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Studying Fossils
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Studying Fossils

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  • 1.  
  • 2.
    • Fossils are preserved remains or traces of living things.
    • Most fossils form when living things die and are buried by sediments.
    • The sediments slowly harden into rock and preserve the shape of the organisms.
    • Scientists who study fossils are paleontologists.
  • 3.
    • Fossils are usually found in sedimentary rocks.
    • When an organism dies, its soft parts often decay quickly leaving only the hard parts to fossilize.
    • Ex. Bones, Shells, Teeth, or Seeds
  • 4.
    • Petrified Fossils : fossils in which minerals replace all or part of the organism. Ex: petrified wood
    • When the object is buried by sediment, water rich in minerals seeps into the cells. After the water evaporates, hardened minerals are left behind.
  • 5.
    • Molds and Casts
    • A mold is a hollow area in sediment in the shape of an organism or part of an organism.
    • A cast is a copy of the shape of an organism.
  • 6.
    • Carbon Films : an extremely thin coating of carbon on rock that forms when materials that make up an organism become gases and escape leaving only carbon behind.
    • Trace Fossils provide evidence of the activities of ancient organisms. Ex: footprints, animal trails, or animal burrows.
  • 7.
    • Preserved Remains are formed when an organism is preserved with little or no change.
    • For example when organisms become preserved in tar, amber (tree sap), and freezing.
  • 8.
    • Scientists study fossils to learn what past life forms were like.
    • Paleontologists classify organisms in the order in which they lived.
    • All the information scientists have gathered is called the fossil record .
  • 9.
    • The fossil record provides evidence about the history of life on Earth.
    • The fossil record also shows how different groups of organisms have changed over time.
    • It also provides evidence to support the theory of evolution.
  • 10.
    • A scientific theory is a well-tested concept that explains a wide range of observations.
    • The fossil record shows that millions of types of organisms have evolved.
    • However, many others became extinct.
  • 11.  
  • 12.  
  • 13.
    • The relative age of a rock is its age compared to other rocks. Use words like: “older or younger”
    • The absolute age of a rock is the number of years since the rock was formed.
    • Ex: 358-360 mya
  • 14.
    • What does a rock want to be when it grows up?
    • A Rock Star!!
  • 15.
    • It can be difficult to determine a rocks absolute age. So… scientists use the law of superposition .
    • According to the law of superposition , in horizontal sedimentary rock layers the oldest layer is at the bottom. Each higher layer is younger than the layers below it.
  • 16.
    • How do rocks wash their clothes?
    • The Rock Cycle!!
  • 17.
    • Clues From Igneous Rock
    • Lava that cools at the surface is called an extrusion. Rock below an extrusion is always older.
    • Magma that cools beneath the surface is called an intrusion. An intrusion is always younger than the rock layers around an beneath it.
  • 18.
    • Faults (a break in the rock) are always younger than the rock it cuts through!
    • Unconformities : An unconformity is a gap in the geological record that can occur when erosion wears away rock layers and other rock layers form on top of the eroded surface.
  • 19.
    • Scientists use index fossils to match rock layers.
    • An index fossil must be widely distributed and represent a type of organism that existed only briefly.
    • They are useful because they tell the relative ages of the rock layers they are found in.
  • 20.
    • One example of an index fossil is a trilobite.
    • Trilobites were a group of hard-shelled animals whose bodies had three distinct parts.
    • They evolved in shallow seas more than 500 million years ago.