The units of selection debate asks at what level natural selection operates. Genic selectionists argue genes are the fundamental replicators; organisms are 'vehicles' for gene propagation. Organism-level selectionists argue that organisms, not genes, face environmental challenges and reproduce. Multi-level selection theorists argue selection can operate at multiple levels simultaneously—gene, organism, and group—with different levels dominating in different circumstances.
The passage suggests that
all evolutionary biologists agree selection operates only at the gene level
organism-level and gene-level selection are identical concepts
scientific questions about the level of analysis can generate substantive theoretical disagreements
multi-level selection has been universally rejected
Correct Answer: C
Choice C is the best answer. The level of selection is substantively disputed.
- Context clues: Gene-level, organism-level, and multi-level selectionists offer different theories.
- Meaning: Different level choices yield different theoretical frameworks.
- Verify: The persistence of debate shows genuine theoretical disagreement.
💡 Strategy: When different levels of analysis generate competing theories, infer substantive disagreement.
Choice A is incorrect because organism-level and multi-level selectionists disagree. Choice B is incorrect because they're presented as contrasting positions. Choice D is incorrect because multi-level selection theory is presented as a current option.