17-1 The Fossil Record

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• 17-1 The Fossil Record
• The fossil record reveals these facts
• fossils occur in a particular order
• certain fossils appear in older rocks
• . . .and other fossils appear in more recent
  rocks.

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In other words, the fossil record shows that life
on Earth has changed over time. In fact, more
than 99 of all species that have ever lived on
Earth have become extinct, which means species
die out.
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Relative dating, the age of a fossil is
determined by comparing its palcement with that
of fossils in other layers of rock.
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Radioactive dating is the use of half-lives to
determine the age of a sample.
Half-lives is the length of time required for
half of the radioactive atoms in a sample to
decay.
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Beta decay
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electron capture