Marine biologist Dr. Sarah Wong studies the decline of kelp forests along the Pacific coast. She argues that the removal of sea otters by hunting in previous centuries allowed sea urchin populations to explode, which then devoured the kelp.
Which evidence would most strongly support Wong's argument about the causal chain?
Kelp forests are home to many marine species
Sea otters were hunted extensively for their fur
Sea urchins eat many types of aquatic plants
Areas where sea otter populations recovered showed 70% kelp forest regrowth within a decade, while otter-free areas showed continued decline
Correct Answer: D
Choice D is the best answer. Recovery experiment proves the causal chain: otters return → kelp returns.
- Context clues: Wong claims otter removal → urchin explosion → kelp decline.
- Evidence evaluation: Otter recovery → kelp recovery proves the chain works in reverse.
- Verify: Comparison to otter-free areas controls for other factors.
💡 Strategy: Causal chain claims are proven when reversing the cause reverses the effect.
Choice A is incorrect because kelp's importance doesn't prove why it declined. Choice B is incorrect because otter hunting history doesn't prove the ecological consequences. Choice C is incorrect because urchin diet doesn't prove they caused the specific decline.