Chapter 10, Section 5 Earth’s Geologic Timescale I will describe how scientists use fossil and rock evidence to create Earth’s Geological timescale.

Agree Disagree 1._______ ________ 2._______ ________ 3._______ ________ 5._______ ________ 4._______ ________ Earth’s history is divided based on extinctions of different species. A majority of the organisms that have existed on Earth are extinct today. The dinosaurs were the first organisms to walk on land. The time we are currently living in is called the Mesozoic Era Climate change is believed to be the cause of many mass extinctions.

Geologic Time Scale: Timeline showing divisions of Earth’s history

I. Paleozoic Era A. Explosion of Life – large amounts of new organisms appear in the oceans

B. Vertebrates (animals with a backbone) appear C. Amphibian – animal that lives both on land and in water

D. Ends with Pangaea forming and a mass extinction of major species.

II. Mesozoic Era A. Age of Reptiles, dinosaurs were the dominant species

B. Ends in mass extinction = the climate was changed by an asteroid hitting Earth and volcanic eruptions

III. Cenozoic Era A. Mammals evolve and become the dominant life forms on Earth B. Earth cooled during a series of ice-ages

Agree Disagree 1._______ ________ 2._______ ________ 3._______ ________ 5._______ ________ 4._______ ________ Earth’s history is divided based on extinctions of different species. A majority of the organisms that have existed on Earth are extinct today. The dinosaurs were the first organisms to walk on land. The time we are currently living in is called the Mesozoic Era Climate change is believed to be the cause of many mass extinctions.