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12.2: Early Earth

Difficulty Level: At Grade Created by: CK-12
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Lesson 12.2: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. Nucleic acids in living things include DNA and RNA.

_____ 2. Continental crust first appeared on Earth about 2 billion years ago.

_____ 3. The first continents on Earth were very large compared with those today.

_____ 4. Pangaea was the first supercontinent to form on Earth.

_____ 5. Life may have originated on Earth more than once.

_____ 6. The first oxygen on Earth combined with iron to form iron oxide.

_____ 7. Some of the oxygen in Earth’s early atmosphere became ozone.

_____ 8. The first photosynthetic organisms were most like modern E. coli.

_____ 9. There are no longer any prokaryotes living on Earth.

_____ 10. Ediacara fauna evolved toward the end of the Precambrian Era.

Lesson 12.2: Critical Reading

Name___________________ Class______________ Date________

Read this passage based on the text and answer the questions that follow.

Early Continents

Earth’s earliest crust probably consisted of basalt. It may have resembled the current seafloor. However, it formed before there were any oceans. More than 4 billion years ago, continental crust first appeared. The first continents were very small compared with those of today. Continents grew larger when small continents, called microcontinents, collided with each other or with larger continents. Oceanic island arcs also collided with continents to make them grow.

At least five times in Earth’s history all of the continents came together to form a single supercontinent. Each time a supercontinent came together, it later broke apart. Pangaea was the last supercontinent on Earth. The supercontinent before Pangaea is called Rodinia. Rodinia formed about 1.1 billion years ago. It contained about 75 percent of the continental landmass that is present today.

Because early Earth was very hot, convection currents moved rapidly through the mantle. This allowed Earth’s lithospheric plates to move relatively quickly. Therefore, early Earth was a very active place. There were abundant volcanic eruptions and earthquakes.


  1. Describe Earth’s first continents, and explain how they grew.
  2. What are supercontinents? Describe the supercontinent named Rodinia.
  3. Explain why early Earth was very active geologically.

Lesson 12.2: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. The fourth supercontinent to form was
    1. Pangaea.
    2. Rodinia.
    3. Escherichia.
    4. none of the above
  2. The supercontinent in question 1 formed about
    1. 5.0 billion years ago.
    2. 4.5 billion years ago.
    3. 4.0 billion years ago.
    4. 1.1 billion years ago.
  3. Early Earth had
    1. many volcanoes.
    2. high temperatures.
    3. abundant earthquakes.
    4. all of the above
  4. Earth’s earliest life forms
    1. consisted of one cell.
    2. could breathe oxygen.
    3. lacked a cell membrane.
    4. none of the above
  5. The earliest organisms to photosynthesize
    1. first appeared about a billion years ago.
    2. went extinct millions of years ago.
    3. are still common in lakes and seas.
    4. two of the above
  6. Eukaryotes first evolved about
    1. 4.5 billion years ago.
    2. 3.5 billion years ago.
    3. 2.0 billion years ago.
    4. 0.5 billion years ago.
  7. Which of the following types of organisms evolved first?
    1. multicellular organisms
    2. Ediacara fauna
    3. cyanobacteria
    4. eukaryotes

Lesson 12.2: Matching

Name___________________ Class______________ Date________

Match each definition with the correct term.


_____ 1. first organisms to make food by photosynthesis

_____ 2. type of organism that contains a nucleus in its cell(s)

_____ 3. process that added oxygen to Earth’s early atmosphere

_____ 4. gas that protects Earth from harmful radiation

_____ 5. type of organism that lacks a nucleus in its cell(s)

_____ 6. organic compound that stores genetic information

_____ 7. waste product of photosynthesis


a. nucleic acid

b. oxygen

c. eukaryote

d. prokaryote

e. cyanobacteria

f. ozone

g. photosynthesis

Lesson 12.2: Fill in the Blank

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

  1. Earth’s earliest crust was probably made of the rock named __________.
  2. Continents grew on early Earth from collisions of very small continents called __________.
  3. Scientists think that there have been a total of __________ supercontinents in Earth’s history.
  4. Life on Earth probably began in the planet’s __________.
  5. Eukaryote cells have structures called __________ that perform certain functions.
  6. The earliest living cells took their nutrients directly from the __________around them.
  7. There is little evidence of early life on Earth because the organisms did not form __________.

Lesson 12.2: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Outline the history of early life on Earth.

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