Question
Biology Question on biological classification
In Aulosira, Tolypothrix and Nostoc, _______ are the sites for nitrogen fixation.
A
vesicles
B
arbuscles
C
akinetes
D
heterocysts
Answer
heterocysts
Explanation
Solution
Many cyanobacteria are free living and filamentous such as Aulosira, Tolypothrix, Nostoc, etc. These cyanobacteria have some specialised and colourless cells, called heterocysts which are the sites of nitrogen fixation.