AP BIOLOGY

Detailed explanation-1: -This eon covers almost 90% of the entire history of Earth. It has been divided into three eras: the Hadean, the Archean and the Proterozoic. Each era is very different. This era begins about 4.6 billion years ago with the formation of Earth from dust and gas orbiting the Sun.

Detailed explanation-2: -The Hadean, Archean, and Proterozoic eons together are called Precambrian time and make up almost 90 percent of Earth’s history.

Detailed explanation-3: -Precambrian (Informal-4.6 billion years ago to 541 million years ago) Precambrian is the informal name for the first 4 billion years, or 88 percent, of Earth’s history.

Detailed explanation-4: -The Precambrian encompasses nearly 90% of the history of the Earth and around a third of the history of the Universe. The Precambrian begins with the formation of the Solar System 4.57 billion years ago (bya) and extends to the beginning of the Cambrian 540 million years ago (Mya, or 0.54 bya).

Detailed explanation-5: -The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth’s geologic time.