Question

Armoured cell wall and biflagellated cells are characteristic of
A. Bascillariophyta
B. Pyrrophyta
C. Euglenophyta
D. Cyanophyta

Answer 1

Hint: Flagella are structures which help in the movement. These are generally present in unicellular organisms. The cell wall is a continuous layered structure but the armoured type cell wall is present in a small plate forming a multilayer structure. Such an armoured cell wall structure can be seen in fire algae.

Complete answer:
Armoured cell walls and flagellated cells are characteristic of Pyrrophyta. Pyrrophyta is a unicellular alga with two types of flagella, i.e. biflagellated. The two flagella lie perpendicular to each other due to which it moves in a rotatory motion. The cell wall is made up of cellulose which is not present in a continuous form but the number of plates forms an armoured-like structure. Hence, Pyrrophyta is the algae with the armoured cell wall and biflagellated cells.
i. Bacillariophyta: It is also known as a diatom and is found mainly in marine water in the benthic zone. In unicellular algae (microalgae), cell walls are made of silica forming a soap box-like structure called a frustule. Frustules is a hard and porous cell wall made up of silicic acid that consists of two-parts; larger part called hypotheca and a smaller part called epitheca. These are nonmotile and have no flagella.
ii. Euglenophyta: These are single-celled organisms without a cell wall. A proteinaceous covering called pellicle is present. These are motile because a single flagellum is present.
iii. Cyanophyta: These are photosynthetic bacteria also known as blue-green algae. They perform photosynthesis and release oxygen as a by-product. These are motile, but flagella are absent. The cell wall is made up of gelatin.

Note: Organism with flagella is called flagellated. It refers to all mono flagellates (with one flagellum), biflagellate (with two flagella), or multiflagellate (with many flagella). The armoured cell wall is related to the overall structure, not the cell wall material.