Is Iridium In Rocks A Unidirectional Change

1. The number of species of fossil organisms that has been described is about a. 50,000.

2. In undisturbed strata of sedimentary rocks, a. the oldest rocks lie at the top.

b. the oldest rocks lie at the bottom.

c. the oldest rocks are in the middle.

d. the oldest rocks are distributed among the strata of younger rocks.

e. None of the above

3. Radioactive carbon can be used to date the ages of fossil organisms because a. all organisms contain many carbon compounds.

b. radioactive carbon has a regular rate of decay to nonradioactive carbon.

c. the ratio of radioactive to nonradioactive carbon in living organisms is always the same as that in the atmosphere.

d. the production of new radioactive carbon in the atmosphere just balances the natural radioactive decay of 14C.

e. All of the above

4. An important unidirectional change in Earth during its history was a a. steady increase in volcanic activity.

b. gradual coming together of the continents.

c. steady increase in the oxygen content of the atmosphere.

d. gradual warming of the climate.

e. steady increase in Earth's precipitation.

5. The total of all species of organisms in a given region is known as the region's a. biota.

d. flora and fauna.

e. diversity.

6. The coal beds we now mine for energy are the remains of a. trees that grew in swamps during the Carboniferous period.

b. trees that grew in swamps during the Devonian period.

c. trees that grew in swamps during the Permian period.

d. small plants that grew in swamps during the Carboniferous period.

e. None of the above

7. The cause of the mass extinction at the end of the Ordovician was probably a. the collision of Earth with a large meteorite.

b. massive volcanic eruptions.

c. massive glaciation in Gondwana.

d. the uniting of all continents to form Pangaea.

e. changes in Earth's orbit.

8. The cause of the mass extinction at the end of the Mesozoic era probably was a. continental drift.

b. the collision of Earth with a large meteorite.

c. changes in Earth's orbit.

d. massive glaciation.

e. changes in the salt concentration of the oceans.

9. The times during the history of life when many new evolutionary lineages appeared were the a. Precambrian, Cambrian, and Triassic.

b. Precambrian, Cambrian, and Tertiary.

c. Cambrian, Paleozoic, and Triassic.

d. Cambrian, Triassic, and Devonian.

e. Paleozoic, Triassic, and Tertiary.

10. Many scientists believe that the collision of Earth with a large meteorite was a major contributor to the mass extinction at the end of the Cretaceous period because a. there is an iridium-rich layer at the boundary of rocks between the Cretaceous and Cenozoic.

b. a crater that may be the site of the collision has been found off the Yucat√°n Peninsula.

c. the mass extinction at the end of the Cretaceous may have been very sudden.

d. many planktonic organisms and bottom-dwelling invertebrates became extinct.

e. All of the above

11. We know that organisms can evolve rapidly because a. the fossil record reveals periods of rapid evolutionary change.

b. theoretical models of evolutionary change show that rapid change can be produced by natural selection.

c. rapid evolutionary changes have been produced under artificial selection.

d. rapid evolutionary changes have been measured in natural populations of organisms during the past century.

e. All of the above

12. At which of the following times was there no mass extinction?

a. The end of the Cretaceous period b. The end of the Devonian period c. The end of the Permian period d. The end of the Triassic period e. The end of the Silurian period

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Responses

  • Lisa
    Is iridium in rocks a unidirectional change?
    8 years ago
  • Aman
    Which of the following changes in earth's history is a unidirectional change?
    8 years ago
  • ROGER
    Why radioactive change is always unidirectional?
    2 years ago

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