Miller and Urey Experiment
Stanley L. Muller and Harold C. Urey conducted an experiment to explain the origin of life on earth. They believed that the early earth’s atmosphere was capable of producing amino acids from inorganic substances. The two biologists used water, methane, ammonia, and hydrogen which they believed were present in the early earth’s atmosphere. The chemicals were sealed inside sterile glass tubes and flasks connected together in a loop and circulated inside the apparatus.
One flask is half-filled with water and the other flask contains a pair of electrodes. The water vapour was heated and the vapour released was added to the chemical mixture. The released gases circulated around the apparatus imitating the earth’s atmosphere. The water in the flask represents the water on the earth’s surface and the water vapour is just like the water evaporating from lakes, and seas. The electrodes were used to spark the fire to imitate lightning and storm through water vapour.
The vapours were cooled and the water condensed. This condensed water trickles back in the first water flask in a continuous cycle. After a week, Miller and Urey analyzed the cooled water and observed that 10-15% of the carbon was in the form of organic compounds. 2% of carbon had formed 13 amino acids. Still, the Miller and Urey experiments were criticised by their fellow scientists.
Also read: Origin Of Life
Criticism of the Miller Urey Experiment
The experiment failed to explain how proteins were responsible for the formation of amino acids. A few scientists have contradicted that the gases used by Miller and Urey are not as abundant as shown in the experiment. They were of the notion that the gases released by the volcanic eruptions such as oxygen, nitrogen, and carbon dioxide make up the atmosphere. Therefore, the results are not reliable.
Oparin and Haldane
In the early 20th century, Oparin and Haldane suggested that if the atmosphere of the primitive earth was reducing and if it had sufficient supply of energy such as ultraviolet radiations and lightning, organic compounds would be synthesised at a wide range.
Oparin believed that the organic compounds would have undergone a series of reactions to form complex molecules. He suggested that the molecules formed coacervates in the aqueous environment.
Haldane proposed that the atmosphere of the primordial sea was devoid of oxygen, and was a composed of ammonia, carbon dioxide, and ultraviolet light. This gave rise to a host of organic compounds. The sea contained large amounts of organic monomers and polymers, and the sea was called a ‘hot dilute soup’. He conceived that the polymers and monomers acquired lipid membranes. The molecules further developed and gave rise to the first living organism. ‘Prebiotic soup’ was the term coined by Haldane.
Also read: Evolution of Life on Earth
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