
Concept explainers
The Miller-Urey experiment demonstrated that
a. life originated on Earth.
b. organic molecules could have originated in the early atmosphere.
c. the early genetic material on the planet was DNA.
d. the early atmosphere contained large amounts of oxygen.

Introduction:
Stanley Miller and Harold Urey performed an experiment that showed the organic compounds were formed by the stimulation of the early atmosphere of the Earth. Earlier the atmosphere of the Earth was reducing in nature due to the absence of oxygen and the presence of large amounts of hydrogen. Miller and Urey performed their experiments in reducing the environment and check the chemical origin of life under a reducing environment. They found that the reducing environment of the Earth favored more to the formation of organic molecules from the inorganic substances which are present at that time.
Answer to Problem 1U
Correct answer:
The Miller‑Urey experiment showed that the organic molecules could have originated in the early atmosphere. Therefore, option b. is correct.
Explanation of Solution
Reason for the correct statement:
Miller and Urey created an artificial environment in the laboratory which was very similar to the early Earth atmosphere (reducing environment). Their experiment shows that only the organic complex molecules are formed from the inorganic molecules due to the presence of reducing molecules in the environment.
Option b. is given as “organic molecules could have originated in the early atmosphere”.
As “Miller and Urey demonstrated that the organic molecules could have originated in the early atmosphere,” it is the right answer.
Hence, option b. is correct.
Reasons for the incorrect statements:
Option a. is given as “life originated on earth”.
Miller and Urey demonstrated the chemical evolution on the Earth. They could not demonstrate the biological evolution on the Earth. Hence, it is the wrong answer.
Option c. is given as “the early genetic material on the planet was DNA”.
Miller and Urey demonstrated that the organic molecules evolved due to the reducing environment. They could not show that DNA was the earliest genetic material. Hence, it is the wrong answer.
Option d. is given as “the early atmosphere contained large amounts of oxygen”.
The Miller and Urey experiment demonstrated that the earlier nature of the atmosphere of the Earth was reducing in nature due to the absence of oxygen. Hence, it is the wrong answer.
Hence, options a., c. and d. are incorrect.
Conclusion:
Miller and Urey showed that the organic complex molecules were formed due to the presence of reducing molecules in the early atmosphere.
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Chapter 26 Solutions
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