Are Viruses Distinct from Living Organisms?
Viruses are microscopic intracellular parasites. This describes and differentiates viruses from all other groups of living organisms.Even a broader definition of microbiology encompassing prokaryotic organisms and microscopic eukaryotic such as algae, protazoa and fungi in most cases will suffice. Some groups of prokaryotic organisms have specialized intracellular paracitic life cycles and challenge the above definition. The Rickettsiae and Chlamydiae which obligate parasitic bacteria that have evolved to be cell-associated that can exist outside the cells of their hosts for a short period of time before losing viability. Therefore, we have to ask further what constitutes a virus.
Virus particles are produced from an assembly of components,whereas, others grow from the increase of the integrated sum of their components and reproduce by division.
The partices ,called virions do not grow or undergo division. Viruses do not have the information that codes apperatus necessary for the generation of metabolic energy or for protien systhesis which is called ribosomes.
There is no known virus that has the genetic potencial to generate the energy necessary to drive all biological processes. They are absolutely dependent on the host cell for this function.