The oceans cover 75% of the world's surface and contain 97% of its water; 90% of the seas lie beyond the shallow continental margins, and most are deeper than 2km. With the advent of modern science we have been able to discover what some of the deep ocean is like but there is still a vast area that remains unexplored. One thing we do know is that life at these depths is dominated by animals, not plants, since light cannot reach these depths.
The forces of evolution have ensured that life has reached even the deepest tracts of the ocean. Unusual, and to our eyes, ugly and bizarre animals have developed. Fish, echinoderms, crustaceans and molluscs are represented in the depths and since no light penetrates this far, many animals have forsaken eyes and have developed long feelers instead. Some have even developed systems for producing their own light - a process termed bioluminescence. This light is used as a lure to attract food; the deep sea angler fish is a good example with its glowing lures hanging down over its mouth to entice other fish to become its meal.
Since food is scarce to come by in the depths, some fish have developed stomachs with a huge capacity and can eat prey that are larger than themselves, these fish are aptly named the "gulpers".
Hydrothermal vents (also known as black smokers) occur where the Earth's crust is thin and new sea floor is being formed. Along these spreading ridges, mini volcanoes appear on the sea bed which belch out sulphur through chimneys up to 30m high into the surrounding ocean. They also cause a local increase in temperature by spewing...
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