Cyanobacteria differ from filamentous algae commonly found in ponds.

• A. They are true algae
• B. They are bacteria, not true algae
• C. They are not true algae and differ from filamentous algae
• D. They are photosynthetic archaea

Answer: (C)

Cyanobacteria are bacteria, not true algae, so they are prokaryotic rather than eukaryotic. This difference in cellular organization is a key way they stand apart from filamentous algae, which are true algae with nucleus-containing cells and chloroplasts. Although cyanobacteria can form filamentous or colony-like structures and perform oxygenic photosynthesis, their place in the bacterial domain means they differ from filamentous algae in both taxonomy and cell biology. That’s why the statement that they are not true algae and differ from filamentous algae best captures the distinction.