Giardia lamblia is classified as which type of microorganism?

• A. Protozoan
• B. Bacterium
• C. Virus
• D. Fungus

Answer: (A)

Giardia lamblia is a protozoan. Protozoa are single-celled, eukaryotic organisms that often live as parasites in humans. Giardia moves with multiple flagella and exists in two forms: a trophozoite that inhabits the small intestine and a cyst form that is shed in feces and can contaminate water. This makes Giardia a cellular organism with a true nucleus and organelles, unlike bacteria which are prokaryotic and lack a nucleus, and unlike viruses which are acellular particles that require a host cell to reproduce. It’s also distinct from fungi, which are eukaryotic but typically organisms with chitin-containing cell walls and different reproductive and environmental traits.