Chapter 6
The Environment & Change Over Time

Study Guide

Lesson 1- Fossil Evidence of Evolution

Fossils can consist of the hard parts or soft parts of organisms. Fossils can be an impression of an organism or consist of original tissues.

Scientists determine the age of a fossil through relative-age dating or absolute-age dating.

Scientists use fossils as evidence that species have changed over time.

Lesson 2- Theory of Evolution by Natural Selection

Charles Darwin developed his theory of evolution partly by observing organisms in their natural environment.

Natural selection occurs when organisms with certain variations live longer, compete better, and reproduce more often than organisms that do not have the variations.

Adaptations occur when a beneficial variation is eventually inherited by all members of a population.

Lesson 3- Biological Evidence of Evolution

By comparing the anatomy of organisms and looking for homologous or analogous structures, scientists can determine if organisms had a common ancestor.

Some organisms have vestigial structures, suggesting that they descended from a species that used the structure for a purpose.

Scientists can use evidence from developmental and molecular biology to help determine if organisms are related.

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