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Difficulty: EasyPrimary Purpose of the Whole Text

In marine ecosystems, kelp forests provide critical habitat for numerous marine organisms. However, these vital habitats are frequently threatened by sea urchins, which consume kelp at a rapid rate. Sea otters play a crucial role in maintaining the balance of these ecosystems by preying on sea urchins, thereby preventing the overgrazing of kelp forests. Without sea otters, kelp forests would quickly collapse, leading to a significant loss of biodiversity in the region. Thus, the presence of sea otters is essential to the health and stability of the entire coastal marine ecosystem.

Which choice best states the main purpose of the text?

  1. A
    To argue that all marine ecosystems are threatened by a lack of biodiversity.
  2. B
    To describe the rate at which sea urchins consume kelp in marine environments.
  3. To explain how sea otters play a vital role in maintaining the balance of coastal marine ecosystems.Answer
  4. D
    To suggest that kelp forests are the only habitats capable of supporting sea otters.

Answer

The main purpose of the text is to explain how sea otters play a vital role in maintaining the balance of coastal marine ecosystems.
The correct option accurately identifies the primary purpose of the text. The passage describes the symbiotic and predatory relationships within a coastal kelp forest ecosystem, specifically highlighting how sea otters prevent sea urchins from destroying kelp. The author concludes that sea otters are essential to the stability of the entire ecosystem, making the explanation of their vital role the main focus of the text.

Step-by-Step Solution

1
Analyze the structure of the passage
The text begins by introducing kelp forests as crucial habitats, identifies sea urchins as a threat to these habitats, explains how sea otters mitigate this threat by preying on urchins, and concludes by stating that sea otters are essential to the overall health of the ecosystem.
Understanding the flow of ideas helps identify the overarching goal of the author.
2
Determine the primary focus of the text as a whole
The author focuses on the trophic cascade where sea otters control urchin populations to save kelp forests, illustrating the otters' necessary role in the ecosystem.
The primary purpose must encapsulate the main claim or explanation of the entire passage rather than a minor detail.
3
Evaluate the choices against the primary focus
The choice describing sea otters playing a vital role in maintaining ecosystem balance directly summarizes the entire text, while other options either overgeneralize, focus on minor details, or misrepresent the facts in the text.
This isolates the correct choice and explains why the distractors are incorrect.

Key Concept

Primary Purpose of the Whole Text
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Topics

Primary Purpose of the Whole Text

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