An amoeba, paramecium,and cryptosporidium are all examples of protozoa type of microorganism.
The term protozoa is used to denote single-celled eukaryotes. All of them (amoeba, paramecium,and cryptosporidium) are single-celled eukaryotes. They all possess a “true,” or membrane-bound, nucleus and are nonfilamentous (in contrast to organisms such as molds, a group of fungi, which have filaments called hyphae).