In which type of association do one organism benefit while the other is neither helped nor harmed?

• A. Mutualism
• B. Commensalism
• C. Parasitism
• D. Competition

Answer: (B)

In commensalism, one organism benefits while the other is neither helped nor harmed. This type of association is characterized by the presence of one species that gains some benefit, such as shelter, food, or transportation, from another species without affecting it negatively or positively. A classic example of commensalism would be barnacles attaching themselves to the shell of a turtle. The barnacles gain access to a wider range of nutrients as the turtle moves through different environments, while the turtle remains unaffected by their presence.

In contrast, mutualism involves both organisms benefiting from the association, as in the case of bees and flowers where bees obtain nectar while aiding in pollination. Parasitism, on the other hand, describes a relationship where one organism benefits at the expense of the other, such as fleas feeding on a dog. Lastly, competition occurs between organisms when they vie for the same resources, leading to potential harm to both as they compete for limited resources like food or space. Thus, the defining characteristic of commensalism is the unidirectional advantage it provides to one organism without causing any impact on the other.