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FOSSILS- Evidence from Once-living Organisms

FOSSILS- Evidence from Once-living Organisms. Fossils found in SEDIMENTARY ROCKS. The lower the sediment layer is, the older the fossils of the layer will be.- Law of Superposition As time elapses, more and more sediment layers form to create the layers of sedimentary rocks.

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FOSSILS- Evidence from Once-living Organisms

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  1. FOSSILS- Evidence from Once-living Organisms

  2. Fossils found in SEDIMENTARY ROCKS • The lower the sediment layer is, the older the fossils of the layer will be.- Law of Superposition • As time elapses, more and more sediment layers form to create the layers of sedimentary rocks.

  3. Examples of Sedimentary Rocks

  4. Different Rock Layers of the Earth

  5. Relative dating places rocks in their proper sequence of formation, e.g. which formed first, second etc. Although relative dating cannot give us numeric dates for events that took place, it does provide useful information on what event followed or preceded another event. Relative dating is still very valuable to scientists and still widely used. The discovery of radioactive dating has supplemented relative dating techniques. Oldest? Youngest? Can you put the events in order?

  6. Relative Dating combined with Radioactive Dating

  7. Absolute (Radioactive) Dating of Fossils using the half- life of elements • Half Lives for Radioactive Elements Half-Life of an element is the TIME it takes for HALF of the atoms present to RADIOACTIVELY decay into a stable element.

  8. Types of Radioactive Decay -100x more penetrating than alpha -Neutron changes to one proton, one electron -Electron is emitted from nucleus -2 protons, 2 neutrons -Helium atom -Emitted from the nucleus -no charge or mass -results in only lost energy -Emitted in Photons -most dangerous form

  9. 1/2 C-14 1/4 C-14 1/8 C-14 12.5% C-14 25% C-14 87.5% N-14 100% C-14 50% C-14 50% N-14 75% N-14 5730 years 5730 years 5730 years C-14 Decay PARENT = C-14 DAUGHTER = N-14

  10. Molds • Are “trace fossils” • Are not the organisms themselves, but is evidence that the organism has been there • Depressions in a surface Smurf Mold

  11. Examples of Molds Lobster Fish Trilobite

  12. Casts • Three-dimensional trace of organism • Protrudes out of surface of rock

  13. Examples of Casts Insect Trilobite Eurobrontes (dinosaur footprints)

  14. Imprints • Different from molds—are not indented or depressed into its surface • Different from casts—do not protrude from surface • Thin layer of carbon which forms from where the organism was

  15. Examples of Imprints Fish Leaf

  16. Body Parts • Actual parts of an organism left behind from the past • Example: bones, organisms preserved in amber or ice

  17. Examples of Body Parts A baby mammoth has been uncovered in the permafrost of north-west Siberia. Approx. 9,000 years old. Skull of horned and hornless deer From the Dominican Republic, Miocene epoch (23.8 to 5.3 mya) The 67-million-year-old Tyrannosaurus rex skeleton known as Sue stands on display at Union Station in WashD.C.

  18. Gradualism- pg439

  19. Punctuated Equilibrium-pg439

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