ANATOMY

Detailed explanation-1: -Viroids: the smallest and simplest agents of infectious disease.

Detailed explanation-2: -Viruses are the smallest common pathogen. They are so small in fact that many of them actually infect bacteria. They are different from other pathogens because they cannot reproduce on their own.

Detailed explanation-3: -Finally, you have been introduced to the two smallest types of pathogen – viruses and prions – which are not formed from cells so are not considered to be alive.

Detailed explanation-4: -Prions are simple proteins that are much smaller than viruses. They are unique since they lack a genome. All other known infectious agents contain genetic material. Bacteria are often surrounded by a strong protective cell wall and replicate through simple cell division.

Detailed explanation-5: -ASBV is the smallest known viroid that infects plants and is transmitted by pollen and infected seeds or budwood.