Which term best describes an organism that benefits by deriving nutrients from its host?

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

Answer: (C)

Parasitism is a relationship where one organism, the parasite, derives nutrients from another organism, the host, often to the host’s detriment. The organism that benefits by obtaining nutrients from its host is called a parasite. This fits because the parasite gains resources without providing a benefit to the host, and the host is typically harmed or weakened as a result.

This is different from a predator, which gains energy by killing and eating the prey. It’s also different from a mutualist, where both partners benefit. An organism that serves as the source of nutrients for the parasite is the host, not the one benefiting. Examples you might see include fleas feeding on a dog or a tapeworm living in an animal’s intestines. Parasites can live inside the host (endoparasites) or on its surface (ectoparasites), and their relationship to the host can be obligatory or facultative.