Question

Why are viruses not included in the three-domain classification system?

Answer 1

Viruses:

1. Viruses are not regarded as living things because they fall short of a few key requirements for life.
2. For instance, viruses and prions do not contain cells and do not have an energy metabolism system.
3. A virus is a submicroscopic infectious agent that can only reproduce inside of another living thing.
4. It spreads to all living things, including plants, animals, and bacteria.
5. They are alive inside the bodies of other species even when they are dead outside the environment.
6. Because they lack any of the characteristics of the three realms of life, viruses are not included in those categories.
7. They have a capsid-encased DNA or RNA strand.
8. They lack any cell organelles, hence they are unable to carry out any type of metabolic activity.