Lesson Summary

There are several causes for extinction including: loss of habitat, climate change, disease and natural disasters.

• Extinction results in a loss of biodiversity, which can have negative consequences for all life.

• The Earth has undergone periods of massive extinctions.

• During the Cretaceous-Tertiary period the dinosaurs became extinct. There are several hypotheses about what caused these extinctions. The leading hypothesis is that the K-T extinctions were caused by an asteroid striking the Earth.

• The Pleistocene extinction happened at the end of the Ice Age and resulted in massive extinctions in N. America.

• There are several reasons to preserve species and maintain biodiversity. These reasons include maintaining valuable genetic material and mutually beneficial relationships.