Many microscopic organisms had not been studied in detail.
In his time, Carolus Linnaeus only discovered two kingdoms of living things: Animals and Plantae.
In some cases, they were classified together with plants or animals.
German biologist, physician, professor, etc.
However, in 1866, Ernst Haeckel was able to discover a new type of kingdom:
What is Protista?
Protozoa, Algae, Fungi, Bacteria, Other Microorgnisms
A protista is a kingdom of organisms such as the:
Protista are generally simple eukaryotic organisms. Most Protista organisms are unicellular, although some are colonial or multicellular. Protistan organisms are eukaryotic, having a membrane-bound nucleus and endomembrane systems.
CHARACTERISTICS OF PROTISTA
Algae is a plant-like protist capable of photosynthesis.
Two Taxons of Kingdom Protista
Protozoans resemble animals because they can move but cannot produce food. They differ from animals because of their unicellularity.
However, Kaeckel's system wasn't widely accepted.
Yet in present time. Protista is still one of the major kingdoms of organisms.
Scientists continue to classify protozoa as animals and algae as plants.