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What is a fossil?

Learn about fossils and how they provide evidence of past events, show correlations between rock layers, and give clues about organisms that lived long ago. Discover the different types of fossils and their formation processes.

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What is a fossil?

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  1. What is a fossil? • A fossil is the preserved remains of a once-living organism.

  2. What do fossils tell us? • 1. help scientists determine the age of the earth • Biodiversity

  3. A half-life is the amount of time it takes for half of the atom to decay. • Scientists know how long it takes for these atoms to decay. • Radiometric dating measures how much certain atoms have decayed in the fossil

  4. LAW OF SUPERPOSITION the oldest layer is on the bottom and the youngest is on top- fossils are older in the lower layers

  5. What do fossils tell us? • 2. give clues about organisms • that lived long ago, • relationships and how • they have changed over time • Biodiversity

  6. Homologous structures Commonalities found in different organisms that show ancestry

  7. Behaviors • Nests • Egg laying • Herds • Caring for young • Predation

  8. What do fossils tell us? 3. provide evidence about past events (asteroids, volcanoes, ice ages) Biodiversity

  9. What do fossils tell us? • 4. show correlations between rock layers from around the world providing evidence of continent movement • Biodiversity

  10. What do fossils tell us? • 5. provide evidence and • clues for the geological time scale • Biodiversity Geological Time Scale: a series of time intervals that divides Earth’s history based on specific events like mass extinctions

  11. Petrified Fossils Molds and Casts CarbonFilms Trace Fossils Preserved Remains FIVE MAIN TYPES OF FOSSILS 1 2 3 4 5

  12. PETRIFIED FOSSILS http://www.dailymotion.com/video/x2mh2ie PETRIFIED FOSSILThe Field Museum in Chicago displays a fossil of aT-rex. Below is an alligator. • The word “petrified” means “turning into stone.”

  13. 1. Sediment An animal is buried by sediment 3. Movement Movement of tectonic plates pushes the fossil closer to the surface. 4. Erosion Erosion from rain, rivers, and wind wears expose the fossil 2. Layers layers accumulate above the animal’s remains. Water seeps into tiny air spaces depositing minerals turning bone into rock. Petrified Fossils

  14. MOLD FOSSIL This mold, or imprint, is of an extinct mollusk called an ammonite. CAST FOSSILThis ammonite cast was discovered in the United Kingdom. MOLDS AND CASTS • A mold forms when hard parts of an organism are buried in sediment, but dissolve over time, leaving behind a hollow area with the organism’s shape. • A cast forms as the result of a mold. • Water with dissolved minerals and sediment fills the mold’s empty spaces and hardens. • A cast is the opposite of its mold.

  15. cast fossil or mold fossil? 1 2 3 4

  16. CARBON FILMS • When an organism dies and is buried in sediment, the materials that make up the organism break down. • Eventually, only carbon remains. • The thin layer of carbon left behind can show an organism’s delicate parts, like leaves on a plant.

  17. TRACE FOSSILS • Trace fossils show the activities of organisms.

  18. PRESERVED REMAINS Tar Ice Some organisms get preserved in or close to their original states. http://www.news.com.au/travel/travel-updates/pickled-mammoth-shows-off-timeless-style-in-hong-kong-display/story-e6frfq80-1226324359962 Amber http://www.ucmp.berkeley.edu/quaternary/labrea1.gif https://www.youtube.com/watch?v=XQAaWSf3vZw https://www.youtube.com/watch?v=WA3AiNup7fY http://www.history.com/topics/us-states/california/videos/rancho-la-brea-tar-pits

  19. Maybe you will find a fossil? • http://www.huffingtonpost.com/2015/04/08/4-year-old-dinosaur-bones-texas_n_7022842.html AND NOW AN ACTIVITY FOR YOU!

  20. Spread the cards on the table. • The cards represent rock layers. • The letters represent fossils. • Find the card with TC on it. • This is the oldest layer of rock. • Figure out the order of the rest of the layers.

  21. Answer the following questions with your group 1. Which layer is the most recent layer of rock? 2. Which fossil is oldest- X or M? 3. Which fossil is the oldest- B or N? 4. Find a fossil that went extinct? 5. Which fossil lived the longest amount of time? 6. What do we call this idea that we can date fossils based on the layer of rock they are found?

  22. Activity 2 • Work in the same group as yesterday • Place your cards on the table • Each card is a layer of earth • The oldest layer is “M” (ignore the rest of the letters) • Figure out the order of the rest of the layers.

  23. Use your rock layers to answer the following questions. 7. Write the sequence of letters from the youngest layer to the oldest layer 8. Name the fossils found in multiple layers. 9. Name the fossils found in only one layer. 10. What can be said about fossils found in only one layer and fossils found in more than one? 11. What could be said about the environment from these time periods? 12. Which is older- the trilobite or the placoderm?

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