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Hadean and Archean eons.docx

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Hadean and Archean eonshttpsalinellabiouottawacaBIO1130Lecturesdefaultphp1130lect04HadnSallphpEMd2ChapterMcp1IntroductionThe earth is about 4500 million years old multicellular life arose 500 million years agoFour main eonsoPhanerozoic 543 Ma to present time multicellular organismsoProterozoic 2500543 Ma Oxygen atmosphere single celled aerobic organismsoArchaean 38002500 Ma mostly anaerobic bacterial life oxygen accumulatesoHadean 460038 00 Ma formulation of solar system and planet ends with origin of lifeEons are made up of ErasPhanerozoicoCenozoic 65 Ma to present timeoMesozoic 25165 Ma Dinosaurs Wooh I thinkoPaleozoic 543251 Ma at 550 or so Cambrian explosionHadean Eon create oContinuous bombardment creating molten planet comets helpoceans among other thingscools planet solidifying the crustoLightningvolcanic gases created prebiotic soup supplemented by deep sea hydrothermal vents and meteorite materials leads to simple organic compounds ie carbonoStill cant be explained how DNA and RNA first came nucleotides still cant be synthesized or how first biopolymers appearedGeological time scaleEarly paleontologists couldnt accurately measure the periods based on sedimentary rock because of lack of technologyModern paleontology radioactive decay gives much accurate estimations However is still hard to comprehend because of the magnitude of years billionsAlthough paleontologists likened to categorizing the periods into different eons it ignored some contributions that would be happenings overtime within the periods overall contributions of the archaea and the first unicellular protists to the changes in the planet not being part of the Precambrian period Biologists saw this error of point of viewCambrian explosion 550 Ma odiversification of animal life in oceans feeding on protistso Some life move onto land than global catastrophe kills off 90 of marine lifeMesozoic 24565 Ma o many animal life perfect and evolve on land new species replace marine life global diversity comes back oAs Mesozoic ends dinosaurs die age of reptiles end another global catastrophe many land animals die
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