Kaplan Nursing Entrance Practice Exam

What describes a relationship where one organism benefits and the other is neither helped nor harmed?

1. Parasitism

2. Mutualism

3. Commensalism

4. Competition

The correct answer is: Commensalism

The relationship where one organism benefits while the other is neither helped nor harmed is known as commensalism. In this type of interaction, one species gains advantages such as food, shelter, or support without negatively affecting the other species involved. A common example of commensalism is barnacles attaching themselves to a whale; the barnacle benefits by getting a place to live and access to food in the water, while the whale remains unaffected by the presence of the barnacles. In contrast, parasitism involves one organism benefiting at the expense of another, resulting in harm to the host. Mutualism is characterized by both organisms benefiting from the interaction, while competition refers to a scenario where two organisms vie for the same resources, which can harm both if resources are limited. Hence, when identifying the relationship that fits the description provided, commensalism is the appropriate choice, as it specifically highlights the benefit to one organism without any detriment to the other.