Question

Write a brief note on cyst formation in protists?

Answer 1

Kingdom protista includes all unicellular eukaryotic microorganism.
Usually, they live as solitary cells but a few forms may develop colonies of similar cells without much cellular differentiation. They are dwelling and live wherever there is water.
The protists are regarded as ancestors of all multicellular eukaryotic organisms.

Complete answer: In protozoan protist asexual reproduction occurs by binary fission or budding. Sexual reproduction occurs by syngamy and conjugation.
1. During unfavorable conditions, some protozoans protists form cysts which help in the penetration and reproduction of the organism.
2. A cyst is the dormant form of the protist. It is an infectious form of protists.
3. It has a resistant cell wall, highly condensed cytoplasm, and low metabolic activity.
4. The cell wall protects the cell from adverse environmental conditions like desiccation, chemicals, low water levels. The low metabolic activity helps the protist to sustain adverse conditions by requiring less amount of energy. When favorable condition returns, excystation takes place releasing more than one organism.

Additional Information: General characteristics of protozoan protists are:
1. Occurence - Protozoan protists have world wide distribution.
They may be aquatic, terrestrial, or parasites.
Parasitic forms cause serious diseases in humans and animals.
2. Form and structure - they are small, microscopic, unicellular, and colorless organisms with varied forms, shapes, and symmetry. The body is naked consists of uninucleate or multinucleate protoplasm bounded by a delicate membrane or a firm pellicle, theca, lorica, or siliceous shell.
3. Locomotion: These protists move with the help of finger-like pseudopodia, whip-like flagella, or short and hairy cilia.
4. Nutrition: The mode of nutrition is holozoic.

Note: Protozoan protists include phylazooflagellata ,sarcodina, sporozoa and cilliata.