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Earth's Magnetic Field

The magnetic field is like a bar magnet inside Earth; the magnetic field can flip.

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No Need for GPS

No Need for GPS

Credit: Cliff Cooper
Source: http://www.flickr.com/photos/44964483@N00/158356631
License: CC BY-NC 3.0

Animals don’t have GPS or even maps and compasses. But animals like Mexican Free-Tailed Bats migrate hundreds or thousands of miles every year. Many of these travelers use internal compasses as their guides.

Amazing But True!

Credit: T. R. Shankar Raman
Source: http://en.wikipedia.org/wiki/File:Wbeest_Mara.jpg
License: CC BY-NC 3.0

Wildebeest in the Masai Mara, Kenya during the Great Migration [Figure2]

  • Over 1.5 million wildebeest in East Africa endure an annual long migration, called the Great Migration. The migration patterns are due to changes in season which impact grass growth. The Great Migration is most known for the northwest migration at the end of the rainy season around May or June. 
  • Arctic Terns fly from their breeding grounds in the Arctic to Antarctica each year.
  • Salmon find their way thousands of miles back to where they spawned.
  • Navigation could be by the sun, landmarks, the moon and stars, scent, wind direction, or magnetic field.
  • Magnetoreception is the ability to detect magnetic fields and use them for navigation.
  • Magnetite, the strongest naturally occurring magnetic detector, has been found in some animal brains.
  • Cryptochrome is a protein found in bird retinas that may assist with navigation.

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With the link below, learn more about animal migration. Then answer the following questions.

  1. How did scientists test the hypothesis that birds navigated using the sun, moon and stars?
  2. How did scientists test the idea that trout could migrate using the magnetic field?
  3. What are “compass cells”?
  4. How might cryptochrome help birds find their way?
  5. How do humans use the magnetic field for navigation?

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Image Attributions

  1. [1]^ Credit: Cliff Cooper; Source: http://www.flickr.com/photos/44964483@N00/158356631; License: CC BY-NC 3.0
  2. [2]^ Credit: T. R. Shankar Raman; Source: http://en.wikipedia.org/wiki/File:Wbeest_Mara.jpg; License: CC BY-NC 3.0

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