In ecology, which term describes the interaction in which one species benefits from the relationship while the other species is neither harmed nor helped, remaining essentially unaffected?

Introduction / Context:
Ecology studies how organisms interact with each other and with their environment. Relationships between species can be positive, negative, or neutral in their effects. Understanding the different types of interactions, such as predation, parasitism, mutualism, and commensalism, is a common topic in school level biology and general knowledge exams. This question asks you to identify the specific term for an interaction where one species benefits while the other is neither harmed nor helped.

Given Data / Assumptions:

• The interaction involves two species living in association.
• One species clearly benefits from the relationship.
• The other species is neither harmed nor benefited and remains effectively neutral.
• Options include commensalism, predation, competition, parasitism, and mutualism.
• We assume standard definitions from ecology textbooks.

Concept / Approach:
In commensalism, one species gains an advantage, such as food, shelter, or transportation, while the other species experiences no significant positive or negative effect. A classic example is barnacles attaching to the shell of a turtle or the skin of a whale; the barnacles gain a place to live and increased access to food particles, whereas the host is usually unaffected. This contrasts with mutualism, where both species benefit, and parasitism, where one benefits at the expense of the other. Predation involves one organism killing and eating another, and competition occurs when both species are negatively affected by limited resources. Thus, the correct term for benefit neutral relationships is commensalism.

Step-by-Step Solution:
Step 1: Identify that one species benefits from the relationship. Step 2: Note that the second species is neither harmed nor helped, meaning the effect on it is neutral. Step 3: Recall that commensalism is defined as a relationship where one species benefits and the other is unaffected. Step 4: Contrast this with mutualism, in which both species benefit from the relationship. Step 5: Recognise that in parasitism, one species benefits while the host is harmed. Step 6: Remember that predation involves one organism killing another for food, clearly harming one and benefiting the other. Step 7: Understand that competition results in both species experiencing some negative effect due to shared limited resources. Step 8: Conclude that commensalism best fits the description in the question.

Verification / Alternative check:
Ecology diagrams often use notation such as plus, minus, or zero signs to summarise interactions. Commensalism is represented as (+, 0), mutualism as (+, +), parasitism and predation as (+, −), and competition as (−, −). The pattern described in the question matches the (+, 0) case. Examples like epiphytic plants growing on trees, where the epiphyte gains a higher position for light while the tree is largely unaffected, are labelled as commensalism in textbooks. This supports the choice of commensalism as the correct answer.

Why Other Options Are Wrong:
Predation: The predator benefits but the prey is killed or harmed, so the interaction is not neutral for one partner. Competition: Both species suffer reduced growth, reproduction, or survival because they compete for the same resource. Parasitism: The parasite benefits while the host is harmed, which does not match the neutral effect described. Mutualism: Both species benefit, whereas the question clearly states that only one species benefits.

Common Pitfalls:
Students sometimes confuse commensalism with mutualism because both relationships involve at least one species benefiting and no immediate killing. The key difference is whether the second species gains an advantage. If both do, it is mutualism; if only one benefits and the other is unaffected, it is commensalism. Another pitfall is to focus on the example rather than the definition, so make sure you always return to the basic benefit neutral pattern when identifying commensalism.

Final Answer:
The interaction in which one species benefits and the other is neither harmed nor helped is called commensalism.