Creatures at the Bottom of the Sea
Giant Tube Worms (Riftia pachyptila)
The picture to the left depicts a Giant Tube Worm. This deep sea organism lives at the bottom of the sea and thrives even without sunlight. Why is this, you ask? Well, that's because the Giant Tube Worm (along with plants and algae) is part of a group of organisms called autotrophs (which means they produce their own food). Animals (including humans) generally tend to be heterotrophs, an organism requiring input from other organisms for its main source of food. Autotrophs that perform a process known as chemosynthesis (like the aforementioned Giant Tube Worms) do not use energy from the sun to produce food. Instead, they make food using energy from chemical reactions, often combining hydrogen sulfide or methane with oxygen. However, For this reason, tube worms are partially dependent on sunlight as an energy source, since they use free oxygen, which has been liberated by photosynthesis in water layers far above, to obtain nutrients.
Organisms that use chemosynthesis live in extreme environments, where the toxic chemicals needed for oxidation are found. For example, bacteria living in active volcanoes oxidize sulfur to produce their own food. At Yellowstone National Park in the U.S. states of Wyoming, Idaho, and Montana, bacteria capable of chemosynthesis have been found in hot springs.