What term describes an organism that lives off another organism?

• A. Parasite
• B. Bacteria
• C. Virus
• D. Fungus

Answer: (A)

Living off another organism describes a parasitic relationship, where one organism—the parasite—derives nutrients and a habitat from a host, often at the host’s expense. This concept covers a wide range of organisms, from tapeworms in the gut to head lice on the scalp, and it emphasizes the dependence of the parasite on the host for survival and reproduction.

Bacteria, viruses, and fungi are broad categories. Some members can be parasites, but they’re not defined solely by living off another organism. Bacteria can be free-living or pathogenic; viruses need a host to replicate but are not universally described as organisms in the same way as parasitic organisms; fungi can be decomposers, mutualists, or parasites. The term that best captures the relationship “lives off another organism” is parasite.