Question

The earth is thought to have formed 4.6 billion years ago. All of the following items describe what conditions may have existed on the early Earth except

• A. An anaerobic atmosphere containing gases such as carbon dioxide and nitrogen
• B. An atmosphere with extremely hot temperatures
• C. Photosynthetic blue-green prokaryotes populating the oceans
• D. A terrestrial environment with frequent volcanic eruptions
• E. Oceans containing a mixture of inorganic compounds such as ammonia

Answer 1

Answer: (C)

A. The composition of early earth atmosphere was carbon dioxide, nitrogen gas, water vapour and hydrogen gas i.e. anaerobic conditions were there as no oxygen was present.

B. It is estimated that the earth has been formed from the left over dust and gases of the sun. It was in the form of a solidified, red-hot cloud containing free atoms and having approximate temperature of 5000-6000° C.

C. The first organisms to appear on earth were chemoheterotrophs i.e. they required chemical organic compounds for the production of energy.

D. Primitive atmosphere of earth was reducing containing methane, ammonia, hydrogen and water vapour. Oceans consists of inorganic molecules like ammonia, methane, hydrogen cyanide, nitrides, carbides and various gases.

E. Early earth was having no atmosphere. The earth's surface was in molten state which after cooling resulted in huge emission of carbon dioxide, water vapours, methane and ammonia from the belching volcanoes.

Hence statement C is incorrect.

So, the correct answer is 'Photosynthetic blue-green prokaryotes populating the oceans'.