Question

Blue green algae are also known as-
A. Eubacteria
B. Cyanobacteria
C. Actinomycetes
D. Archaebacteria

Answer 1

Hint: As you see, blue green algae are not algae at all, as the name suggests. They belong to a certain group of bacteria. They normally look green to blue. They are predominantly aquatic. They are also found in polar regions to adverse climatic conditions.

Complete answer:
Blue green algae are commonly known as cyanobacteria. Their cell wall is surrounded by a mucilaginous sheath made up of pectic acid and mucopolysaccharides. Cyanobacteria contain chlorophyll as well as other photosynthetic pigments. They synthesize their own food with the help of carbon dioxide and water in the presence of sunlight, this process is known as oxygenic photosynthesis. Cyanobacteria possess special types of cells called heterocysts in Nostoc, Anabaena etc. to perform special functions like nitrogen fixation. The gas vacuoles present in them serve to regulate buoyancy in the planktonic forms. This ability to fix atmospheric nitrogen is a very beneficial property to farmers to enrich the soil with nitrogenous components.

Hence the correct option is option B i.e cyanobacteria.

Additional information: The red colour of the red sea is basically due to the large amount of planktonic cyanobacteria present known as Trichodesmium erythraeum. Several cyanobacteria also live in symbiotic association as cycas present in coralloid roots. Some cyanobacteria live in symbiotic association with algae and contribute to soil formation and act as pioneer communities.

Note:
Spirulina, a cyanobacteria is used as a source of protein rich supplement that is being supplied in the form of tablets. This is known as single cell protein. It is beneficial for human diet as well as for some aquatic life.