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Question

Assertion: Oparin and Haldane proposed that the first form of life could have come from pre-existing non-living organic molecules.
Reason: The condition of early Earth were high temperature, volcanic eruptions, reducing atmosphere with methane, ammonia, and oxygen.

A
Both the assertion and reason are true and reason is the correct explanation of the assertion
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B
Both assertion and reason are true but reason is not the correct explanation of the assertion
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C
Assertion is true but the reason is false
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D
Both assertion and reason are false
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Solution

The correct option is C Assertion is true but the reason is false
Oparin and Haldane proposed the modern theory of origin of life. According to them, the first form of life could have come from pre-existing non-living organic molecules (RNA, protein etc.). Hence assertion is a true statement.

In 1953 Miller and Urey performed an experiment popularly known as Miller’s experiment and proved the modern theory of life by Oparin and Haldane.


Figure : Miller and Urey's experimental setup

With the help of glass apparatus, they created early Earth conditions in the lab, where boiling water represented the ocean and gas chamber represented an early atmosphere, in which methane, ammonia, and hydrogen were present in the ratio 2:2:1. Electric spark created with the help of a spark chamber and two electrodes maintained a temperature of 800°C in this apparatus, which represented volcanic eruptions, thunderstorm and lightning conditions of the early Earth.

The spark chamber was connected to another flask with arrangement for boiling water, to continue evaporation. The other end of the spark chamber was connected to a trap by a tube that passed through a condenser. The condenser was required for condensation and collection of aqueous solution equivalent to rain. The trap was connected with the flask, for boiling water (arrangement for circulation of water).

They ran this experiment continuously for seven days. In this duration, the colour of the water inside the apparatus changed to brown-black. When this sample was analysed, it confirmed the presence of simple amino acids (alanine, glycine and aspartic acid) and aldehydes. Other substances, such as urea, hydrogen cyanide, lactic acid and acetic acid were also present in the water sample.

On the basis of this, they proposed that the first form of life on Earth, could have come from pre-existing non-living organic molecules the same way as occurred in this experiment.

Based on the evidences, early Earth conditions were high temperature, volcanic eruptions, reducing atmosphere with methane, ammonia, hydrogen and many other gases. As oxygen was absent and reducing gases like hydrogen was present, early atmosphere is considered as reducing atmosphere. Thus the reason is a false statement.

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