Which statement describes parasitism?

• A. Parasite benefits, host harmed
• B. Host benefits, parasite harmed
• C. Both species benefit
• D. Neither benefits

Answer: (A)

Parasitism is a one-sided relationship where the parasite gains resources, habitat, or a means of reproduction by using the host, often harming the host in the process. The parasite’s success depends on exploiting the host, which can reduce the host’s fitness or health. Examples like tapeworms in the gut, fleas on a mammal, or the Plasmodium parasite causing malaria illustrate this dynamic. This is different from mutualism, where both partners benefit, or commensalism, where the host is unaffected. So the statement that the parasite benefits while the host is harmed best captures parasitism.