Wildlife biologist Dr. Karen Smith argues that reintroducing wolves to Yellowstone National Park transformed the entire ecosystem. She claims wolves changed elk behavior, which allowed riverside vegetation to recover, stabilizing stream banks.
Which observation would best support Smith's argument about ecosystem-wide effects?
Wolves are social animals that hunt in packs
After wolf reintroduction, elk began avoiding certain riverbanks where they were vulnerable to predation; willow trees there grew 400% taller, bird populations tripled, and stream channels became narrower and deeper
Yellowstone receives millions of visitors annually
Elk populations have fluctuated throughout the park's history
Correct Answer: B
Choice B is the best answer. Complete causal chain: wolves → elk behavior → vegetation → streams → birds.
- Context clues: Smith claims ecosystem-wide transformation through a chain of effects.
- Evidence evaluation: Each link in the chain is documented with specific metrics.
- Verify: 400% willow growth, 3x birds, changed streams proves cascading effects.
💡 Strategy: Ecosystem claims need evidence of connected changes across multiple components.
Choice A is incorrect because wolf behavior doesn't prove ecosystem effects. Choice C is incorrect because tourism numbers don't address ecological impacts. Choice D is incorrect because natural fluctuation doesn't prove wolf-caused changes.