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Where does a breath-hold diver keep the oxygen?

A breath-hold diver carries oxygen in more places than the lungs. Blood hemoglobin and muscle myoglobin also hold oxygen, while changes in heart rate and blood flow affect how those stores are used. The oxygen supply remains finite throughout the dive.

3–5 min

Questions you could explore

  • How is storing more oxygen different from using it more slowly?

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Health and the body

How does daylight set the body’s clock?

Feeling sleepy at night involves more than counting the hours since you woke up. Internal daily rhythms respond to outside cues, with light helping coordinate the body's sense of time.

3–5 min

How does daylight set the body’s clock?

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4–5 min

How does a vaccine give the immune system a memory?

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Health and the body

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2–3 min

Why won’t an antibiotic treat a viral cold?

Health and the body2–3 minThe word infection covers illnesses caused by very different organisms. An antibiotic that helps against certain bacteria has no matching target in the viruses that cause a cold.

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