Fossils

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  • This dragonfly was petrified by calcium carbonate (calcite) that covered its surface. This type of example, called Calcareous sinter, is often occurred in hot springs or limestone region (limestone caves). As dragonflies are poikilotherm, they cannot move when their body temperature is low. So they raise body temperature by exposing themselves in the sunlight or by moving flight muscles. This dragonfly probably wandered off into a dark cave and became unable to move, and was soon covered with limy substance to be a stone like this.
  • Fossils

    1. 1. Fossilsevidence for evolution
    2. 2. Three main types of fossils:Actual remains Imprints Petrification
    3. 3. Three main types of fossils:Actual remains•bones•teeth•shells•amber•frozen in ice
    4. 4. Three main types of fossils:Actual remains•bones•teeth•shells•amber•frozen in ice
    5. 5. Three main types of fossils:Actual remains Imprints•bones molds or casts•teeth in mud, sand,•shells etc. that turn•amber to stone•frozen in ice
    6. 6. Three main types of fossils: Imprints molds or casts in mud, sand, etc. that turn to stone
    7. 7. Simulation of how imprint fossils are formedhttp://www.classzone.com/books/earth_science/terc/content/visualizations/es2901/es2901page01.cfm
    8. 8. Three main types of fossils:Actual remains Imprints•bones molds or casts•teeth in mud, sand,•shells Petrification etc. that turn•amber minerals to stone•frozen in ice replace the cellular material and harden to stone
    9. 9. This dragonfly was petrified by calcium carbonate (calcite) that covered itssurface. This type of petrification can occur in hot springs limestone caves.
    10. 10. Most fossils are preserved in sedimentary rock.Sedimentary rock usually forms when small particles of sand, silt, clay,or lime muds settle to the bottom of a body of water.As sediments build up, they bury dead organisms that have sunk to thebottom.
    11. 11. end of part 1
    12. 12. Most fossils are dated using a combination ofrelative dating and radiometric techniques.
    13. 13. Relative Dating Lower layers of sedimentary rock, and fossils they contain, are generally older than upper layers. Relative dating places rock layers and their fossils into a temporal sequence.
    14. 14. To help establish the relative ages of rock layers and their fossils,scientists use index fossils. Index fossils are distinctive fossils used toestablish and compare the relative ages of rock layers and the fossilsthey contain.If the same index fossil is found in two widely separated rock layers, therock layers are probably similar in age.
    15. 15. Radiometric Dating Relative dating is important, but provides no information about a fossil’s absolute age in years. One way to date rocks and fossils is radiometric dating. Radiometric dating relies on radioactive isotopes, which decay, or break down, into nonradioactive isotopes at a steady rate. Radiometric dating compares the amount of radioactive to nonreactive isotopes in a sample to determine its age.
    16. 16. We detect these particles and the energy thatcomes with it as radiation
    17. 17. The process of losing particles is called decay.  decay causes the atom to become something else: potassium-40 argon-40 carbon-14 nitrogen-14 uranium-238 lead-206
    18. 18. the original material is called the parent isotopethe material it becomesis called the daughterproduct
    19. 19. Half-life : the length of time required for 50% of theparent material to decay into the daughter product. What’s the half-life of What’s the half-life of strontium-90? strontium-90?
    20. 20. Half-life : the length of time required for 50% of theparent material to decay into the daughter product. What’s the half-life of What’s the half-life of strontium-90? strontium-90? Answer: 25 years Answer: 25 years
    21. 21. Rates of decay are specific, constant, andmeasureable. •Which is why they can be used for dating fossils once a standard has been developed.
    22. 22. If a geochemical laboratory determines that the volcanic ashin a sample of siltstone has a ratio of U-235 to Pb of 2:3, howold is the ash?
    23. 23. 2+3 = 5 and 2/5 x 100 = 40% ANSWER: about 900 million years old
    24. 24. the end

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