BOX 3.3 Bio-magnetism


For centuries, we have used the magnetic properties of lodestone or magnetite to navigate our way around the world. We are not the only animals to take advantage of the directional information that the Earth's magnetic field provides. Researchers have discovered that some kinds of bacteria use the magnetic field to determine which way is up. These bacteria form linear chains of internal magnetite crystals to detect the direction of the Earth's magnetic field. Scientists have discovered that organisms started crystallizing magnetite nearly 2 billion years ago. Tiny magnetite crystals have been found in brains of larger animals, such as pigeons, honey bees, and sea turtles, whose abilities to find their way home has been a fascinating puzzle for years. Magnetite grains have also been found in human brains, although we apparently do not use our internally-grown magnetite to find our way home


Questions

What sorts of experiments could you devise to test whether an animal uses the Earth's magnetic field to navigate? What other tools do we use to locate ourselves besides a compass? Amazing stories tell of lost pets traveling hundreds of miles to return home. What possible tools do they use?


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