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Difficulty: MediumPrimary Purpose of the Whole Text

Plant volatile organic compounds (VOCs) were long considered by biologists to be mere byproducts of metabolic stress or simple, direct defenses against herbivores. However, recent research indicates that these airborne chemicals play a sophisticated role in plant-to-plant signaling. When a plant is damaged by herbivores, it releases VOCs that neighboring plants detect. In response, these neighbors prepare their own defenses, such as producing toxins or attracting predatory insects, before they are attacked. This suggests that plants function within a cooperative signaling network rather than as isolated individuals.

Which choice best states the main purpose of the text?

  1. To describe how research has shown that plant volatile organic compounds function as signals that coordinate defense responses among neighboring plants.Answer
  2. B
    To explain the specific biological mechanisms plants use to attract predatory insects when under attack.
  3. C
    To argue that plant-to-plant communication can be harnessed to eliminate the need for chemical pesticides in agriculture.
  4. D
    To dismiss the traditional theory that plants release volatile organic compounds under metabolic stress.

Answer

To describe how research has shown that plant volatile organic compounds function as signals that coordinate defense responses among neighboring plants.
The correct answer accurately states the main purpose of the text, which is to outline how scientific research has demonstrated that volatile organic compounds act as signaling mechanisms that allow neighboring plants to coordinate their defense efforts.

Step-by-Step Solution

1
Analyze the structure of the passage.
The text starts by introducing a traditional view of plant volatile organic compounds as mere byproducts or direct defenses. It then presents a contrast with new research showing these chemicals facilitate plant-to-plant signaling, describing how neighbors respond to these signals by preparing defenses, and concludes that plants operate in a cooperative network.
Understanding the transition from the old view to the new research findings helps identify the overall focus of the text.
2
Evaluate the choices against the entire text.
The option describing how research has shown VOCs function as signals to coordinate defenses is the only choice that captures the main transition and conclusion of the whole text. Other options focus on specific details, introduce outside concepts, or misrepresent the author's stance on the traditional theory.
Evaluating all options ensures that the selected choice matches the primary purpose of the entire passage rather than a local detail or an unsupported generalization.

Key Concept

Identifying the primary purpose of a passage as a whole
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Topics

Primary Purpose of the Whole Text

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