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BIO1130 midterm 1 notes - Hadean & Archean Eons1.docx

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Hadean and Archean EonsGeological Time Scale Major Eons Hadean and Archean this unitHadean 46003800 MaFormation of solar system and planet ends off with origin of lifeArchaean 38002500 MaAnaerobic bacterial life oxygen starts to accumulate in atmosphere Archealive in extreme conditionsProterozoic 2500543 MaOxygen atmosphere single celled aerobic organismsPhanerozoic 543 Ma to PresentMulticellular organismsHadean EonBuilding PhaseMeteorites that contained lots of minerals C H O crashed into Earths surface and provided it with the basic building blocks of lifeAt this point Earth is still a molten ball and meteorites are still flying into it on a regular basisStabalizing PhaseEarth starts to develop a crust on top of the molten lavaEarth is unique in which its mass is able to hold in an atmosphereso it could trap in the molecules needed to surviveThe water vapour in the air starts to cool down and water starts to accumulate on the Earths surface which formed the oceans However if another meteorite strikes then the water is Vapourized Evaporation because of the intense amount of heat created by the impact and the cycle starts over againMeteorites stopped hitting the Earth at the end of Hadean EonPanspermia Life came from extraterrestrial origins No conclusive arguments bacteria came from meteorites to EarthWe still dont know WHERE exactly life came fromHypothesis that proposes life on Earth was transferred from elsewhere in the Universe CarbonAll life on earth is carbonbased Silicon has the same properties as carbon and somewhere in the universe there might be a whole parallel forms of life all based on silicon instead of carbonSilicon used in computer chips here on EarthCarbon is the ideal lego block for building larger structures organisms This is because carbon is a perfectly symmetrical element tetrahedral orientation of its electronsAdhesionWater sticks to other objectsThe adherence of molecules to the walls of conducting tubes as in plantsExplains the meniscus you see in test tubes etcCohesionThe high resistance of water molecules to separationWater has a high tendancy to stick together due to polar characteristicsSurface tension is an example of cohesionSurface Tension
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