2
Question
Life can not originate today because
Life can not originate today because
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Solution
The correct option is D Today's atmosphere is oxidizing.
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 above mentioned gases to form simple organic compounds such as sugars, amino acids, fatty acids, glycerols and nucleotides. This makes option A incorrect as the primitive gases are present in today’s atmosphere also. These simple organic compounds were washed from atmosphere to ocean through rain. The complex organic molecules were formed in oceans as facilitated by presence of high temperature and presence of monomers. 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. This makes option C incorrect as today’s atmosphere is oxidizing. These photoautotrophs use water as electron donor during photophosphorylation that results in production of oxygen. Owing to presence of oxygen, the organic compounds are oxidized as soon as they are formed. Origin of life requires accumulation of these organic compounds followed by their organization into a living cell. This makes option D correct. In presence of favourable earth conditions, new life forms can be originated; option B is incorrect. Therefore, the correct answer is option D.
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 above mentioned gases to form simple organic compounds such as sugars, amino acids, fatty acids, glycerols and nucleotides. This makes option A incorrect as the primitive gases are present in today’s atmosphere also.
These simple organic compounds were washed from atmosphere to ocean through rain. The complex organic molecules were formed in oceans as facilitated by presence of high temperature and presence of monomers. 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. This makes option C incorrect as today’s atmosphere is oxidizing.
These photoautotrophs use water as electron donor during photophosphorylation that results in production of oxygen. Owing to presence of oxygen, the organic compounds are oxidized as soon as they are formed. Origin of life requires accumulation of these organic compounds followed by their organization into a living cell. This makes option D correct.
In presence of favourable earth conditions, new life forms can be originated; option B is incorrect.
Therefore, the correct answer is option D.
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