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17 Cards in this Set

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Cambrian Explosion
when a great number of different organisms evolved
carbon-14
used by geologists often to date materials that lived up to about 50,000 years
ago
evolution
process when all the different kinds of living things have changed over long
periods of time
fossil
preserved remains or traces of living things
half-life
the time it takes for half of the radioactive atoms to decay in a radioactive
element
intrusion
magma that forces its way into rocks and hardens
paleontologist
a scientist who studies fossils
periods
what the Geologic Time Scale eras are divided into
petrified fossil
when minerals replace all or part of an organism
radioactive dating
scientists use to determine the absolute ages of rocks
reptiles
evolved from amphibians
sedimentary
the level of rock where fossils are most always found
vertebrate
an animal with a backbone
invertebrate
an animal without a backbone
Precambrian Time
when earliest forms of life appeared
Paleozoic Era
when plants and animals first reached land
Mesozoic Era
known as the “Age of the Reptiles”