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Chapter 17 Section 3 Evolution of Multicellular Life

Chapter 17 Section 3 Evolution of Multicellular Life. Objectives: -Describe the key forms of life in the Paleozoic, Mesozoic, and Cenozoic eras. What has been learned from fossils. Several episodes of mass extinction that fall between time divisions

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Chapter 17 Section 3 Evolution of Multicellular Life

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  1. Chapter 17 Section 3Evolution of Multicellular Life Objectives: -Describe the key forms of life in the Paleozoic, Mesozoic, and Cenozoic eras

  2. What has been learned from fossils • Several episodes of mass extinction that fall between time divisions • Mass extinctionan event that occurs when many organisms disappear from the fossil record almost at once • The geologic time scale begins with the formation of Earth about 4.6 billion years ago.

  3. Precambrian – 87% of history • Oldest fossils about 3.4 billion years old resembling cyanobacteria stromatolites. • Stromatolites still form today in Australia from mats of cyanobacteria. • The stromatolites are evidence of the existence of photosynthetic organisms on Earth during the Precambrian. • Only prokaryotic life found in fossil record

  4. End of Precambrian – 543 MYA • Multicellular eukaryotes, such as sponges and jelly-fishes, diversified and filled the oceans

  5. Paleozoic and Cambrian Period • Paleozoic Era: more animals and plants • Early: fishes, aquatic vertebrates, ferns • Middle: amphibians • Late: reptiles and mass extinction • Cambrian Period: oceans teemed with many types of animals, including worms, sea stars, and unusual arthropods, trilobites

  6. Mesozoic - 248 MYA • Triassic Period: mammals and dinosaurs • Jurassic Period: dinosaurs and birds • Cretaceous Period: more mammals, flowering plants, but mass extinction of dinosaurs 65 MYA

  7. Chixulub Impact Event • Texas K-T Boundary

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