Question

Life cannot originate from inorganic materials at present because .......

• A. High degree of environmental pollution.
• B. A very high amount of oxygen in the atmosphere.
• C. Very high atmosphere temperature.
• D. Absence of raw materials.

Answer 1

The correct option is B A very high amount of oxygen in the atmosphere.

The primitive atmosphere of earth was reducing atmosphere with little or no oxygen but was rich in water vapour, carbon monoxide, carbon dioxide, nitrogen and hydrogen. UV light, high temperature and lightening served as sources of energy for chemical reactions between primitive gases to form simple inorganic elements such as water, ammonia, methane and cyanides. This makes option D incorrect as the primitive gases, the raw materials, are present in today’s atmosphere also. These simple elements were washed from atmosphere to ocean through rain wherein polymerization and condensation reactions formed simple organic compounds such as sugars, amino acids, fatty acids, glycerol and nucleotides. The complex organic molecules were formed in oceans as facilitated by presence of high temperature and presence of monomers. This makes option C incorrect as high temperature favours origin of life from simple inorganic elements. Absence of oxygen prevented spoilage of organic molecules as well as facilitated their combination reactions to produce more complex organic compounds. Appearance of photoautotrophs that use light as source of energy and carbon dioxide as chief carbon source, added oxygen to atmosphere. Owing to presence of oxygen, the organic and inorganic compounds are oxidized as soon as they are formed. Origin of life requires accumulation of these compounds followed by their organization into a living cell. This makes option B correct. Environmental pollution does not play any role in origin of life. Correct answer is B.