Sharks 101 | National Geographic

(ominous music) - They glide through the water with unmistakable grace, remnants of an ancient past, they dip and rise from the ocean's murky depths to its sun-drenched shallows, eliciting fear and awe like no other creature. at sea. The largest living fish in the world is a shark. Of the estimated 34,000 species of fish, the largest are whale

sharks

. These gentle giants typically grow to about 40 feet long and weigh approximately 15 tons. Their mouths alone can measure four feet wide. However, the gigantic whale shark pales in comparison to the largest fish that ever lived, the megalodon. It is believed that the prehistoric shark, which dates back more than 20 million years, could reach 80 feet long and weigh around 70 tons.

Unlike the whale shark, the megalodon was carnivorous, consuming any creature that could fit in its nearly 10-foot-wide mouth. Over the course of their lives, some shark species can lose more than 30,000 teeth. Unlike humans, who are born with a set number of teeth in their jaws,

sharks

have a seemingly unlimited supply. They can grow, lose, and replace their teeth as needed. Additionally, most sharks have several rows of teeth in their jaws. The jaws of a great white shark, the largest predatory fish in the sea, can contain up to seven rows containing up to 300 teeth at any point.

Most sharks, while hunting their prey, end up losing their individual teeth. However, the cookie cutter shark loses and replaces the teeth in its lower jaw all at once. Sharks are made for speed. The fastest known shark, the mako shark, can reach speeds of up to 46 miles per hour. This speed is largely due to the hydrodynamic design of its body. Many sharks have torpedo-shaped heads that allow them to pass through the water with little resistance. Additionally, the shark's skin is covered with flat, V-shaped scales called dermal denticles. The denticles help water flow smoothly over the skin, which reduces friction and helps sharks swim quickly and silently.

Sharks also have skeletons made of cartilage instead of bone. Cartilage is a much lighter material than bone, so sharks have less weight to carry. Sharks can lay eggs or have live babies. Laying sharks only lay a few large eggs. They can come in various forms, such as bags called mermaid purses or corkscrews. These eggs act as external wombs in which shark embryos complete their development. However, most sharks give birth to live young. Called hatchlings, the young of most living species gestate for about a year. Some even begin practicing their predation skills while in the womb. Before being born, bull shark pups compete with their siblings.

In fact, the strongest cub in each of the two wombs devours its weaker brothers and sisters. Some sharks are at risk of extinction. An estimated 100 million sharks are killed worldwide each year, largely for the shark fin trade. Sharks are caught and have their dorsal fins removed and sold at high prices, mainly in Asia. In traditional Chinese culture, serving and eating shark fin is a sign of status and wealth. Due to the high demand and value of shark fins, some shark populations have plummeted by up to 70%, causing a domino effect in ecosystems and endangering at least 74 shark species.

However, steps are being taken to protect sharks and several countries and jurisdictions are cracking down on unsustainable shark fishing. In China, shark fin soup is no longer allowed to be served at government banquets. A measure hailed by shark conservationists. Through continued inter

national

conservation efforts, the loss of sharks can be slowed, allowing the creatures in all their power and grace to survive for many generations to come.