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Difficulty: EasyCentral Ideas

Sea otters play a critical role in maintaining the health of coastal marine ecosystems, particularly kelp forests. Kelp forests provide vital habitat and food for numerous marine species, but they are highly vulnerable to overgrazing by sea urchins. By feeding on sea urchins, sea otters prevent these herbivores from decimating the kelp. In areas where sea otters have been removed, urchin populations have erupted, leading to the widespread destruction of kelp forests and a subsequent decline in biodiversity. Consequently, the presence of sea otters is essential for preserving the structure and ecological balance of these coastal habitats.

Which choice best states the main idea of the text?

  1. A
    Predators are the primary drivers of health and biodiversity in all marine ecosystems.
  2. B
    Sea otters damage kelp forests by helping sea urchin populations grow.
  3. Sea otters protect kelp forests from destruction by keeping sea urchin populations in check.Answer
  4. D
    Sea urchins would likely go extinct if sea otters did not continuously prey on them.

Answer

Sea otters protect kelp forests from destruction by keeping sea urchin populations in check.
The correct answer accurately states that sea otters protect kelp forests from destruction by keeping sea urchin populations in check. The passage explains that sea urchins eat kelp and that sea otters feed on sea urchins, thereby preventing them from destroying the kelp forest. When sea otters are absent, urchin populations increase and decimate the kelp, illustrating that sea otters are vital to the ecosystem's balance.

Step-by-Step Solution

1
Analyze the text for its primary subject and the author's main claim.
The text discusses sea otters, sea urchins, and kelp forests, claiming that sea otters are essential for preserving these coastal habitats.
Identifying the subject and claim is the first step in determining the central idea.
2
Examine how the relationships between the species support the main claim.
Sea urchins destroy kelp forests, and sea otters eat sea urchins, which protects the kelp.
Understanding these interactions explains why sea otters are essential to the ecosystem.
3
Select the choice that accurately summarizes this relationship as the central message of the passage.
The statement that sea otters protect kelp forests from destruction by keeping sea urchin populations in check is the correct summary.
This option captures the overall argument of the text without overgeneralizing or speculating.

Key Concept

Central Ideas
Estimated Time:1m 0s
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