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Question

Difficulty: MediumDistinguishing Main Ideas from Supporting Details

Passage

In 2009, researchers off the coast of Indonesia documented a remarkable behavior in the coconut octopus (*Amphioctopus marginatus*). The creature was observed excavating discarded coconut shells, carrying them beneath its body while walking awkwardly across the seafloor, and later assembling them into a protective shelter. This marked the first clear evidence of tool use in an invertebrate. Historically, biologists reserved the definition of tool use for animals that manipulate objects to achieve a future goal, a cognitive feat thought to be unique to vertebrates like primates and birds. The octopus's behavior, termed 'extrapolative tool use,' challenges this evolutionary assumption by showing that complex spatial reasoning and goal-directed planning can arise in organisms with completely different neural architectures. While some critics argue that the behavior is merely a sophisticated reflex or a form of play, the deliberate selection, transport, and assembly of the shells suggest a level of foresight previously unrecognized in mollusks. By demonstrating that cognitive complexity does not require a vertebrate brain, *Amphioctopus marginatus* has forced evolutionary biologists to re-evaluate the origins of intelligence.

Which of the following statements best summarizes the main idea of the passage?

  1. A
    Invertebrates possess cognitive abilities and neural structures that are far superior to those of primates and birds.
  2. B
    The coconut octopus walks across the seafloor carrying discarded coconut shells to use as protective shelters.
  3. The tool-using behavior of the coconut octopus challenges traditional evolutionary assumptions by demonstrating complex cognitive abilities in an invertebrate.Answer
  4. D
    Biologists have concluded that the behavior of the coconut octopus is a sophisticated reflex rather than goal-directed planning.

Answer

The statement that the tool-using behavior of the coconut octopus challenges traditional evolutionary assumptions by demonstrating complex cognitive abilities in an invertebrate best summarizes the main idea.
The correct answer accurately captures the main idea of the passage: the tool-using behavior of the coconut octopus challenges the long-held evolutionary assumption that complex spatial reasoning and goal-directed planning are unique to vertebrates.

Step-by-Step Solution

1
Analyze the passage structure and identify the author's primary thesis.
The passage begins with a specific biological observation (the coconut octopus using shells) and transitions to a broader thesis: that this behavior challenges assumptions about the uniqueness of vertebrate cognition.
Identifying where the author shifts from narrative detail to structural argument helps separate supporting evidence from the main thesis.
2
Differentiate the central argument from supporting details.
The description of the octopus walking with shells is a supporting detail. The reference to critics' views is a minor counter-argument. The core claim is that invertebrate intelligence challenges existing scientific definitions of tool use and brain structure.
Distinguishing the central claim prevents selecting distractors that are true details but do not capture the global focus of the passage.
3
Evaluate the choices to find the one that encompasses the entire text's significance.
The correct option correctly states that the behavior of the octopus challenges traditional views by showing complex cognitive abilities in invertebrates.
Verifying that the selected option accounts for the passage's main argument ensures it is the main idea.

Key Concept

Distinguishing Main Ideas from Supporting Details
Estimated Time:1m 30s
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Distinguishing Main Ideas from Supporting Details

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