Quiz 20: Lifes Origin and Early Evolution

Biology

Yes, life can exist with the atmosphere containing huge amounts of carbondioxide even though there is low nitrogen and oxygen. Anaerobic forms can exist in the Mars atmosphere. These can be simple living forms that could currently exist. For example Nanobes which are like proto-cells found in the hot rocks beneath the Earth's surface. They have DNA and other organic compounds enclosed with a membrane and can grow. Hence, life can take in almost any environment that has sources of carbon and energy.

Oxygen is the main atmospheric gas for the living organisms on the earth. The abundance of oxygen in the atmosphere would have prevented the spontaneous abiotic assembly of organic compounds on the early earth. a. Oxygen: Oxygen is available in free form at a very little amount during the early earth but later it became the abundant gas, which is used for the living organisms. The oxygen prevented the spontaneous a biotic assembly of organic compounds on the early earth. Hence, the correct option is (c) oxygen. b. Hydrogen: Hydrogen gas is the most abundant gas in the earth's atmosphere, but is not used for the biotic organisms to live. Hence, the option (a) is incorrect. c. Methane: Methane is the gas which is formed during the early earth period when living organisms are not formed. It is one of the earth's atmospheres between 4.5 to 4.6 billion years ago. Hence, the option ( b) is incorrect. d. Nitrogen: Nitrogen is not used for the biotic organisms to grow and it doesn't prevent the abiotic organism's growth. Hence, the option (d) is incorrect.

There are several assumptions and hypothesis that from where the cells originate and the life begins. Cells originate or life arose on tidal flats can be explained from the prevalence of the iron-sulfide cofactors in the living organisms are the evidences. a. On tidal flats: It is one of the hypothesis clay of tidal flats bound and protected the newly forming polymers. Certain clay mineral ions which attract amino acids or nucleotides, and these stick and form bonds. And for further formation of chains which resemble the proteins and nucleic acids in living cells. Hence, the correct option is (b) on tidal flats. b. In outer space: Life is not started from the outer space. Outer space has some atmospheric gases where there is absence of life. Only simple organic compounds are formed in outer space. Hence, the option (a) is incorrect. c. Near deep-sea vents: Life is not formed in the near deep-sea vents. It is a hypothesis. Hence, the option (c) is incorrect. d. In the upper atmosphere: Upper atmosphere contains some atmospheric gases where life is not started from it. Hence, the option (d) is incorrect.

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