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Young World
WORLD OF SCIENCE
Shark truths
DR. T.V. PADMA
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Did you know that sharks have been around even before dinosaurs?
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Sharks belong to a special category of fish called elasmobranchs. This includes skates, rays, chimeras and their relatives as well. Elasmobranchs have skeletons made of cartilage, instead of the hard, calcified bone that gives our mammalian bodies structure. Pull on your ears — see how they are soft and pliable? Our ears have cartilage. Our noses have cartilage, too. Cartilage gives shape, but it’s softer than bone. Sharks aren’t bony fish.
Another outward difference between most “fish” we can think of and “sharks” is that sharks appear to lack scales. Actually, sharks do have tiny structures on their skin called “placoid” scales or “dermal denticles”, which help to reduce friction as they swim through the water.
Characteristics
Are sharks shark-sighted — oh, I mean, sharp-sighted? Scientists think they probably have good long-range vision.
They also have excellent hearing, although, unlike humans, their ears are located inside their heads, instead of outside. In addition to their ears, they have a special organ called the “lateral line” which is a fish characteristic. The lateral line helps “hear” vibrations under water.
And what about those terrible teeth? They’re actually rather terrific teeth — sharks regrow their teeth many times in their lives. The teeth are layered, waiting to sprout up and replace any that fall or break off.
Sharks have been around for hundreds of millions of years — the ancestors of modern sharks were swimming about 400 million years ago. That makes them older than dinosaurs.
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