1000 Facts Sharks

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Submit Feedback. Thank you for your feedback. Introduction Natural history Distribution Physical features Reproduction and territoriality Predators and prey Paleontology Extinction. Written By: John P. See Article History. Alternative Titles: Carcharocles megalodon, Carcharodon megalodon. Facts Matter.

50 Shocking Facts about Sharks

Start Your Free Trial Today. Load Next Page. More About. Because of this, if someone rubbed the skin from the head towards the tail, it would feel very smooth. In the opposite direction it feels very rough like sandpaper. As the shark grows, the placoid scales do not increase in size. Instead the shark grows more scales. Do sharks sleep? It was once believed that all sharks had to swim constantly in order to breathe and could not sleep for more than a few minutes at a time.

Oxygen-rich water flows through the gills during movement allowing the shark to breathe. While some species of sharks do need to swim constantly, this is not true for all sharks.

10 Amazing MEGALODON Facts

Some sharks such as the nurse shark have spiracles that force water across their gills allowing for stationary rest. Do sharks have good eyesight? Sharks have the ability to open and close the pupil in response to differing light situations similar to humans while most fish do not possess this ability.

Scientific Name: Elasmobranchii

In addition, sharks, similar to cats, have a mirror-like layer in the back of the eye referred to as the tapetum lucidum. Although it was once thought that sharks had very poor vision, we now know that sharks have sharp vision. Research has shown that sharks may be more than 10x as sensitive to light as humans.

Scientists also believe that sharks may be far-sighted, able to see better at distance rather than close-up, due to the structure of the eye. Vision varies among species of sharks due to differences in the size, focusing ability, and strength of the eyes.

Natural history

Can sharks hear? Sharks have an excellent sense of hearing with ears located inside their heads on both sides rather than external ears like humans. Sharks can hear best at frequencies below 1, Hertz which is the range of most natural aquatic sounds. This sense of hearing helps shark locate potential prey swimming and splashing in the water. Sharks also use their lateral line system to pick up vibrations and sounds. Why do sharks have so many teeth?

Sharks have lots of teeth arranged in layers so if any break off, new sharp teeth can immediately take their place. Sharks can shed thousands of teeth during their life, this is why sharks teeth can be found washed onto beaches. Why are most sharks a lighter color underneath? The upper portion of the shark is dark in color to make it difficult to see the shark from above against the dark ocean water.

Sharks have a lateral line system along their sides which detects water movements. This helps the shark find prey and navigate around other objects at night or when water visibility is poor.

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Pressure waves in the ocean water around the shark vibrate this liquid. Sharks need to keep water moving over their gills to receive necessary oxygen. Not all sharks need to move constantly, though. Sharks that do need to swim constantly have active and restful periods rather than undergoing deep sleep like we do. Some shark species are oviparous, meaning they lay eggs. Others are viviparous and give birth to live young.

Within these live-bearing species, some have a placenta just like human babies do, and others do not. In those cases, the shark embryos get their nutrition from a yolk sac or unfertilized egg capsules filled with yolk. With the sand tiger shark, things are pretty competitive. The two largest embryos consume the other embryos of the litter. While nobody seems to know for certain, it has been estimated that the whale shark, the largest shark species, can live up to years, and many of the smaller sharks can live between 20 and 30 years. Bad publicity around a few shark species has doomed sharks in general to the misconception that they are vicious man-eaters.

In fact, only 10 out of all the shark species are considered dangerous to humans. All sharks should be treated with respect, though, as they are predators, often with sharp teeth that could inflict wounds especially if the shark is provoked or feels threatened.