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The History of Life on Earth
Looking at fossils
10
Science
7th Grade
01/21/2010

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Term
Fossil
Definition
the trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock.
Term
Ways a fossil can form
Definition
in rocks, in amber, when frozen, in asphalt, and in petrification
Term
Petrification
Definition
the filling or replacement of an organism's tissues with minerals that have different chemical compositions than the origional tissues did
Term
Trace Fossil
Definition
a fossilized structure, such as a footprint or a coprolite that formed in sedimentary rock by animal activity on or within soft sediment
Term
Molds and casts
Definition
the impression left in sediment or in rock where a plant or animal was buried
Term
Fossil Record
Definition
the history of life in the geologic past as indicated by the traces or the remains of living things.
Term
What are ways scientists organize fossils and how?
Definition
They sort fossils by age. They use absolute dating methods (radiometric dating) or Relative dating methods(superposition)
Term
Index Fossils
Definition
organisms that lived during a relatively short, well-defined geologic time span. Used to date rock layers in which the fossilos are found
Term
Trilobites/ Phacops
Definition
living relatives: horseshoe crabs, spiders, scorpions. Lived 400 milllion years ago
Term
Ammonites/ Tropites
Definition
Marine mollusks similar to the modern squid. lived 230 million to 208 million years ago in ancient oceans
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