Question

Why are viruses called as the boundary of nonliving and living thing?

Answer 1

Viruses are obligate intracellular parasites which can reproduce only by invading and taking over other cell as they lack the cellular machinery for self reproduction. A virus has a very simple composition. It has a protein sheath inside which there is a strand of DNA or RNA. A virus shows some properties akin to living organisms. However, unlike other organisms, they show some properties that are akin to non-living things.
That is why viruses are called the boundary of nonliving and living thing.