ANATOMY

Detailed explanation-1: -Bacteria are the smallest micro-organisms, ranging from between 0.0001 mm and 0.001 mm in size. Phytoplankton and protozoa range from about 0.001 mm to about 0.25 mm. The naked eye can see only the largest phytoplankton and protozoa. Most can only be seen under a microscope.

Detailed explanation-2: -An organism that can be seen only through a microscope. Microorganisms include bacteria, protozoa, algae, and fungi. Although viruses are not considered living organisms, they are sometimes classified as microorganisms.

Detailed explanation-3: -The term “microbe” is used to describe organisms that are too small to be seen with the naked eye. Microbes include bacteria, archaea, fungi, protists, and viruses. Bacteria and archaea are single-celled organisms that do not enclose their genetic material in a nucleus.