Question

Diatomaceous earth is obtained from
(a) Bacillariophyceae
(b) Xanthophyceae
(c) Rhodophyceae
(d) None of the above

Answer 1

Hint: Diatoms and desmids come under group chrysophytes of kingdom protists and the colour of diatoms form due to the presence of pigment xanthophyll, fucoxanthin and diatoxanthin. The diatomaceous earth is formed by the cells of diatoms surrounded by the cell wall.

CompleteAnswer:
Diatoms are the unicellular, photosynthetic organisms which occur in different types of shape. The cell of diatoms is also known as Bacillariophyceae and it is surrounded by the cell wall which consists of cellulose procreated with silica. The upper portion of diatoms is known as epitheca whereas the lower portion is known as hypotheca. It consists of different colour pigments like chlorophyll a and c, xanthophyll, fucoxanthin and diatoxanthin. Due to the presence of silica in the cell wall which is indestructible, so when the diatoms die they leave behind this silica cell wall in the form of diatomaceous earth or diatomites which is porous, rough and gritty useful for commercial purposes.

Additional Information:
Diatomaceous earth most commonly used for polishing, filtration of drugs, oil, syrups and drugs and also in the manufacturing of toothpaste and bricks. Diatoms are a good pollution indicator as it is sensitive to water pollutants therefore in case of water pollution it disappears.

So, the correct answer is 'Bacillariophyceae'.

Note:
Diatomaceous earth is also known as kieselguhr in India and it is used to prepare the water glass also known as sodium silicate which consists of more than 80% of amorphous silica.
Some diatomaceous earth is food grade and it can be consumed by humans which helps to treat problems like constipation, control cholesterol level and also useful to remove dead skin from the skin, but inhalation of diatomaceous earth is dangerous.