Index Fossils and ancient environments

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Index Fossils and ancient environments
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What are index fossils?

• Index fossils are the remains of species that
  existed on Earth for relatively short periods of
  time
• They were abundant (there were a lot of them)
• They were widespread geographically

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What are index fossils used for?

• Index Fossils are found in different rock layers
• Because index fossils only living during certain
  time periods, we can estimate how old a rock
  layer is

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What are some examples of index fossils?

• Shells
• Mollusks
• Plants
• Trilobites-they inhabited Earths oceans for more
  than 200 million years
• Trilobites lived in the Paleozoic Era
• Trilobites consists of 3 sections (head, middle
  section, and tail)
• Trilobites are one of the most widely used index
  fossils
• We can see the changes of trilobites over time
  (aka evolution)

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Fossils and ancient environments

• Scientists can use fossils to determine what the
  environment of an area was like long ago
• With fossils, we can also determine whether or
  not an area of land was covered with water
• We can determine the types of animals/plants that
  once lived
• Sohow could you explain the presence of a
  fossilized crinoid (animals that lived in shallow
  seas) in rocks found in what is today a desert?