Evolution of Life on Earth using the Geologic Time Scale

• I would like you to recall that there are Two main Geologic Eons in the Geologic Time Scale and they are:

A. Precambrian: 4.5 billion years ago to 500 million years ago

B. Phanerozoic: 500 million years ago to present. It is believed that life began fully in the Phanerozoic Eon.

• Eons are further divided into Eras; therefore this study will focus on the Eras in the Phanerozoic Eon. They are:

1. The Cenozoic: This is the most recent Era in the Geologic Time Scale, from about 65 million years ago till present

2. The Mesozoic: From 250 million years ago to 65 million years ago

3. The Paleozoic: From 550 million years ago to 250 million years ago

• NOTE THAT ERAS ARE ALSO SUB-DIVIDED INTO PERIODS WHICH WILL BE DISCUSSED IN DETAILS. Find the interactive resource attached. Think of the times/ number of years attached to each event as your birthdate. Now imagine how each organism you see today has evolved over the geologic years.