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EARTH’S HISTORY Earth Forms • 4.6 billion years ago • Started out as a hot ball of lava • As it cooled the crust formed Oldest piece of rock ever found • 4.4 billion years old • Found in Australia • Zircon crystals First evidence of life • 3.5 billion years ago • Prokaryotes: Archaea and bacteria First fossils of Algae and Bacteria • Cyanobacteria or “blue green algae” • May have formed stromatolites Free Oxygen in the atmosphere • Cyanobacteria went through a process called photosynthesis. This is where carbon dioxide is converted into oxygen • 21 percent of our atmosphere is made of oxygen First fossil of complex organism • Eukaryotic cells • 1.8 billion years ago First abundant life found on fossil record • 540 million years ago • Cambrian Explosion • Major diversification in life forms appeared First Fish • Jawless fish • 520 million years ago First Land Plants • 482 million years ago • Very simple plants that lacked stems and roots such as liverworts First Land Animals • Tetrapods- animals from the sea use their front legs as crutches to pull themselves around. • 360 million years ago Largest Mass Extinction • 250 million years ago • 90 percent of all species perished • May have been due to the volcanism of the Siberian Traps First Dinosaurs • 230 million years ago • They started out small and then grew in size Pangea splits • 175 million years ago • The plates began to pull apart • This has been a cycle over the last billion years First Mammals • 160 million years ago • A shrew like creature • Was life hard living with dinosaurs? First Flowering Plants • 140 million years ago • Highly diversified (250,000 species) and they had great success covering more ground than earlier plants Dinosaurs go Extinct • 65 million years ago • The dinosaurs died out along with 50 % of the other life forms on Earth • A meteor impact in the Gulf of Mexico • Traces of Iridium are found at a distinct layer around the world Mammals and flowering plants flourish • 60 million years ago • Mammals begin to grow in size • Flowering species diversify even greater using their mammal friends to carry seeds to new areas Beginning of Cascade volcanic arc • 37 million years ago • Along the coast of Western coast of North America • The North American plate and the Juan De Fuca plate slam together at a snails pace First primate in genus Homo • 2.3 million years ago First Homo Sapien • 100,000 years ago Human inhabit North America • 60,000 years ago • Land bridge End of Last Ice Age • 11,700 years ago