Page 106 - Science Course 3 (Book 1)

Mo3-L1a: How are Fossils Formed? Mo3-L1b: What is the Evidence for
Evolution?

Determining a Fossil’s Age SUMMARY

Instead of dating fossils directly, scientists date the How are Fossils Formed?
rocks the fossils are embedded inside.
Fossils can consist of the hard parts or soft
In relative-age dating, scientists determine the parts of organisms. Fossils can be an
relative order in which rock layers were deposited. impression of an organism or consist of
original tissues.
Relative-age dating helps scientists determine the
relative order in which species have appeared on Scientists determine the age of a fossil
Earth over time. through relative age dating or absolute-age
dating.

Volcanic-ash bed
325 million years old
Age of boundary:
about 355 million years

Basalt lava flow
385 million years old

Mo3-L1b What is the Evidence for Evolution?

Key Concept KEY CONCEPTS:

How are Fossils Formed? 1. How are fossils evidence of biological evolution?
How does relative-age dating help scientist learn
about fossils?
Vocabulary A-Z

Let us learn some vocabulary

Geological Time Scale
a chart that divides Earth’s history into different time
units based on changes in the rocks and fossils.

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