The Hidden Clues in Whale Legs

Lexile: 970 | Grade: 7

Passage

Whales are known for being massive, smooth-bodied sea creatures, gliding through oceans with powerful tails and flippers. But did you know that whales once walked on land?

Scientists have discovered fossils that show whales had tiny back legs millions of years ago. These legs weren’t for swimming—they were for walking.

The theory is that whales evolved from land animals that slowly returned to the water over millions of years. As they adapted to aquatic life, their legs became smaller and eventually vanished on the outside. However, deep inside the whale’s body, tiny leg bones still exist today.

These leftover bones are called vestigial structures—parts of the body that no longer serve a clear purpose but tell a story about the past.

Studying vestigial structures helps scientists understand how animals change over time. In the case of whales, these hidden clues reveal a long journey from land to sea.

So next time you see a whale, remember—it carries history in its bones.

Questions

Q1: What is the main idea of this passage?

  • A. Whales are the largest animals in the sea.
  • B. Whale fossils show that whales once had legs and lived on land.
  • C. Scientists are unsure how whales move through water.
  • D. Whales use their tails and flippers for swimming.

Q2: What is the function of the last sentence: 'So next time you see a whale, remember—it carries history in its bones.'?

  • A. It introduces a new idea about whale behavior.
  • B. It explains the scientific name for whale bones.
  • C. It adds a dramatic conclusion to emphasize the passage’s main idea.
  • D. It argues that whales are smarter than we think.

Q3: What does the word 'vestigial' mean as used in paragraph 4?

  • A. Strong and powerful
  • B. Left over from the past and no longer used
  • C. Recently discovered
  • D. Easily seen from the outside

Q4: Why does the author include the detail that whales still have tiny leg bones inside their bodies?

  • A. To show that whales are poorly adapted to swimming
  • B. To prove that whales are related to sharks
  • C. To support the idea that whales evolved from land animals
  • D. To explain why whales need extra bones

Q5: Which sentence from the passage best shows the author’s purpose?

  • A. 'Whales are known for being massive, smooth-bodied sea creatures…'
  • B. 'These leftover bones are called vestigial structures…'
  • C. 'Scientists have discovered fossils that show whales had tiny back legs…'
  • D. 'So next time you see a whale, remember—it carries history in its bones.'

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Answers & Reasoning

Q1: What is the main idea of this passage?

✅ Correct Answer: B

💡 Reasoning: The passage explains that whales once had legs and lived on land, and how this is known through fossils and vestigial structures.

Q2: What is the function of the last sentence: 'So next time you see a whale, remember—it carries history in its bones.'?

✅ Correct Answer: C

💡 Reasoning: The sentence adds a reflective, memorable ending that ties back to the main idea of whales' evolutionary past.

Q3: What does the word 'vestigial' mean as used in paragraph 4?

✅ Correct Answer: B

💡 Reasoning: The passage explains that these structures no longer serve a purpose but are clues to the past.

Q4: Why does the author include the detail that whales still have tiny leg bones inside their bodies?

✅ Correct Answer: C

💡 Reasoning: This detail supports the passage’s explanation that whales once walked on land and evolved over time.

Q5: Which sentence from the passage best shows the author’s purpose?

✅ Correct Answer: C

💡 Reasoning: This sentence introduces key scientific evidence that helps explain whale evolution, aligning with the author’s informative purpose.