Viruses are infectious agents that are not classified as living organisms.

State two life processes that viruses cannot carry out independently (when outside a host cell).

Name one disease in humans that is caused by a virus.

Viroids are plant pathogens discovered in the 20th century. Viroids consist solely of a short, circular strand of RNA and do not possess a protein coat.

Suggest two structural or functional differences between viroids and typical viruses.