7.5.3 and 7.5.5 Timeline of the World
Since the formation of the Earth 4.6 billion years ago, much has happened. The fossil record is quite extensive, especially since the Cambrian explosion, showing a great diversity of life and adaptations over time. Explore the following websites and practice your scientific notation skills in writing out the years.

Overview of the Time Periods:
http://science.nationalgeographic.com/science/prehistoric-world/prehistoric-time-line/

More specific details since the Cambrian Explosion:
http://www.ucmp.berkeley.edu/cambrian/camb.html

Fossils from Pre-Cambrian through Tertiary Age:
http://www.fossilmuseum.net/Paleobiology/Precambrian-Fossils.htm

When Trilobites Ruled the World
http://www.nytimes.com/2014/03/04/science/when-trilobites-ruled-the-world.html