Question

What was the old name of Blue green algae?
A. Cyanobacteria
B. Myxophyceae
C. Spectrum algae
D. None of the these

Answer 1

Hint: Due to the ability to produce food and the presence of pigment cyanobacteria is compared with algae. Chlorophyll a and phycobilins are pigments that give blue-green colour to cyanobacteria.

Complete Answer:
- There are thousands of different eubacteria or true bacteria. Most of them are characterised by the presence of rigid cell walls, and if motile, a flagellum. Cyanobacteria is also a Eubacteria.
- Cyanobacteria are Gram-negative photosynthetic prokaryotes, being the most primitive organisms to have oxygenic photosynthesis. They added oxygen to the atmosphere, which is indispensable for the existence of aerobic forms of living organisms.
- Cyanobacteria perform photosynthesis with the help of chlorophyll-a but it has other pigments that also play role in photosynthesis like phycocyanin that impart blue colour, phycoerythrin that important red colour and allophycocyanin that is responsible for light blue coloured due to these pigments cyanobacteria is blue-green in colour hence they also known as blue-green algae.
- Cyanobacteria can be classified variously under Cyanophyceae or myxophyceae. Myxophyceae is a type of cyanobacteria.

So the correct option is (A).

Additional Information:
Cyanobacteria are mainly freshwater forms, though few are marine. Cyanobacteria may be unicelled, filamentous and colonial. The filamentous form consists of one or more cellular strands, called trichomes, surrounded by a mucilaginous sheath. Cyanobacteria are characterised by the presence of flagellum throughout the life cycle.

Note:Gaidukov's phenomenon or complementary chromatic adaptation-Cyanobacteria or blue-green algae can adaptively change their body colour according to different wavelengths of available light, e.g., Trichodesmium erythraeum. It is also known as “red sea” causing algae.