Radiation

Question 1

Which statements about geologic time are true? Check all that apply.Scientists developed the geologic time scale as they studied rock layers and index fossils.The fossil record helps scientists describe life only in the seas and other bodies of water.Precambrian time is the most recent time in Earth’s history.Precambrian time makes up 88 percent of Earth’s history.The first birds appeared during the Mesozoic Era.The basic units of the geologic time scale are periods, eras, and centuries.Humans appeared during the Cenozoic era.

Revolt · Accepted Answer

Scientists developed the geologic time scale as they studied rock layers and index fossils.; Precambrian time makes up 88 percent of Earth’s history.; The first birds appeared during the Mesozoic Era.; Humans appeared during the Cenozoic era.

Question 2

Which event happened first in Earth’s evolution on the geologic time scale?

Revolt · Accepted Answer

A ball of dust, ice, and rock was pulled together by gravity.

Question 3

Which events contributed to life evolving on Earth? Check all that apply.Organisms began to photosynthesize.The surface cooled, and water condensed.Volcanoes added carbon dioxide to the atmosphere.Ozone formed and blocked ultraviolet rays from the Sun.Comets crashed into Earth, releasing water.

Revolt · Accepted Answer

Organisms began to photosynthesize.; The surface cooled, and water condensed.; Ozone formed and blocked ultraviolet rays from the Sun.

Radiation Answers

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