Test: Kingdom Protista- 1 - NEET MCQ

The cell walls construction of diatoms is known as Frustule which consists of two thin overlapping shells fitting into each other just as a soap-box. Their walls are made up of silica. When the diatoms die, the silica in their cell walls gets deposited in the form of diatomaceous earth. This diatomaceous earth is very soft and quite inert. It is used in filtration of oils, sugars, and for other industrial purposes.

Line in NCERT: "In diatoms the cell walls form two thin overlapping shells, which fit together as in a soap box."

• Euglenoids have a protein rich layer called pellicle which makes their body flexible.
• Euglenoids have two flagella that help in their movement.
• Euglena changes its body shape during its movement and this phenomenon called as metaboly is possible due to pellicle.

Line in NCERT: "Instead of a cell wall, they have a protein rich layer called pellicle which makes their body flexible."

Diatoms are unicellular eukaryotes placed under kingdom Protista; option D is incorrect. Cell of Diatoms are surrounded by cell wall having two parts or frustules; frustules make two overlapping halves (the epitheca and the hypotheca). Presence of numerous tiny pores in frustules connects the protoplast of the cell with the outside environment; this makes option A incorrect as their wall are in contact with surrounding water through pores. The pectic substance of cell wall is richly impregnated with silica, which creates patterns of minute perforations and striations. Around 90 percent of diatomaceous cell wall is silica. Shells of diatoms are highly resistant to decomposition due to presence of silica and are deposited in ocean beds leading to formation of diatomaceous earth. This makes option B incorrect and option C correct. Thus, the correct answer is option C. 

Line in NCERT: "The walls are embedded with silica and thus the walls are indestructible."

Cells of diatoms are surrounded by the cell wall, deposited with silica called as frustules which are composed of two overlapping halves (the epitheca and the hypotheca). Shells of diatoms are highly resistant to decomposition due to the presence of silica and are deposited in ocean beds leading to the formation of the diatomaceous earth. This is used as filters because its silica content makes it chemically inactive and uncompressible during insulation.

Line in NCERT: "The walls are embedded with silica and thus the walls are indestructible."

Some examples of decomposer protists are oomycetes, chytrids, labyrinthulomycetes, molds, etc. Oomycetes are fungus-like protists and typically grow on dead animals. Slime molds are also fungus-like protists and are commonly found on rotting logs and compost.

Line in NCERT: "Slime moulds are saprophytic protists. The body moves along decaying twigs and leaves engulfing organic material."

• Red tide is the coloration of water due to very rapid multiplication of red dianoflagellates.
• Chemicals released due to this rapid growth are harmful for aquatic life.

Line in NCERT: "Very often, red dinoflagellates (Example: Gonyaulax) undergo such rapid multiplication that they make the sea appear red (red tides)."

• Diatoms are grouped under Chrysophytes.
• Chrysophytes comprise of golden algae, diatoms and plant like protists etc.
• It’s because of the golden-yellow color of the species they are named as Chrysophytes.

Line in NCERT: "This group includes diatoms and golden algae (desmids)."

Cilia are mostly present in hundreds, projecting out of the holes of the pellicle since basal bodies of all cilia are linked to common kinetodesmata. They beat in the coordinated rhythmic manner to produce paddle stroke effect. Due to their occurrence all over the body, they perform the fastest locomotion i.e., 400-2000 micrometer/second. So, they are the most efficient organs of locomotion.

Line in NCERT: "Ciliated protozoans: These are aquatic, actively moving organisms because of the presence of thousands of cilia."