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| Experimental Evidence |
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| As the theory of chemical evolution started gaining more support, investigations were initiated by several scientists to establish the conditions under which, the simplest organic compounds were formed in the primitive earth. Two scientists, Stanley Miller and Harold Urey were the first to put to test, the Oparin - Haldane theory, in the year 1953. |
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| Urey and Miller designed a glass apparatus which came to be known as Spark-discharge apparatus. It consisted of a flask, a gas chamber and a condenser connected in series, as shown in the figure. The flask consisted of water, which was boiled thoroughly to produce water vapour. The gas chamber consisted of two tungsten electrodes placed at a distance of 0 to 1 cm and connected to terminals. When the electrodes were connected they produced a high energy spark of about 75,000 volts. |
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| Spark Discharge Apparatus |
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| Prior to the experiment, Urey and Miller evacuated the entire apparatus. Through the inlet, they passed a mixture of ammonia, methane and hydrogen in the ratio of 2:2:1 by volume. Along with the water vapour produced in the flask, these gases were made to enter the spark discharge chamber when the electrodes were switched on. Chemical reactions occurred in the spark discharge chamber and the products formed were cooled by circulating water in the condenser. These products were collected from the trap and subjected to analysis. The experiment was run continuously for about a week. |
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| The analysis conducted on the products obtained in this experiment, revealed that the products contained many simple organic compounds which included amino acids like glycine, alanine and aspartic acid. |
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| This experiment clearly supported the hypothesis that in the ancient earth primitive gases could have reacted with one another to form simple organic molecules, in the presence of high-energy sources. |
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| Similar experiments conducted with more refined techniques by other scientists like Sydney Fox, have clearly demonstrated that most of the amino acids that are found in proteins and nucleotides found in nucleic acids can be synthesized in the laboratory by simulating the conditions of primitive earth. |
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