An organism that lives in or on another organism is called what?

• A. Host
• B. Parasite
• C. Symbiont
• D. Predator

Answer: (B)

Parasitism describes a relationship where one organism benefits by living on or inside another organism, called the host, and uses it for nutrients. The organism doing this is a parasite. The host is the organism that is affected, usually harmed or weakened. A symbiont is any partner in a close association, which can be beneficial, neutral, or harmful, so it’s too broad for this specific scenario. A predator kills and eats its prey, typically not living on or inside it for long-term support, so that term doesn’t fit. An example is a tapeworm inside an animal’s gut or a flea on a dog.