NSF Senior Science Bee Practice Exam

Commensalism is a type of symbiosis where one organism benefits while the other is neither helped nor harmed. This relationship often involves one organism taking advantage of another without causing any detrimental effects. A classic example of commensalism is the relationship between barnacles and whales; barnacles attach themselves to the whale's skin, gaining access to nutrient-rich waters while the whale remains unaffected.

In contrast, mutualism involves a reciprocal benefit to both organisms, such as bees pollinating flowers while obtaining nectar. Parasitism entails one organism benefiting at the expense of another, like a tapeworm living in the intestines of a host and deriving nutrients while harming the host. Competition is a different interaction where organisms vie for the same resources, which generally does not result in a direct benefit to any specific organism. Thus, commensalism uniquely characterizes the one-sided benefit without negatively impacting the other party.