Why is the term 'algae' misleading when referring to cyanobacteria?

• A. Cyanobacteria are true algae
• B. Cyanobacteria are bacteria, not true algae
• C. Cyanobacteria are not true algae and differ from filamentous algae common in ponds
• D. Cyanobacteria are photosynthetic archaea

Answer: (C)

Cyanobacteria are bacteria, not algae. Algae are eukaryotic photosynthetic organisms with a nucleus and organelles like chloroplasts, while cyanobacteria are prokaryotes lacking those features. This fundamental difference means calling cyanobacteria “algae” is misleading, even though they can resemble filamentous algae in appearance and form blooms. Filamentous algae common in ponds are true algae (eukaryotic) and have cellular organization with chloroplasts and more complex cell structures, which cyanobacteria do not. So, the term is misleading because it mixes two very different groups: cyanobacteria are photosynthetic bacteria, not the true algae.