What is Protista Kingdom?
The Protista kingdom comprises all unicellular eukaryotes. The kingdom Protista has unclear boundaries, as it is difficult to define the single-celled eukaryotes clearly.
Members of this kingdom are primarily aquatic and form a link between fungi, plants, and the Animalia kingdom.
Organisms belonging to this group contain a well-defined nucleus and other membrane-bound organelles. Flagella or cilia may be present for locomotion. Online Tutorspoint provides Kingdom Protista Assignment Help
Protists do not develop from embryo-like plants nor do they develop from zygote-like animals. Protists reproduce sexually and asexually by a process involving cell fusion and the formation of a zygote. Among the members of the Protista kingdom, the algae resemble most of the characteristics of plants and euglenoids resemble both plant and animal characteristics. Hence protozoans are of special interest to biologists.
A. Chrysophytes:
1. This group includes organisms like diatoms and golden algae (desmids). Diatoms are present abundantly in oceans.
2. Microscopic, found in freshwater and marine water, floating passively in water currents
3. Photosynthetic autotrophic organisms
4. The cell walls of diatoms are embedded with silica and overlap with each other, thus making them indestructible.
5. Accumulation of the cell wall deposits in the habitats of diatoms form ‘diatomaceous earth’ which can be used for polishing, and filtration of oils and syrups.
B. Dinoflagellates:
1. Mostly marine and photosynthetic
2. The color of the organisms depends on the pigments present in their cells. They usually appear in yellow, green, red, brown, or blue.
3. Presence of stiff cellulose plates on the outer surface of the cells.
4. Usually, two flagella are seen, one lies longitudinally, and the other is transversely set between the two cellulose plates.
5. Toxins produced by these organisms can kill other marine organisms nearby.
C. Euglenoids
1. Freshwater organisms found in stagnant water
2. Most of the time euglenoids are photosynthetic but under unfavorable conditions, they behave as heterotrophs feeding on other small organisms.
3. Presence of a protein-rich layer, which makes their body flexible
4. Two flagella are seen – a short one and a long one.
5. Presence of pigments in the cells which are identical to pigments of higher plants.
D. Slime Moulds
1. Saprophytes living on dead and decaying organic matter.
2. During favorable conditions, slime molds are used to aggregate to form plasmodium on host feet. This Plasmodium, under unfavorable conditions, used to bear spores and fruiting bodies that used to enable their reproduction cycle.
3. The spores possess true walls, are extremely resistant, and are dispersed through an air medium.
E. Protozoan
1. Heterotrophs are believed to be a primitive relative of animals
Amoeboid Protozoans: Live in fresh water and sea and capture their prey with the help of pseudopodia (false feet). The presence of silica is observed on their shells.
Flagellated Protozoans: As the name suggests that the presence of flagella. Members of this group are either free-living or parasitic, which causes diseases like sleep sickness. For example., Trypanosoma
Ciliated Protozoans: Presence of cilia for locomotive activity. Presence of a cavity (gullet) that opens on the outer surface of the body
Sporozoans: Members of this group are diverse and have an infectious spore-like stage. For example, Plasmodium is most notorious for causing malaria in the human population.