Question: 113. Which of following organisms cannot fix nitrogen?
A. Azotobacter
B. Oscillatoria
C. Anabaena
D. Volvox
E. Nostoc
Choose the correct answer from the options given below:
(1) A only
(2) D only
(3) B only
(4) E only
Answer: Option (2)
Explanation:
Nitrogen fixation is the process by which atmospheric nitrogen is converted into usable nitrogenous compounds by certain organisms.
Azotobacter is a free-living nitrogen-fixing bacterium and can fix atmospheric nitrogen.
Oscillatoria is a cyanobacterium capable of nitrogen fixation.
Anabaena is a filamentous cyanobacterium that contains specialized cells called heterocysts for nitrogen fixation.
Nostoc is also a cyanobacterium that can fix atmospheric nitrogen using heterocysts.
Volvox is a green alga and lacks the ability to fix atmospheric nitrogen.
Therefore, the organism that cannot fix nitrogen is Volvox.