Page 106 - Science Course 3 (Book 2)

Mo11-L1b: Fossils: What is in the Ancient Environment?

A cast is a fossil copy of an organism made when a Ancient Environments
mold of the organism is f lled with sediment or
mineral deposits. Scientists who study fossils are called paleontolo-
gists.

Paleontologists use the principle of uniformitari-
anism to learn about ancient organisms and the
environments in which they lived.

The fossils begins to The fossil has been
dissolve as waters dissolved away. The
move through spaces in harder rock once
the rock layers surrounding it forms a
mold.

Sediment washes into A cast result Studying fossils helped scientists reconstruct this
the mold and is depos- 450-million-year-old North American seaf oor. Most
ited, or mineral crystals of what would become the United States was
form. covered by a shallow sea during that time.

A trace fossil is the preserved evidence of the activity
of an organism.

Trace fossils include tracks, footprints, and nests
and help scientists learn about characteristics and
behaviors of animals.

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