What is commensalism?

What is commensalism?

• A. One organism benefits and the other one is not affected
• B. Both organisms benefit
• C. One organism harms the other
• D. Neither organism is affected

Answer: (A)

In commensalism, one organism benefits while the other is not affected. This one-sided benefit fits the idea that the partner gains something (like transport, protection, or access to food) without the other experiencing a positive or negative impact. For example, barnacles on a whale get a ride to nutrient-rich waters and easy access to food particles, while the whale remains neither helped nor harmed in a meaningful way. If both organisms benefited, that would be mutualism; if one benefited and the other was harmed, that would be parasitism. If neither is affected, that’s a neutral interaction.

In commensalism, one organism benefits while the other is not affected. This one-sided benefit fits the idea that the partner gains something (like transport, protection, or access to food) without the other experiencing a positive or negative impact.

For example, barnacles on a whale get a ride to nutrient-rich waters and easy access to food particles, while the whale remains neither helped nor harmed in a meaningful way. If both organisms benefited, that would be mutualism; if one benefited and the other was harmed, that would be parasitism. If neither is affected, that’s a neutral interaction.