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Difficulty: EasyPrimary Purpose of the Whole Text

For decades, biologists debated why zebras have distinctive black-and-white stripes, suggesting hypotheses ranging from camouflage in tall grass to social bonding. Recent research by Caro and colleagues, however, suggests a more practical explanation: the stripes deter biting flies. By observing horses dressed in striped coats and comparing them to undecorated horses, researchers found that horseflies flew toward both targets at similar speeds but failed to decelerate properly before landing on the striped surfaces, often bouncing off instead. This indicates that the contrasting pattern disrupts the flies' visual systems during their final approach, offering zebras an evolutionary advantage against disease-carrying insects.

Which choice best states the main purpose of the text?

  1. A
    To describe the experimental procedure of dressing horses in striped coats.
  2. To present research findings that explain how zebra stripes deter biting flies.Answer
  3. C
    To debate the various historical hypotheses about the evolutionary function of zebra stripes.
  4. D
    To suggest that horseflies prefer landing on striped surfaces over solid ones.

Answer

The correct answer is the option that states the text's purpose is to present research findings that explain how zebra stripes deter biting flies.
The correct answer accurately summarizes the main objective of the passage. The text introduces recent research showing that zebra stripes deter flies, explains the experiment supporting this, and concludes with how this benefits zebras. Thus, the primary purpose is to present findings explaining this phenomenon.

Step-by-Step Solution

1
Identify the main topic of the passage.
The passage discusses recent research demonstrating that zebra stripes prevent biting flies from landing.
Understanding the core topic provides the foundation for finding the primary purpose of the whole text.
2
Analyze how the author structures and develops this topic.
The author contrasts past debates with new research, describes a simple experiment testing the theory, and explains the visual mechanism behind the fly-deterring effect.
Examining the structure helps distinguish the main point of the passage from supporting details.
3
Select the choice that best encapsulates the entire passage without focusing too narrowly or contradicting the text.
The statement about presenting research findings on how stripes deter flies captures the main point, whereas other choices focus too much on a single detail, misidentify the main focus, or contradict the text.
The primary purpose must reflect the text as a whole rather than a single paragraph or detail.

Key Concept

Primary Purpose of the Whole Text
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Primary Purpose of the Whole Text

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