya •Life on Earth: 3.6-3.7 bya Recipe for life •energy source + Raw materials + suitable environment Conditions on early Earth •Earth and other planets were formed from condensing vast clouds of dust and rocks •no organisms because Earth still had big chunks of rocks and ice left over (the collision generated enough heat to vaporize the water, preventing seas from forming) •extremely HIGH temperature •different atmosphere (these were high in early earth) •lots of water vapour! •Compounds produced from volcanic eruptions: •Nitrogen •CO2 •Methane •Ammonia •Hydrogen •Hydrogen Sulfide •no liquid water •little oxygen •as Earth cooled: •high UV •water vapour condensed •hydrogen escaped •these conditions were bad for some organisms but some adapted by using respiration Energy sources •Sun (light, UV) •Volcanic eruptions, lightning Raw materials •Elements on earth •C, H, N, O, P, S •extraterrestrial sources •introduced by Arrhenius in early 1900s •evidence: •Murchison meteorite containing amino acids •ALH 84001 meteorite: Martian bacteria •there only a few extraterrestrial sources introduced on earth •scientists focus on what kind of organic compounds are in these materials (such as amino acids and nucleobases [basic building blocks of life] Local Sources(Origin of life on Earth by chemical evolution: how the first living cells appear) •Through Chemical and Physical conditions •Stage 1: Abiotic synthesis of monomers (organic molecules such as amino acids and nitrogenous bases) •Introduced by Al Oparin and JBS Haldane •Hypothesis: reducing atmosphere + simple molecules (from thunder, sun: high UV...or meteorites) combine into organic compounds ? forms a suitable environment for life •Testing their hypothesis, experimented by Stanley Miller and Harold Urey •in a tube, water is heated ? water vapour rises ? from electrodes,
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