Protista is a kingdom of single-celled and multicellular eukaryotic organisms.
The kingdom Protista is unique among the six classification kingdoms. If one were to look for a common bond linking all the organisms of this kingdom together it would be difficult to do so. Most of the organisms are unicellular, though many find comfort in grouping together forming colonies. Some are autotrophic, while others are heterotrophic. The main reason these organisms are grouped into the Protista is that they cannot be satisfactorily placed in any of the other kingdoms.
Often called the "trash can" kingdom.
The Protista Kingdom contains a number of organisms previously classified as plants, animals or fungi. E.g. protozoans, all the algae except blue-greens, and several organisms previously called fungi.
Unicellular aquatic Protista (plankton) form a very important component of the food chain. The photosynthetic ones are called phytoplankton and the heterotrophic ones are called zooplankton.
PHYLUMS
CILIOPHORA is the phylum that contains protists that move by cilia, or tiny hair-like structues on the outside of their bodies. One type of cell in this phylum is the Paramecium. These cells can be found in fresh water.
ZOOMASTIGINA is the phylum that moves by flagella, which are whip-like tails. An example of a zooflagellate is the trichonympha collaris, which can be found in the stomach of termites for the purpose of digesting food. Trypanosomes are a type of zooflagellate. They can be found in the tsetse fly. These flies transmit Afican sleeping sickness by biting animals and people.
SPOROZOA is the phylum that contains many disease-causing protists. Plasmodium vivax(which causes a type of malaria) is an example of a sporozoan parasite. Mosquitos are well-known carrier of this disease.
Species
One species in the Protista Kingdom is Trichomonas vaginalis, trichomonas vaginalis is a protozoal parasite infecting humans, adheres to the epithelial layer of the infected urogenital tract and causes trichomonas vaginitis. It's genus name is trichomonas. Its inability to incorporate glycine, formate and bicarbonate into purines [1], as well as aspartate, orotate and bicarbonate into pyrimidines [2], indicates that T. vaginalis lacks purine and pyrimidine de novo biosyntheses. Therefore the parasite acquires the precursors of its nucleic acids by taking up DNA and RNA of lysed host cells and digesting them by its nucleases and phosphatases. Bases are then converted to nucleosides by the nucleoside phosphorylases; however, it remains controversial whether nucleosides are phosphorylated by kinases or phosphotransferases [1–3].
