A virus is a unique microscopic agent that does not fit neatly into the biological package we call a cell. A cell has:

1. Defined cellular structure with organelles


2. Metabolic infrastructure and function – The ability to convert consumed non-living materials into biological energy and cellular components


3. Homeostatic controls – The ability to regulate the internal environment


4. Reproductive capacity – The ability to produce offspring


5. Responsiveness – The ability to respond to external stimuli and conditions


6. Capacity for growth


7. Capacity for adaptation – The ability to alter form, function, or both over time in response to environmental challenges

A virus is structurally and fu...