The type of association in which one organism benefits and the other neither benefits nor is harmed is called

Step 1: Analyze the question The question describes a relationship between two organisms where one benefits (+) and the other is unaffected (0). We need the term for a +/0 relationship.

Step 2: Explain the concepts

| Term | Effect on Organism 1 | Effect on Organism 2 | |---|---|---| | Commensalism | Benefits (+) | Neither benefits nor harmed (0) | | Mutualism | Benefits (+) | Benefits (+) | | Parasitism | Benefits (+) | Harmed (−) | | Saprophytism | Feeds on dead or decaying matter | No living partner involved | | Symbiosis | General term for close living together, including mutualism, commensalism and parasitism | |

Step 3: Work through the options

• A. Commensalism: One partner gains and the other is unaffected. This matches the description.
• B. Mutualism: Both partners benefit, so it does not fit.
• C. Parasitism: The host is harmed, so it does not fit.
• D. Saprophytism: This is feeding on dead organic matter, not an association between two living organisms.
• E. Symbiosis: This is a broad term. Not all symbiosis is +/0, so it is not specific enough.

Step 4: Answer The correct answer is A. commensalism.

Examples: Orchids or epiphytic ferns growing on tree trunks (they get support and light, and the tree is unaffected), and egrets following cattle (they eat insects the cattle disturb, and the cattle are unaffected).

Exam tip: Remember the prefix "com-" as meaning "sharing a table." One partner eats, and the other does not mind. You can also use signs: Commensalism = +/0, Mutualism = +/+, Parasitism = +/−.