Ch 17- History of Life - PowerPoint PPT Presentation

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Ch 17- History of Life

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  1. Ch 17- History of Life • Paleontologists- scientists who study fossils • Fossil record- arrangement of fossils from oldest to most recent • Provides history of life on Earth • Shows how organisms have changed • Extinct- species died out • 99% of all species have become extinct • How do fossils form?

  2. Relative dating- age of fossil in relation to fossils in other rock layers • Index fossils- fossil used to compare relative ages of fossils • Widespread, distinct, existed for short period of time • Radioactive dating- use of half-lives to determine age of sample • Calculate age of sample based on amt of remaining radioactive isotopes it contains • What is carbon dating? • Half-life- length of time required for half of radioactive atoms in sample to decay

  3. Geologic Time Scale • Precambrian Time- makes up 88% of Earth’s history • Few multicellular fossils exist from this time • Basic unit of geologic time scale after Precambrian Time are eras and periods • Paleozoic Era- 544-245 mya • Mesozoic Era- 245-65 mya • Cenozoic Era- 65 mya to present • Periods are named for places where geologists first described rocks and fossils

  4. Sec 2- Earth’s Early History • Early Earth experienced volcanic activity, bombardment by comets and asteroids, and an atmosphere of poisonous gases • Hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide and water • Stanley Miller and Harold Urey- produced amino acids by passing sparks through mixture of hydrogen, methane, ammonia, and water • Concepts in Motion • What did this suggest? • Showed how simple compounds found on early Earth could have formed organic compounds needed for life

  5. Ancient photosynthetic organisms produced a rise in oxygen in Earth’s atmosphere • Stromatolites- ancient fossil made by cyanobacteria • Drove some life forms to extinction, some evolved that used oxygen for respiration • Origin of eukaryotic cells- endosymbiotic theory- eukaryotic cells arose from living communities formed by prokaryotic organisms • Sexual reproduction speeds up evolutionary change

  6. Sec 3- Evolution of Multicellular Life • Paleozoic Era- rich diversity of marine life • “Cambrian Explosion”- braciopods and trilobites • Ordovician and Silurian Periods- 1st land plants and vertebrates • Devonian Period- Age of Fishes • Carboniferous and Permian- ancient plants form coal deposits • Mass extinction at end of Paleozoic- 95% of life

  7. Mesozoic Era • Age of Reptiles • Flowering plants • Triassic Period- mammals first appear, 1st dinosaur • Jurassic Period- dinosaurs dominate • Cretaceous- Tyrannosaurus rex dominates, new plant species • Mass extinction- half of all plant and animal, all dinosaurs

  8. Cenozoic Era • Mammals evolved- allowed them to live on land, water, air • Age of Mammals • Continental glaciers advanced and retreated several times • Fossil record suggests our species appeared 4.5 million yrs ago- did not look entirely human • Homo sapiens- appeared 200,000 yrs ago in Africa

  9. Sec 4- Patterns of Evolution • Macroevolution- large scale evolutionary patterns and processes that occur over long periods of time • Patterns of macroevolution • Extinction • Adaptive radiation • Convergent evolution • Coevolution • Punctuated equilibrium • Changes in developmental genes

  10. Adaptive Radiation-process in which species evolves into several different forms that live in different ways • Convergent Evolution- process in which unrelated organisms independently evolve similarities adapting to environment • Coevolution- process by which two species evolve in response to changes in each other • Punctuated Equilibrium- pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change • High School Biology Resources • Developmental genes and body plans- guide development of major body structures • Small changes in activity of control genes can affect many other genes to produce large changes in adults