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Introduction to Evolution Earth History Origin of Life Central Questions • What was the early Earth like? • What were the first cells like? • What is the Endosymbiotic Theory? • What is spontaneous generation? What experiments were used to disprove it? Early Earth • Earth was formed approximately 4.6 billion years ago • It was covered in boiling oceans, volcanoes, storms and a poisonous atmosphere that contained no oxygen Starting Life • Where would the first organic molecules come from? • Alexander Oparin hypothesized that life could come from Chemical Evolution • Miller and Urey passed electricity through a simulation of the early atmosphere and made organic compounds. Early Life • Earliest fossils are about 4 billion years old- simple prokaryotic cells (bacteria) • They were anaerobic (didn’t use oxygen) heterotrophs that fed off of organic compounds (remember no oxygen or photosynthesis) More Complex Life • Mutations over time lead to the development of photosynthesis and more oxygen in the atmosphere (equation for photosynthesis ) • Endosymbiont theory larger cells absorbed cells that could photosynthesize or use oxygen to break down food, making the first eukaryotes Endosymbiont theory General Timeline of Evolution • • • • • 4.54 BYA 4 BYA 4 -3.8 BYA 3.5 BYA 2.4 BYA • 1.7 – 1.2 BYA Formation of the Earth End of Heavy Bombardment First Life Photosynthesis Oxygen rich atmosphere Eukaryotes Multicellular Life Plants Fungi Sexual Reproduction • 1 B - 580 MYA • 530 MYA • 490 MYA • • • • • • 370 MYA 300 MYA 250 MYA 230 MYA 200 MYA 180 MYA Animals Cambrian Explosion Land Plants Land invertebratess Land vertebrates Pangaea forms P-TR Extinction (biggest) Dinosaurs Tr-J Extinction Pangaea breaks up • 150 MYA • 130 – 90 MYA • 65 MYA • • • • 6 MYA 2.5 MYA 200 KYA 100 KYA Avian evolution Angiosperms Social Insects K-T Extinction (dinosaurs die off, mammals emerge) Great Apes Diverge Stone tools Human migration “Great leap forward” Spontaneous Generation • Spontaneous Generationidea that life came from nonliving material, like maggots from dead meat • Also called abiogenesis (beginning from no life) • Incorrect theory, how might you disprove it? Experiments • Francisco Redi (1668)- Put meat under a lid to prove no maggots would grow (disprove spontaneous generation) Louis Pasteur (1861)- Used Sshaped flasks to finally disprove spontaneous gen. • Spontaneous Generation was finally proven wrong by Pasteur’s experiments • Science supports the idea of biogenesis. Bio=life, genesis=beginning • Biogenesis- life comes from other life (like the cell theory) Central Questions • What was the early Earth like? • What were the first cells like? • What is the Endosymbiotic Hypothesis? • What is spontaneous generation? What experiments were used to disprove it?
