Which term describes the relationship where the parasite benefits and the host is harmed?

• A. Parasitism
• B. Mutualism
• C. Commensalism
• D. Predation

Answer: (A)

Parasitism is a relationship where one organism gains resources and benefits at the expense of another. The parasite thrives by feeding on the host, obtaining nutrients, habitat, or a means of transport without giving anything back. The host, meanwhile, incurs costs—reduced energy for growth or reproduction, tissue damage, or heightened susceptibility to disease. This setup is distinct from mutualism, where both partners benefit; commensalism, where one benefits and the other is largely unaffected; and predation, where one organism kills and consumes another. So, the term that best describes a parasite benefiting while the host is harmed is parasitism.