Question

Why are viruses not classified into one of the three domains?

Answer 1

A biological classification developed by Carl Woose in the year 1990, in which various life forms are divided into three parts: archaea, bacteria and eukaryote, is known as a three domain system. It splits the archaea from bacteria, which makes it different from the other classification.

Complete answer:
A biological classification developed by Carl Woose in the year 1990, in which various life forms are divided into three parts: archaea, bacteria and eukaryote, is known as a three domain system. The main difference from other classification is that it separates archaea from bacteria. On the basis of the difference in 16S rRNA, it separates the archaea, bacteria and eukaryotes. And later on, each domain was divided into several other kingdoms.

Virus is a submicroscopic, infectious agent which has the ability to replicate itself only inside the other living organism. From animals to plants to microorganisms, it infects all life forms. More than 9000 species of viruses have been discovered so far. They are the most numerous biological entities and they are present in every ecosystem. Earlier it was known as contagium vivum fluidum which means soluble living germ. They are dead outside the environment and live inside the body of other organisms.

Viruses are not classified into the three domains of life because they don't possess any of their traits. Not even one gene is shared by all the viruses. They are considered as non living cells. They possess a DNA or RNA strand covered with a capsid. They can not perform any kind of metabolic activity because they don't have any cell organelles. Hence they are not classified in any of the three domains of life.

Note:
Virus is a submicroscopic, infectious agent which has the ability to replicate itself only inside the other living organism. Viruses are not classified into the three domains of life because they don't possess any of their traits. They are considered as non living cells.