Transcript Chapter 14
Chapter 14 History of the Earth Earth • If you could visit Ohio 3 bya ago what would you see? • 1 bya? • 500 mya? A Place to Stand On: survival not included • Per fossil evidence: – Earth formed ~4.6 bya, was a hot volcanic mess – ~500 my after stable crust formed Atmosphere: smells like death • Likely volcanic gas atmosphere – Ex: H2O, CO2, SO2, CO, H2S, HCN, N2, H2 – Key Point: No Oxygen! Where are the answers? • Fossil Record – Rocks date back ~4bya – First signs of life preserved ~3.5 bya – Types of fossils • Trace, Mold/cast, Replacement, Petrified, Amber, Original material How to make a fossil • Most species now extinct • To preserve best if – Aquatic (better sediment coverage) – Hard body parts – Prevalent and widespread. – Even then very few would fossilize – Need to end up in sedimentary rock/mineralize Fossil Types Dating Fossils (Mr. Kaufman) • Absolute vs. Relative – Absolute = radioactive isotopes and half-life • Several isotopes with different half-lives – Relative = by strata • Oldest at the bottom (superposition) The Geologic Time Scale • Precambian – Start of Earth (4.6bya) – paleozoic (542mya) – First life (prokes), photosynthesis, Euks, and early multicellularity • Paleozoic – Begins with Cambrian Explosion (origin of modern animal groups) – Fish, insects, and tetrapods evolve – Ends w/ Permian Extinction (251mya, ~75% extinct) • Mesozoic – Reptiles take over – Dinosaurs, then mammals, then birds evolve – Flowering plants evolve – Ends with cretaceous mass extinction (K-T Event, 65mya) – Affected by plates tectonics • Cenozoic – 65mya – present – Mammals become dominant land animal – Humans very, very recent development Origins of Life (Early) • Spontaneous generation (life from non-life) – Rotting meat created flies, broth created bacteria… – Proved wrong by Redi, Pasteur, etc. • Cheese cloth jar w/ meat and curved neck flask Biogenesis • Theory beat spontaneous generation • Life only comes from existing life • So where did the original life come from? Abiogenesis • Accounts for start of life from non-life • Hypothesis • Currently evidence suggests a “primordial soup” – Early Earth conditions allow formation of simple organics – In right conditions these form organic polymers – Organic polymers can join to become cells Evidence • Miller and Urey – Used early Earth simulator and found monomers • Fox – Used heat/clay to make proteins 1st Cells • RNA likely 1st genetic material • Likely prokaryotes • Likely related to archaea (extremophiles) – Many are chemoautotrophic – Make food w/o oxygen, sun • Prokaryote fossils go back 3.5by – Photosynthesis close to that (cyanobacteria) Eukaryotes • Endosymbiosis – Smaller prokes lived inside larger prokes – Allowed for aerobic respiration or photosynthesis – Went from mutualism to Organism/Organelle • Explains mitochondria/chloroplasts • Other organelles likely membrane infoldings Endosymbiosis