Sharks have a skeleton of cartilage and belong to the class of cartilaginous fish (Chondrichthyes). This makes them fast and fast when swimming. The largest shark that exists is the whale shark (Rhincodon typus), which reaches 18 meters in length and weighs 20,000 kilograms, and one of the smallest is the shark dwarf lantern (Etmopterus perryi) of 20 centimeters in length.
There are approximately 450 different shark species, and more species are still found today.Physical characteristics
Sharks have thick fins without spines, which are very firm. The fins of the sharks are: dorsal fin, primary dorsal fin, pectoral fin, pelvic fin, tail fin and anal fin.
The eyes of the sharks are adapted to be able to see with little luminosity, and their pupils can expand and contract. Most sharks see black and white.
Sharks have an extraordinary sense of smell, so they can detect their prey miles away, they also have internal ears, with which they can hear very low frequencies, which helps them to hear fish miles away.
Sharks have gills and with them they extract oxygen from water to be able to breathe. Something surprising is that the sharks if they stop moving are drowning, since they need to be in constant movement so that enough water passes through their gills and they can breathe normally.
Their teeth are large disposable weapons in the shape of triangles, which help them to tear flesh. Sharks do not have a tongue, but at the base of the mouth they have a cartilage.
Sharks have about 3,000 teeth, and their teeth are attached to the skin and not the jaw, this allows them to be disposable, since sharks lose many teeth throughout their lives. A shark can have about 50,000 teeth in its entire life.
The color of the sharks depends on the spice that is, they can be of smooth colors, with polka dots, with stripes, etc, equally the size and the weight will depend on the species.
Sharks inhabit all the oceans of the world, and depending on the temperature of the water, make large migrations in search of temperate waters.
Sharks are carnivorous and feed on small fish, squid, dolphins, tuna, turtles, marine mammals, such as seals, sea lions, rays, among others, also eat plankton, which trap filtering water. In the case of the white shark (Squalus carcharias), it can also eat other species of smaller sharks. Some shark species make large migrations in search of food.
At the time of attack, a few species of sharks do so by ambush, swim near the surface, and at dawn or dusk, is where they attack their prey.
The sexual maturity of the sharks will depend on the species, some reach it at 8 years and others do not reach it until they are 18 years old.
Sharks reproduce by internal fertilization. In most shark species females breed their eggs inside the belly and give birth to their already formed offspring, which are abandoned once they are born. But some shark species such as Port Jackson (Heterodontus portusjacksoni) or horned suño (Heterodontus francisci) lay their eggs in bags, called siren bags.
Sharks have different tails, depending on the species, and the tail is the extension of your spine, and depending on the kind of tail they have, this tells us if they are fast or slow swimmers. The fastest sharks reach 32 km / h.
Some kinds of sharks are: whale shark, zebra shark, tiger shark, dwarf shark, bull shark, white shark, carpet shark, gorget shark, cigar shark, among others.
Sharks live between 20 and 30 years, although the whale shark can live to 100 years.
The most dangerous sharks are the great white shark, the bull shark (Carcharhinus leucas) and the tiger shark (Galeocerdo cuvier), these are responsible for almost 100% of the attacks on humans.
The most feared of all is the white shark, with a length of about 6 meters, this fearsome shark hunts seals, dolphins and even other species of sharks. They are very aggressive and strong.
Sharks do not sleep, they just rest on the bottom of the sea, and while they rest they are watching everything that happens around them. Some rest half of the brain and then the other half.
Although sharks are attracted to the smell of blood, what attracts them most is the smell of fish gut. They have such a good sense of smell that they are able to detect a drop of blood in a hundred liters of water, and this is why it is their main weapon when it comes to hunting. Once he detects where the smell comes from, he swims there at full speed.
Some sharks shine because they use bioluminescence, and this allows them to shine to confuse their prey.
The only predator of sharks is the orca, who has even been seen attacking the fearsome white shark.
It is estimated that around 100 thousand sharks are killed each year in the world, some for commercial use and others for sport fishing.