Living on Earth’s Cynthia Graber reports on a study that shows how the last great ice age may have ended when multi-celled organisms evolved into being.
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GRABER: Hundreds of millions of years ago, there were times when the earth was covered in ice from the polar caps all the way to the tropics. But about 500 million years ago, these extreme ice ages ceased, and glaciers have yet to reach tropical regions again. Now some scientists in California believe they know why.
Climate scientist Andy Ridgwell and his colleagues at UC Riverside and Lawrence Livermore National Lab discovered that the extreme ice ages stopped just about the time life in the ocean began to develop from single-celled organisms to more complex, multi-celled creatures. One of these tiny creatures began to manufacture a shell from a substance calcium carbonate. Turns out that when calcium carbonate dissolves in ocean waters it makes the water less acidic. It also stabilizes the water, preventing wild swings in pH. And since the pH of ocean water regulates the amount of carbon dioxide in the atmosphere, a more stable ocean pH means a more stable supply of heat-trapping carbon dioxide.
No one knows exactly why these tiny creatures evolved shells. It might have been to support a larger body, or to protect themselves from predators. But by doing so, these sea animals changed the chemistry of the ocean, and stabilized the carbon dioxide enough in the atmosphere to help make earth habitable for life, as we know it.
That’s this week’s Note on Emerging Science, I’m Cynthia Graber.
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