in any shape or form,HedgeThey have existed for about 400 million years.
Even before dinosaurs roamed the earth, sharks hunted in our oceans and even in some rivers and lakes. Sharks are such good survivors that they have hardly had to evolve in the last 150 million years.
There are around 360 different species of sharks, divided into 30 families. These different families of sharks vary greatly in their appearance, life, and diet. Sharks have different shapes, sizes, colors, fins, teeth, habitats, diet, personality, method of reproduction and other characteristics.
Some species of sharks are very rare (like the great white shark and the trout shark) and others are fairly common (like the doge shark and the bull shark). Sharks belong to the group of cartilaginous fish, the 'Elasmobranchii', which includes sharks, rays and rays.
Sharks are among the world's most misunderstood predators and will never attack humans unless intimidated. These ancient predators fascinate people everywhere.
Unlike bony fish, sharks have no bones: their skeleton is made of cartilage, a tough, fibrous substance that's not as hard as bone. Sharks have a streamlined body shape that glides smoothly through the water and contains five to seven gill slits that they use to breathe.
Some bottom-dwelling sharks, like the Angel Shark, have flat bodies that allow them to hide in the sand on the sea floor. Some sharks have an elongated body shape like cookiecutter sharks and wobbegongs. Sawsharks have elongated snouts, threshers have enormously elongated upper caudal fins they use to stun prey, and hammerheads have exceptionally broad heads. The goblin shark has a large, spiny bulge on its head, its purpose unknown.
Sharks have a shell of dermal denticles (small growths covering the skin) to protect their skin from damage and parasites and to improve fluid dynamics. Sharks have the strongest jaws in the world. Unlike most animals, both the upper and lower jaws of the shark move.
A shark bites first with its lower jaw, then with its upper jaw. It moves its head from side to side to rip off a chunk of flesh, which it swallows whole.
Each species of shark has a differently shaped tooth depending on its diet. Since shark teeth are interchangeable, they can grow and use more than 20,000 teeth in their lifetime.
Sharks include species from the tiny pygmy shark (Euprotomicrus bispinatus), a deep-sea species just 22 centimeters long, to the whale shark (Rhincodon typus), the largest fish, reaching about 12 meters (39.36 feet) in length. . ) and, like large whales, feeds exclusively on plankton by filter feeding (filtering suspended matter and food particles from the water). In general, sharks swim or cruise at an average speed of 8 kilometers per hour (5 miles per hour), but when feeding or charging, the average shark can reach speeds in excess of 19 kilometers per hour (12 miles per hour).
Sharks usually eat alone. However, sometimes a feeding shark attracts others. They swim as fast as they can and everyone tries to get a piece of the prey. Sharks will brutally bite anything in their path, even each other. Almost all sharks are carnivores or carnivores. Sharks feed on fish and marine mammals (such asdolphinsjseals) and even dams liketurtlesand seagulls.
Sharks even eat other sharks. for example aTigerhaicould eat a bull shark, a bull shark could eat youSchwarzspitzenhaiand a blacktip might eat a dogfish. It's a bit like a shark eat shark life under the waves.
Not all are wild carnivores. Some are quite harmless. Oddly enough, the most harmless sharks tend to be the largest sharks. The basking sharkWalhaiand the Megamouth Sharks fit that description. These huge sharks eat plankton, a small shrimp-like creature found in the ocean. They swim forward with their mouths wide open. The "gill rakes" at the back of the throat filter the small meal out of the water and are called filter feeding (as mentioned above).
Male and female sharks can be easily identified. Male sharks have modified pelvic fins that have become a pair of brooches. The name is a bit misleading as they are not designed to hold the female but serve as the penis of mammals. During mating, the more flexible sharks coil around each other, with the male usually coiling around the female. In less flexible sharks, males and females swim side by side while the male inserts a hook into the female's oviduct (the passageway for the ovaries on the outside of the body).
Female sharks in many of the larger species have bite marks that appear to be the result of a male grabbing them to hold position during mating. Bite marks can also result from courtship behavior: the male may bite the female to show interest. In some species, the females have evolved thicker skin to withstand these bites.
Sharks have a different reproductive strategy than most fish. Sharks do not mass produce, instead having between 1 and 100 pups at a time. Blue sharks have been reported to have had 135 pups, while some sharks only have two. No species of shark is known to provide postnatal parental protection to its young, but females release a hormone into their blood during the breeding season that appears to prevent them from feeding on their young.
There are three ways a shark pup can be born:
Pair of doors– Some sharks lay eggs. In most of these species, the developing embryo is protected by a leathery egg covering. Sometimes these sheaths curl into crevices to protect them. Sometimes the egg cartons wash up on the beach and are known as the "mermaid's bag". Sharks that give birth this way include: Horn Shark, Catshark, Port Jackson Shark, and Swellshark.
liveliness– These sharks maintain a placental attachment with developing pups that is more similar to mammalian pregnancy than other fish. The young are born alive and fully functional. Hammerheads, requiem sharks like bull and tiger sharks, basking and dogfish all fall into this category. The dog shark has the longest known gestation period of any shark at 18 to 24 months. Basking and frilled sharks are likely to have even longer gestation periods.
Ovovivi pairs– This is the most common method used by sharks. The young feed on the yolk and fluids secreted by glands in the walls of the fallopian tube. The eggs hatch in the oviduct, and the young continue to be nourished by the remaining portions of the yolk and oviduct fluid. As with viviparity, the young are born alive and fully functional. The mostovoviviparous Come onThey give birth in sheltered areas, including bays, estuaries, and shallow reefs. They choose such areas for protection from predators (mainly other sharks) and abundance of food.
Shark tails (tail fins) vary greatly between species and are tailored to the sharks' way of life. Its tail provides thrust, so speed and acceleration depend on the shape of the tail. Different tail shapes have evolved in sharks adapted to different environments. The tiger shark's tail has a large upper lobe that provides maximum power for slow cruising or sudden bursts of speed.
The tiger shark has a varied diet and therefore needs to be able to twist and turn easily in the water when hunting, while the porbeagle shark, which preys on schooling fish such as mackerel and herring, has a large underlobe to ensure increased speed to help it, to keep up with its swift prey
Some tail adjustments serve purposes other than providing thrust. The Cookiecutter Shark has a tail with similarly shaped broad lower and upper lobes that luminesce and can help attract prey to the shark. The thresher shark continues to feedpezand squid, thought to form flocks, then stun them with their powerful, elongated upper lobe.
protection of sharks
Most shark fisheries around the world are poorly monitored or managed. With the increasing demand for shark products, the pressure on the fisheries increases. Populations decline and collapse because sharks are long-lived apex predators with comparatively small populations, making it difficult for them to breed fast enough to maintain population levels. Significant declines in shark populations have been recorded in recent years: some species have declined by more than 90% in the last 20-30 years, and a 70% decline is not uncommon.
Many governments and the UN have recognized the need to manage shark fisheries, but little progress has been made due to shark fisheries' low economic value, low production levels and poor public image. Many other threats to sharks include habitat modification, damage and loss of coastal developments, pollution, and the impact of fishing on the seabed and prey species.
Related post–behavior of sharks
More fascinating animals to learn about
Galapagos Hammerhead Shark
Blacktip Reef Shark