2025 Biological ClassificationCyanobacteria and Nitrogen Fixation Easy Question 7 of 117 in Biological Classification

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:

A A only
B D only
C B only
D E only

The answer is B.

Solution

Volvox is a green alga (chlorophyte) and cannot fix nitrogen.

Azotobacter, Oscillatoria, Anabaena, and Nostoc are diazotrophs (bacteria/cyanobacteria capable of nitrogen fixation). Volvox is a colonial green alga (eukaryote) that cannot fix atmospheric nitrogen.

Concept Nitrogen Fixing Organisms

Biological Classification in past papers

117 questions from this chapter have appeared across 26 exam years.