Members of the kingdom Protista are single (eukaryotic) celled organisms. Unlike
monarians, protistans have a nucleus which contains chromosomes, rather than just
the scattered chromatin which is found in bacteria. Protistans include single-celled organisms that are like fungi, single-celled organisms that are like
plants, and single-celled organisms that are like animals.
The word "phyto" means plant-like. The word "zoo" means animal like. The protistan known as Plankton, like other protistans, can be either of these. Phytoplankton are photosynthetic autotroph which live in the sea. They produce more breathable oxygen than all land-bound plants put together. Zooplankton are animal-like and are non-photosynthetic heterotrophs.
Another very common protistan are the Eugenia. Euglena have flagella which they use to move about. Their cell is surrounded and protected by a tough pellicle which is made from a protein. Most euglena live in fresh water. They are photosynthetic and have an eye spot which is used to find light.
Another group of protistan, the chrysophytes, are commonly called Golden Algae. Chrysophytes have scales made of silica which contain a substance called fucoxanthin. It is the yellow fucoxanthin which blends with the green chlorophyll to give them their golden color. Most chrysophytes live in water and have flagella which allows them to move about. However, there is one kind of chrysophyte which lacks flagella called Diatoms. Diatoms have a double wall made of silica. When they die, they form diatomaceous earth which is used to make glass polish, and is used to make air and water filters.
Another group of protistans are the Dinoflagellates. They are distinguished by having two flagella which are perpendicular to each other. Having two flagella allows them to make more precise movements. The Dinoflagellate called Gonyaulax produces a powerful neuro-toxin which kills fish and shrimp. Gonyaulax is red in color and causes "red tide" which often covers hundreds of miles of coastline.
While most Eugenia, Chrysophytes and Dinoflagellates are usually photosynthetic, another group of protistans called protozoans are not. Most protozoans are parasites or predators. The protozoan Trypanosoma brucei causes African Sleeping Sickness. This parasite it transmitted to man by the bite of the tsetse fly. Another protozoan, Entameba histolytica is a parasite of the stomach which kills cells and drinks blood. They cause stomach aches and diarrhea, but are "good" parasites and do not actually kill the host. The protozoan Plasmodium virrax causes malaria. This protozoan is carried by the female anopheles mosquito. Amoeba are another common protozoan which move by means of pseudopodia (false feet).
Most protozoans move by means of pseudopodia and by cilia. Cilia are like
flagella, except they are shorter and there are many of them.