What does the protozoan kingdom of the five realms system mean?

Biological taxonomy is a branch of biology, which studies the methods and principles of biological taxonomy. Classification refers to following the principles and methods of taxonomy to name and grade all kinds of organisms. After the Swedish biologist Linnaeus named creatures, later biologists classified them by domain, realm, phylum, class, order, family, genus and species.

The top field, the five fields proposed by Whittaker, is accepted by many people, namely monera, Protozoa, Fungi, Plants and Animals. From the highest "boundary" to "species", the lower the level, the more similar the characteristics of the creatures they belong to.

At present, the most popular classification is the five-realm system, namely monera, Protozoa, Fungi, Plants and Animals. The system of five realms reflects three stages of biological evolution and three branches of multicellular stage, with vertical and horizontal classification. It does not include non-cellular viruses, perhaps because the state of the virus system is unknown. Its protozoan world is complex, including all protozoans and other eukaryotic algae except red algae, brown algae and green algae, including different animals and plants. Example: Zebrafish phylum, family, genus and species: animal kingdom, vertebrate kingdom, bony fish, CYPRINIDAE, CYPRINIDAE, short-billed fish.