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Airdate: Apr 07, 2000
Scientist: Vincent Cassone

Biological Clocks: Compass

Biological Clocks:  Compass
In some animals, the biological clock that regulates internal processes serves as a compass as well as a timekeeper.

Transcript:
As you watch Canada geese fly south for the winter, or head back up north as the weather warms, you might pause to admire their perfect "V" formation. You might also marvel that they all agree on when it's time to travel. And how do they know exactly where they're going, and how to get there? Well, it's all thanks to their biological clocks. I'm Jim Metzner, and this is the Pulse of the Planet, presented by DuPont. Virtually all plants and animals on earth have a kind of biological clock, a part of the organism that regulates internal processes using environmental cues, such as sunlight. In humans, the biological clock helps determine when we eat and sleep. But in some creatures, the clock also serves as a compass. Vince Cassone is a professor of biology at Texas A & M University.
"Many migrating animals will actually navigate at least in part by using their biological clock as a compass, predicting where the sun should be and a recognition of where it is right now."
This combination of clock and compass can work in remarkably complex ways. For example, a female sea turtle comes back to the same place to lay her eggs, at a specific time each year and at a certain point in her reproductive life.
"And all three of those aspects are regulated by the circadian clock, or approximately a day clock, by a recognition of the tides and by their recognition of the time of year. So the biological clock is employed by a creature like the sea turtle at all levels. Where you are, what time of day you are, what tide you're coming up on and what time of year you need to lay your eggs."
Pulse of the Planet is presented by DuPont, bringing you the miracle of science, with additional support provided by the National Science Foundation. I'm Jim Metzner.