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Ch 25: History of Life 5/10/15 Ch 25: History of Life “There is nothing permanent but change.” (Heraclitus) “Chaos always defeats order because it is better organized.” (Terry Pratchett) Louis Pasteur: Disproving spontaneous generation Universe forms ~13.8 bya Early solar system formation ~ 4.5 bya 1 5/10/15 Earth’s 1st 1 billion years Moon formed by a collision Radiometric Dating Half-lives 14C: 5,730y 40K: 1.25 by 238U: 4.5 by Index fossils 2 5/10/15 Arrhenius & Mojzsis Some of the oldest fossils ~3.4 bya (Strelley Pool, Australia) organic trace fossils http://physicsforme.files.wordpress.com/ ~3.8 bya 2011/08/astrobiology3.jpg Abiogenesis: First step- compounds of life from non-living 1920s AJ Oparin JBS Haldane Miller-Urey experiment (1952/publ 1953) Stanley Miller Harold Urey 10–15% of the carbon now in the form of organic compounds 2% of the carbon had formed amino acids, with glycine the most abundant (all 20 common ones were found) (In 2008, his student J. Bada reexamined some of Fig 4.2 the vials.) 3 5/10/15 proteinoid Protobionts microspheres vesicles 4 5/10/15 Sidney Altman Thomas Cech Other possibilities for early genetic material: PNAs (Miller) Which came first? Where do the materials come from? Earth “panspermia” molecules on space rocks Note: moves some of the origin question off earth but still have the question… 5 5/10/15 Where did life begin? One hypothesis - deep, hot water Early microfossils: stromatolites Shark Bay, Australia (present day) early O2 production Banded Iron Formations 6 5/10/15 O2 production -> ! Sun Ozone (O3) shield protects us from UV ! Ultraviolet rays 3(O2)! ! Upper atmosphere 2(O )! 3 ! Lower atmosphere SBMFig. 20.06! Eukaryotes formation of organelles -> multicellularity endosymbiosis Grypania spiralis (filaments) Lokiarchaeota discovery 2015 http://phenomena.nationalgeographic.com/2015/05/06/new-loki-microbe-is-closest-relative-to- all-complex-life/ 7 5/10/15 How are organisms related? old26.21 Current trees of life (largely based on rRNA) 26.21 Horizontal gene But may not be a transfer (26.23) straightforward tree Ring of life? (old26.23) Snowball Earth 8 5/10/15 Tour: Proterozoic Era: 2.5 bya -> 542 mya Ediacaran fauna Paleozoic Era Cambrian Period 542 -> 488.3 mya all current major animal phyla have appeared Cambrian Period 542 -> 488.3 mya fossil animal embryos Burgess shale 9 5/10/15 Ordovician Period 488.3 -> 443.7 mya first plants? Silurian Period 443.7 -> 416 mya Devonian Period 416 -> 359.2 mya “Age of Fishes” 10 5/10/15 Carboniferous Period 359.2 -> 299 mya (large amounts of forest -> major coal deposits) Permian Period 299 -> 251 mya Mesozoic Era “Age of Reptiles” Triassic Period 251 -> 199.6 mya Jurassic Period 199.6-> 145.5 mya Cretaceous Period 145.5 -> 65.5 mya Fig. 20.13! 11 5/10/15 Cenozoic Era (Age of Mammals, Insects, Birds, Flowering Plants) Paleogene Period Paleocene Epoch 65.5 -> 55.8 mya Eocene Epoch 55.8 -> 33.9 mya Oligocene Epoch 33.9 -> 23 mya Cenozoic Era Neogene Period Miocene Epoch 23 -> 5 mya Pliocene Epoch 5 mya -> 1.8 mya Pleistocene Epoch 1.8 mya -> 10,000 ya Holocene Epoch 10,000 ya -> present? Anthropocene? Land changes: continental plates and plate tectonics 12 5/10/15 “Recent” continental drift Mass extinctions: 5 – 8 events (note: appear different at different taxonomic levels) Q: Is one happening now? Opportunities & changes 13 5/10/15 Development changes can change bodies Timing changes allometric growth Development changes can change bodies Timing changes paedomorphosis axolotl Development changes can change bodies Changes in genes Number of Hox genes How Hox genes are used 14 5/10/15 Evolution does not work toward a snail “goal” limpets eg: mollusk eyes – all useful Nautilus snail squids & octopi Tree of Life video clip with D. Attenborough http://www.wellcometreeoflife.org/video/ Interactive http://www.wellcometreeoflife.org/interactive/ 15 .
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