Question

Which of the following is not true for Nostoc?
A. Autotrophic
B. Filamentous
C. Macroscopic
D. Prokaryotic

Answer 1

Hint: Nostoc is a cyanobacterium or commonly called as Blue-green Algae. It is like bacteria. They are single celled organisms with no nucleus. They are capable of forming symbiotic relationships with many organisms.

Complete Answer:
- Nostoc is a genus of nitrogen fixing cyanobacteria which are filamentous composed of moniliform cells.. They form microscopic colonies. They form beads like chains that are grouped together as a gelatinous mass. It is found in both aquatic and terrestrial habitats.
- Nostoc does not have a definite nucleus and other membrane bound organelles so they are categorized as prokaryotic organisms. The genetic material is found dispersed in the cytoplasm. They have a thick cell wall which is made up of polysaccharides and polypeptides.
- Nostoc contains pigments called phycocyanin along with the chlorophyll which helps the organism prepare its own food making them autotrophic.
- Nostoc is free living and helps in fixing nitrogen from the atmosphere by forming symbiotic relationships with other organisms.
As given in the question, statements A, B, D are correct.

Thus the correct answer is (C). Nostoc is not macroscopic.

Note: Nostoc is unicellular and lives in community forming chains which gives them an appearance of multicellular organisms. Nostoc is the most primitive organism known till date. The can withstand repeated cycles of freezing and thawing. So they are found in extreme habitats like Polar Regions. The nitrogen fixing ability is an added advantage of this organism.