Question

First life consisted of
A. Protovirus
B. Provirus
C. Bacteria
D. Virus

Answer 1

Hint: We know that the oldest inhabitants of the earth were microbes. They were the first forms of life. The first life was a free-living virus which is a hypothetical primitive or ancestral virus.

Complete answer:
We know that earth is billions of years old. Information regarding the earliest life form is obtained from studies conducted on rocks and other similar particles. The proto viruses are considered as the earliest form of life on earth. Studies conducted by H.M Temin states that they are the ancestors of viruses that were present on earth and modern viruses have evolved from them. He also stated that they were able to do the process of reverse transcription, in which DNA is formed from RNA. H.M Temin together with another scientist named Baltimore conducted several studies and put forward the theory of reverse transcription. They were awarded the Nobel prize for this contribution. When the viral gene gets incorporated with the genome of the host cell, it is called a provirus. Retroviruses are examples for proviruses as they can infect the host cell, incorporate their genome with the host cell and produce more viral particles by controlling the mechanism of cell division. Archaebacteria are considered as the most primitive forms of bacteria. They were one among the other organisms that were present on earth as early life forms.
Hence, the correct answer is option A.

Note: Viruses have been excluded from the five-kingdom classification of organisms that was put forward by R.H Whittaker. He also excluded viroids and lichens as all of them are acellular in nature.