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BIOL 215 Notes for Midterm.doc

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Biology (Sci)
BIOL 215
Catherine Potvin

Sept 3 2009Lecture 2 Origin of Earth and LifeOrigins of Elements and Earth A chronological history of Earth46 bya origin of earth approximately4238 bya RNA world38375 bya Metabolism DNAProtein world3837 bya Origin of life3528 bya Origin of photosynthesis2520 bya Change from anoxygenic to oxygenic environment17 bya oldest eukaryotes fossils12 bya first multicellular organisms250 mya Pangaea supercontinent forms65 mya dinosaurs went extinct6 mya earliest humans Big Bang is dated 1015 byaquarks hypothetical building blocks that fuse together to form protons and neutrons which then go on to form hydrogen and helium molecules protostars are formed by nuclear fusion of hydrogen and helium atoms This reaction yielded lots of energy which created a dense core forming elements to iron while burning Once the core is composed largely of iron the protostars stop burning It had consumed most of the fuel h and he once fuel is exhausted the protostar explodes to form a supernova releasing all of the elements into space as hot gasesThe sun is createdPlanets around the sun form from gradual accumulation of solid matter called planetisismalsEarth was initially molten and composed of largely Fe Mg Si and OEarth formed 46 byaCrust forms 4241 bya as earth coolsMeteors and comets bombard Earth 4538 bya supplying lighter elements and frozen gases46 bya4241 bya40 bya37 byaEarth formscrust formscometsmeteorsoldest fossilsPrimitive Earths atmosphereGenerated by volcanic outgassing 80 and impact bodies 20CO 1001000 x greater than present N H0 222Atmosphere reducing reducing gases electron takingNO FREE O in atmosphere initiallyimportant since 0 would have 22prevented the buildup of organic moleculesVery dense atmosphere 12 bar compared with 1 bar at present Primitive Earths OceanVolatile substances such as the oceans remained in the atmosphere due to extreme heat Once earth cooled to 100C water condensed and formed oceansLarge impact bodies would have vaporized the entire ocean destroying any lifeEarth had liquid water on its surface by 38 bya sedimentary rocksLIFE AT 37 BYA in the form of Stromatalytes blue green algae cyanobacteriaoAlso in form of organic matter found in rocks C13C12 ratio indicates that life had evolved by 37 byaOnce the oceans formed all atmospheric gases will dissolve in water due to high solubilityThese acids then dissolved rocks on land by the process of chemical weathering and rivers carried these salts to the ocean making it salty and adding all elements that would be used by organismsCharacteristics of Life1Organization organs tissues organelles to carry out specific functions2Energy use and metabolism To build new structures Involves series of chemical reactions 3Homeostasis Maintains consistency of internal composition in spite of external environmentEx ionic composition of a cellmust maintain water levels and dispose of waste4ReplicationreproductionExact copy of genetic material is provided to offspring5Response to environmental stimulusEx plants bending towards lightOrigin of Building BlocksPrebiotic chemistryPreRNA worldRNA WorldDNAProtein WorldPrimordial CellOrigin of life is known through lab research on chemical reactions that may have occurred 47 byaStep 1Raw materials simple organic matter such as amino acids hydroxy acids sugars purines pyrimidines and fatty acids MillerUrey Step 2Simple organic matter is linked together into polymers with propertiesof replicationRNAStep 3Reverse Transcriptase copies RNA into DNA which replicatesStep 4RNA from DNA builds Proteins and Lipids which form spheresStep 5Compartmentalizationthe formation of an outer membrane that encased the nucleic acids and proteins Likely started with Liposomes bubbles of lipid forming a sealed sphereMillerUrey Experiment 1953The experiment used water H2O methane CH4 ammonia NH3 and hydrogen H2 The chemicals were all sealed inside a sterile array of glass tubes and flasks connected in a loop with one flask halffull of liquid water and another flask containing a pair of electrodes The liquid water was heated to
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