ANATOMY

Detailed explanation-1: -Single-celled organisms are called unicellular organisms. All prokaryotic organisms such as Bacteria, Archaea are unicellular. A single cell performs all functions such as metabolism, excretion and reproduction.

Detailed explanation-2: -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. Protozoa are unicellular microorganisms that have nuclei.

Detailed explanation-3: -Bacteria lack a membrane-bound nucleus and other internal structures and are therefore ranked among the unicellular life-forms called prokaryotes.

Detailed explanation-4: -Prokaryotes. Prokaryotes are unicellular organisms without a true nucleus. They are very small in size from 0.1 to 5.0 µm.