I think protists (like the amoeba) are considered a fourth kingdom within the eukaryotes. But that isn't even the highest level of classification: eukaryotes ar

I think protists (like the amoeba) are considered a fourth kingdom within the eukaryotes. But that isn't even the highest level of classification: eukaryotes are only one of three domains of life, the other two being bacteria and archaea. (Eukaryotes are believed to have originated as symbiotic unions of ancestors of archaea and bacteria.)