The association between a tapeworm and an infected mammal illustrates

Step 1: Analyze the question The question asks what type of relationship exists between a tapeworm and a mammal it has infected.

Step 2: Key concept Different biological associations are defined by who benefits and who is harmed:

• Commensalism: one organism benefits, the other is neither helped nor harmed.
• Parasitism: one organism (the parasite) benefits and the other (the host) is harmed.
• Predation: one organism kills and eats another.
• Saprophytism: an organism feeds on dead or decaying organic matter.
• Symbiosis: a broad term for organisms living together. It often implies mutual benefit, as in the nitrogen-fixing bacteria in legume root nodules.

Step 3: Apply to the tapeworm

• The tapeworm (e.g., Taenia solium) lives in the intestine of its host.
• It absorbs the host's digested food directly, so it benefits.
• The host loses nutrients and may suffer weight loss, weakness, and malnutrition, so it is harmed.
• The host is not killed and eaten, so this is not predation.
• The host is alive, so this is not saprophytism.
• One party benefits and the other is harmed, so this is not commensalism.

Step 4: Symbiosis or parasitism? Parasitism is technically a type of symbiosis, but in NECO and WASSCE questions "symbiosis" usually means a mutually beneficial relationship. Parasitism is the most specific and accurate term, so it is the best answer.

Answer: B. parasitism

Exam tip: Remember the pattern "+/−" for parasitism: the parasite gains (+) and the host loses (−). When two options are both technically true, choose the more specific one. Other common parasites to remember are the tick, the flea, Plasmodium, and the roundworm.