IMMUNOLOGY

Detailed explanation-1: -Bacteria are single celled microbes that lack a nucleus. Archaea are like bacteria, but they have different structures and properties. This gives them the ability to live in extreme environmental conditions.

Detailed explanation-2: -Unicellular organisms are made up of only one cell that carries out all of the functions needed by the organism, while multicellular organisms use many different cells to function. Unicellular organisms include bacteria, protists, and yeast.