Well . About thirty years ago, researchers sent a deep-sea vessel to explore the ocean’s depths—about 3 kilometers down—way deep!—to the ocean floor. No one had ever explored that far down before—nobody expected there to be any life down there—because of the conditions . First of all, sunlight doesn’t reach that far down, so it’s totally dark . There couldn’t be any plant or animal life—since there’s no sunlight—no source of energy to make food. If there was any life at all, it’d just be some bacteria breaking down any dead materials that might’ve fallen to the bottom of the ocean . Ann? And what about the water pressure? Didn’t we talk before about how, the deeper down into the ocean you go, the greater the pressure? Excellent point! And not only the extreme pressure, but also the extreme temperature of the water around these vents—if the lack of sunlight didn’t rule out the existence of a biological community down there, then these factors certainly would… Or so they thought . So you’re telling us they did find organisms that could live under those conditions?
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They did indeed—something like three hundred different species!
But—but—how could that be? I mean—without sunlight—no energy—no, no— What they discovered was that microorganisms—bacteria—had taken over both functions of the biological community—the recycling of waste materials, and the production of energy; they were the energy source . You see … it turns out that certain microorganisms are chemosynthetic; they don’t need sunlight because they take their energy from chemical reactions . So, as I said, unlike green plants, which are photosynthetic, and get their energy from sunlight, these bacteria that they found at the ocean floor—these are chemosynthetic, which means that they get their energy from chemical reactions . How does this work? As we said, these hydrothermal vents are releasing into the ocean depths this intensely hot water—and… here’s the thing: this hot water contains a chemical called hydrogen sulfide, and also a gas—carbon dioxide. Now, these bacteria actually combine the hydrogen sulfide with the carbon dioxide, and this chemical reaction is what produces organic material, which is the food for larger organisms . The researchers had never seen anything like it before! Wow! So just add a chemical to a gas, and—bingo!—you’ve got a food supply?! Not just that—what was even more surprising were all the large organisms that lived down there . The most distinctive of these was something called the tube worm . Here, let me show you a picture … The “tube” of the tube worm is really, really long—they can be up to one and a half meters long. And these “tubes” are attached to the ocean floor. Pretty weird-looking, huh? And another thing—the tube worm has no mouth or digestive organs! So, you’re asking, how does it eat? Well, they have these special organs that collect the hydrogen sulfide and carbon dioxide, and then transfer it to another organ … where billions of bacteria live . These bacteria that live inside the tube worms: the tube worms provide them with hydrogen sulfide and carbon dioxide, and the bacteria …well, the bacteria kind of “feed” the tube worms through chemosynthesis—remember? That chemical reaction I described earlier …
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