Unit Test — Unit test Answers

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Study the timeline.

Humans have only recently existed on Earth.

Organisms originally lived only on land.

Life on Earth started before water formed on Earth.

Multicellular life evolved before complex single-celled life.

Why is radioactive dating important when approximating the age of Earth?

Scientists can identify different life forms using index fossil records.

Scientists can examine how temperature changes within Earth’s interior.

Scientists can determine the order of when rocks formed on Earth.

Scientists can analyze changes in chemical concentration of atmospheric gases.

Which statement describes what happens to elements during radioactive decay?

They release energy.

They gain new particles.

They lose energy at a varying rate.

They have a consistent number of particles.

Which phrase describes the element carbon-14?

decays at an unknown rate

found in an organism’s remains

forms from the breakdown of nitrogen-14

is measured to determine the age of sedimentary rocks

Study the graph about oxygen content of Earth’s atmosphere.Which describes oxygen content as Earth evolved over time?

Oxygen levels sharply declined about 400 million years ago.

Oxygen levels stay above 15 percent starting 200 million years ago

Oxygen levels remain below 5 percent starting 1000 million years ago.

Oxygen levels raise significantly between 1000 and 700 million years ago.

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