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Difficulty: EasyCentral Ideas

When an acacia tree is browsed by herbivores, such as giraffes, it releases ethylene gas into the air. This airborne chemical signal alerts neighboring acacia trees of the threat, prompting them to rapidly increase production of tannins in their leaves. Tannins are toxic chemicals that make the leaves unpalatable and potentially harmful to herbivores, deterring further feeding. By transmitting these chemical warnings, acacia trees coordinate a collective defense mechanism that helps protect the local tree population from excessive herbivore damage.

Which choice best states the main idea of the text?

  1. Acacia trees can warn neighboring trees of herbivore activity by releasing a chemical gas, triggering a defense response in the surrounding population.Answer
  2. B
    Acacia trees produce tannins to attract giraffes and other herbivores to aid in seed dispersal.
  3. C
    All plants coordinate their defenses against herbivores by releasing ethylene gas.
  4. D
    Giraffes have developed a resistance to the chemical signals released by acacia trees.

Answer

Acacia trees can warn neighboring trees of herbivore activity by releasing a chemical gas, triggering a defense response in the surrounding population.
The correct answer states that acacia trees warn neighboring trees of herbivore activity by releasing a chemical gas, triggering a defense response in the surrounding population. This accurately reflects the passage's description of acacia trees releasing ethylene gas to signal neighboring trees, which then produce tannins to protect themselves.

Step-by-Step Solution

1
Identify the primary subject and the central action described in the text.
The text describes acacia trees releasing ethylene gas when browsed by herbivores, which alerts nearby acacia trees to produce tannins.
This establishes the scope and focus of the passage.
2
Determine the purpose and outcome of the described process.
The release of gas allows trees to coordinate a collective defense (producing tannins) that protects the local population from herbivore damage.
This identifies the overarching theme or central idea of the passage.
3
Evaluate the choices to find the one that best captures this relationship without overgeneralizing or speculating.
The option describing acacia trees warning neighboring trees of herbivore activity to trigger a defense response matches the passage's explanation directly, whereas other options introduce unsupported claims, overgeneralizations, or incorrect details.
This isolates the correct choice based on textual evidence.

Key Concept

Central Ideas
Estimated Time:1m 0s
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