Question

which symbiotic interaction involves one organism feeding on or within another organism which is positive for one side of the interaction but negative for the other side?
competition
mutualism
commensalism
parasitism

Explanation:

• Competition: It is about organisms competing for resources like food, space. It doesn't involve one feeding on another in the described positive - negative way.
• Mutualism: Both organisms benefit from the interaction. For example, bees and flowers (bees get nectar, flowers get pollinated). So it's not the case here.
• Commensalism: One organism benefits and the other is neither helped nor harmed. Like barnacles on whales (barnacles get a place to live, whales are unaffected). Not the right fit.
• Parasitism: One organism (parasite) feeds on or within another organism (host). The parasite benefits (gets food, shelter etc.) and the host is harmed (loses nutrients, may get sick). This matches the description of positive for one side (parasite) and negative for the other (host).

Answer:

parasitism