Question

“Diatomite” (Kieselguhr) is obtained from
A. Myxophyceae
B. Bacillariophyceae
C. Phaeophyceae
D. Rhodophyceae

Answer 1

Hint: The naturally occurring substance which is a soft, siliceous, and sedimentary rock is called diatomaceous earth or diatomite. The size of the particle ranges from less than 3 µm and more than 1 mm. This powder feels like pumice powder which feels abrasive. The density of diatomite is low whereas porosity is high.

Complete answer: The cell wall surrounds the diatoms. It consists of silica deposits and frustules. Due to the presence of silica, there is a decomposition of highly resistant shells of diatoms. This will deposit in the ocean beds which result in the formation of diatomaceous earth. Kieselguhr is obtained from the extraction, grounding, sieving, and sinteration of diatomaceous earth and used in the technique of filtration. The class of diatoms is Bacillariophyceae.
The absence of cell walls and the presence of various types of morphology at different life stages is the feature of the class Myxophyceae. For example – slime molds.
The class of brown algae is Phaeophyceae. The main feature of this class is alginic acid present in the cell wall with cellulose and further algin obtained. This can be considered as an emulsifying agent and stabilizer as well.
The class of red algae is Rhodophyceae. This can be characterized as the presence of calcium carbonate in the cell wall. The calcium carbonate helps in the permeability of the cell for small molecules and impermeable for macromolecules. The calcium carbonate shells are secreted by red algae which deposit in the bottom of the sea and results in the formation of red corals.
So, the correct answer is “Option B”.

Note:
Thud, diatomite can be referred to as a hard-shelled protist. The granulated form of diatomaceous earth is crushed from the raw material and used in packaging. Diatomite has an abrasive property due to which it can be used as an insecticide. It can also be used for the filtration of swimming pool water, drinking water, etc.