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Lecture 2 Time scales 1 The formation of the earth 2 Measuring time on Earth 3 A brief tour through the history of time on Earth Origin of life 1 Extra terrestrial origins 2 What is life 3 The Earth before life originated 4 Four steps 9 1 2021 Time scales An artist s impression of the protoplanetary disk Perturbations in the outer rings of the disk become protoplanets Time scales Time scales An artist s impression of the birth of the sun An artist s impression of the formation of the earth Pressure within the central mass of the protoplanetary disk triggers nuclear fusion Gravity outside the reach of the sun causes matter to condense around protoplanets 1 2 4 1 3 Time scales There are four main time periods in the Earth s history that I want you to know Precambrian supereon 4 6 BYA 543 MYA Paleozoic era 543 MYA 250 MYA Mesozoic era 250 MYA 65 MYA Cenozoic era 65 MYA now Time scales How we divide time Holocene epoch now Too small to fit on scale Time scales Time scales How we divide time from your text An artist s impression of the Hadean eon 5 7 6 8 9 1 2021 2 Time scales Time scales An artist s impression of the late Hadean eon The Hadean eon ends with the first life between 4 2 and 3 8 BYA 9 1 2021 It s getting a bit better Vertical sections through fossil stromatolites Modern stromatolites in Australia Figure 23 9 9 Time scales 10 Time scales More modern stromatolites in Australia Multicellular life arises late in the Precambrian 1 BYA 11 12 Trace fossil indicates movement Fossils of Precambrian multicellular life 3 Time scales Time scales The Paleozoic Era 543 MYA 250 MYA The Paleozoic Era 543 MYA 250 MYA Rare trilobite fossil with intact eyestalks Lateral and dorsal trilobite fossils 13 Time scales Reconstruction of the Burgess Shale Animals from the supposed Cambrian explosion Archaeocyatha various Cambrian sponge like animals called Archaeocyathids 14 Time scales Carpet moss Early amphibian tetrapod The Cambrian explosion Probably not such a big bang The Paleozoic Era sees the first land plants and animals 15 16 The first portion of the Paleozoic Figure 23 14 9 1 2021 4 9 1 2021 Figure 23 14 Time scales Time scales The Paleozoic Era ends with the Permian extinction The Mesozoic Era 250 MYA 65 MYA Age of reptiles Figure 23 14 Early dinosaur The second portion of the Paleozoic 17 Time scales 18 Time scales The Mesozoic Era The first mammals The Mesozoic Era ends with the K T extinction Artists impression of impact event Artist impressions of Morganucodon watsoni Appeared around 205 MYA 19 20 A K T boundary 5 Time scales Time scales The Cenozoic Era 65 MYA now Age of mammals The Earth itself has changed over time Crazy artist s rendition of age of mammals Mid Paleozoic Early Mesozoic Modern era Early Paleozoic Late Paleozoic Late Mesozoic 22 Time scales Geologic clocks help us re visualize the passage of time KT extinction Figure 23 14 21 Time scales Check it out in animation Linked through Achieve 7 minutes 23 24 9 1 2021 6 Origin of life Origin of life What happened 3 8 billion years ago 25 Origin of life Life has two characteristics 1 Organized 2 Replicates itself An artist s impression of panspermia 26 Origin of life What was Earth like 3 8 BYA Molten rock No free oxygen reducing atmosphere High energy environment In this environment the formation of life probably requires four steps 27 28 9 1 2021 7 9 1 2021 The importance of clay Clay Rich in Iron Fe and Zinc Zn Origin of life Origin of life 1 Abiotic synthesis of organic materials 2 Formation of polymers Within one week Amino acids Nucleotides Sugars Lipids ATP Fig 4 10 29 Origin of life 30 Origin of life 3 Formation of protobionts 4 Origin of hereditary material The first life probably existed in an RNA world The structure of RNA 31 32 8 Origin of life Origin of life Why an RNA world Viroids may be clues to the RNA world Normal Infected 1 Easily forms abiotically 2 Can replicate itself 3 Has hereditary information 4 Has catalytic properties 33 Origin of life So when exactly does this become life 34 Origin of life What formed 3 8 BYA resulted in all the diversity that followed it 35 Hug et al 2016 36 9 1 2021 9

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UB STA 301 - Lecture 2

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