16Hit1600
Expression of IdeasMediumStating a cause-and-effect relationship

Expression of Ideas practice question

While researching a topic, a student has taken the following notes: - Sea otters eat sea urchins. - Sea urchins graze on kelp. - Where otters were hunted to near-extinction in the 1800s, urchin numbers exploded and kelp forests disappeared. - Where otters have returned, kelp forests have regrown.

The student wants to explain how sea otters affect kelp forests. Which choice most effectively uses relevant information from the notes to accomplish this goal?

  1. A. By eating sea urchins, which graze on kelp, sea otters keep urchin numbers down and allow kelp forests to thrive; where otters vanished, urchins exploded and the kelp disappeared.Correct
  2. B. Sea otters were hunted in the 1800s.
  3. C. Kelp forests have regrown in some places.
  4. D. Sea urchins eat kelp.

Answer: A. By eating sea urchins, which graze on kelp, sea otters keep urchin numbers down and allow kelp forests to thrive; where otters vanished, urchins exploded and the kelp disappeared.

The whole chain: otters, urchins, kelp, and the evidence from the otters' absence.

Why the other answers are wrong

B. Sea otters were hunted in the 1800s.
History without the ecological link.
C. Kelp forests have regrown in some places.
An outcome without the cause.
D. Sea urchins eat kelp.
One link only.

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