Question

Name the transparent siliceous cell wall of Diatoms?

Answer 1

Diatoms are popularly called as photosynthetic protists. These are eukaryotic organisms and are multicellular. These are also called desmids and are included under group Chrysophyta. These diatoms mainly occur in all types of aquatic habitat some of them also persist in moist terrestrial habitats.

Complete answer:
Diatoms: Diatoms are golden brown in color and are photosynthetic protists and are called Chrysophytes (including both diatoms and desmids). They are both aquatic and terrestrial. Some are marine. They support much of marine life. Their important characters are:
These are microscopic organisms that cannot be seen with naked eyes possessing varying colors.
They are basically unicellular but may form pseudo filament and colonies, lacking flagella except in the reproductive stage. They can be present as free-floating (phytoplanktonic); or can be also present as remaining afloat on the surface of water due to the presence of lightweight lipids,
The cellulosic cell wall is always provided with silica to form a transparent siliceous shell, known as a frustule. On the basis of the presence of the symmetry, diatoms may be pennate type, having bilateral symmetry (e.g., Navicula) and centric type, having radial symmetry (e.g., Melosira).
The cell wall is the most preferable characteristic of these organisms and is made up of two halves; one half covering the other (epitheca over hypotheca) resembling a soapbox.
The cell wall encloses in itself the peripheral and outside layer of cytoplasm (primordial utricle) surrounding a large central vacuole.
The nucleus is usually present in the central vacuole, suspended with the help of cytoplasmic strands.
The mode of nutrition is holophytic (photoautotrophic), photosynthetic pigments are chlorophyll a, chlorophyll c, $\beta$-carotene so they also have a green color and special carotenoids containing fucoxanthin; xanthophylls like diatoxanthin, diadinoxanthin.
The reserve food material present inside them is oil and a polysaccharide called leucosis (chrysolaminarin), volutin granules are also present.
They are responsible for almost 50% of the total organic matter synthesized in the biosphere.
Movement occurs by mucilage propulsion.
They mainly undergo asexual reproduction. The common mode of asexual reproduction is binary fission.
During binary fission, one-half of the cell wall is as such remains by each of the daughter cells formed. The other half of the cell wall is secreted the whole new.
Resting spores are called statospores (centric diatoms).
They reproduce sexually as well. Sexual reproduction varies from isogamy to oogamy. It involves gametic meiosis as diatoms are generally diploid (diplontic life cycle).

So, the required answer is frustule.

Note:
Silica shells of dead diatoms are nearly indestructible and not degradable and thus, get assimilated at the sea bed. Such huge rock-like deposits of hard shells of diatoms make possible the presence of diatomaceous earth, which is mined to obtain a whitish powder called diatomite or kieselguhr or diatomaceous earth.