The association between two organisms living together in which only one benefits from the association while the other is neither benefited nor harmed is

1. Analyze the question The question describes a relationship between two organisms living together. One organism benefits, and the other is neither helped nor harmed. You need the term for this type of association.

2. Explain the concept Biological associations are classified by how each partner is affected:

| Relationship | Organism 1 | Organism 2 | |---|---|---| | Mutualism | Benefits | Benefits | | Commensalism | Benefits | Unaffected | | Parasitism | Benefits | Harmed | | Predation | Benefits (feeds) | Killed/harmed | | Competition | Both harmed (compete for limited resources) | Both harmed |

3. Solution: check each option

• A. Predation: One organism hunts and kills another for food. The prey is harmed, so this is wrong.
• B. Competition: Organisms struggle for the same limited resources, so both are negatively affected. This is wrong.
• C. Commensalism: One partner benefits and the other is unaffected. This matches the question exactly.
• D. Dispersal: This is the spreading of seeds or organisms to new areas, not an association between two organisms. This is wrong.

4. Answer The correct option is C. Commensalism.

Examples: an epiphyte (e.g., an orchid) growing on a tree, which gets support and light while the tree is unaffected. Another is egrets following cattle to eat insects the cattle disturb. The cattle are neither helped nor harmed.

5. Exam tip Remember the prefix: com- means "together" and -mensal means "table", so commensals "share a table". Think of "+ / 0": one gains (+), the other is unaffected (0). If the other partner is hurt, it's parasitism (+ / −). If both gain, it's mutualism (+ / +).