Day 36
On your 4.5-meter geological timeline, about
where would trilobites first appear? (You may
use your books and notes to answer this.)
Trilobites appeared toward the beginning
of the Cambrian period, which was at the
start of the Paleozoic era. They would be
near the heavy line between the Paleozoic
era and Precambrian time, on the today
side of the line.
Daily Warm-Up Exercises
1
Relative Scale and
Magnification
Exercise 7.1
2
CaSE Book Student
Resources Book, page 51
3
CaSE Book Student Resource Book, pp.
52-53 and Lab Notebook, p. 51
4
Identify Index Fossils
(Part 1, steps 2-9)
Investigation 7
Fossils and Time
5
Fossils
Fossils are the remains or traces of
organisms that have been preserved in
Earth's crust.
They provide geologists with important
evidence about prehistoric environments.
Some fossils also provide evidence of the
age of rock layers.
These fossils are called index fossils.
6
Index Fossils
Not all fossils are Index Fossils.
Index fossils are fossils of organisms that
lived for only a short time, but in many
places around the world.
Which would be a better index fossil: a fern
that lived for 300 million years or a trilobite that
lived in many areas for a few million years?
The trilobite, because it lived for a short
time over much of the Earth.
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Index Fossil Key
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Index Fossil Key
The Index Fossil Key shows the period in
which the organism lived and whether it lived
early, middle, or late in the period.
Early means toward the beginning of the
period. Late means toward the end.
For example, early Permian rocks are older
than late Permian rocks.
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Index Fossil Identification
Write the
Write the
name of the age of
Index fossil the Index
fossil
Remember: Not all fossils
are index fossils
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Bryce & Zion Canyon Fossils
Identify the index fossils and their ages.
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