The cell walls of diatoms are called frustules. The cell wall is chiefly composed of cellulose impregnated with glass – like silica. It is composed of two overlapping halves (or theca) that fit together like two parts of a soap box or petri dish. The upper half (lid) is called epitheca and the lower half (case) is called hypotheca. The outer covering possesses very fine markings, pits, pores and ridges. The siliceous frustules of diatoms do not decay easily. They pile up at the bottom of water reservoirs and form big heaps called diatomite or diatomaceous earth. It may extend for several hundred metres in certain areas from where the same can be mined.Answered by Pragya Singh | 1 year ago
Organise a discussion in your class on the topic – Are viruses living or nonliving?
Give a brief account of viruses with respect to their structure and nature of genetic material. Also name four common viral diseases.
What are the characteristic features of Euglenoids?
Give a comparative account of the classes of Kingdom Fungi under the following:
(i) mode of nutrition
(ii) mode of reproduction
What do the terms phycobiont and mycobiont signify?