Protists

Of eukaryotic groups, the protists are most commonly unicellular and microscopic. This is a highly diverse group of organisms that are not easy to classify.^[41][42] Several algae species are multicellularprotists, and slime molds have unique life cycles that involve switching between unicellular, colonial, and multicellular forms.^[43] The number of species of protozoa is uncertain, since we may have identified only a small proportion of the diversity in this group of organisms.