Exam 12: Earths Evolution Through Geologic Time

______are the earliest life forms identified on Earth and they date back to nearly 3.5 billion years ago.

Many reptile groups became extinct at the close of the ______.

Western North America is the leading edge of the ______plate.

What was not one of the gases that made up Earth's original atmosphere?

Toward the end of the Mesozoic era, the ______orogeny formed the southern ranges of the Rocky Mountains.

Which of the following was an important factor in determining where the small rocky planets formed as opposed to where the light, gaseous planets formed?

Well preserved remains of many tiny organisms extend the record of life back beyond______ billion years.

The Cenozoic era is often called the "age of______ ."

The modern oceans are a major repository for the greenhouse gas______ , which some organisms utilize to make their shells.