Do sharks belong to fish and how do sharks be classified?

Sharks belong to the genus of fishes and belong to the phylum Chordates, Subphylum Vertebrates.

There are 8 orders and 25 families with about 250 300 species of cartilaginous fishes, plategill subclasses and sharks.

Sharks are all born in the sea, and a few species can enter freshwater, and they are a type of medium-to-large marine fish that swim fast.

The shark is an ancient fish, and its fossils appear hundreds of millions of years before the dinosaurs, judging from the fragments of shark teeth and spines that have been excavated. In this long history, some species of sharks have disappeared through natural selection, and there are still some vulnerabilities of species in the more than 300 species that are still alive today, such as slow growth, late sexual maturity, and reproduction is also once every two years, and the reproduction rate is also extremely low.

The endoskeleton of the shark is composed entirely of cartilage, often calcified, but without any true bone tissue, the exoskeleton is not very developed or degenerate, the body is often covered with skin teeth (qualitative scales), the teeth are diverse, and there is hard muscle, but the membranous bone never exists, and the brain is seamless.

The body is spindle-shaped, with cleft gills on both sides of the head, but resembles a common fish. With a few exceptions, the typical shark** is hard, dull gray in color, with tooth-like scales that make ** appear rough. tail strong and powerful, asymmetrical, upturned; Fins are pointed; The snout is appointed, protruding, with a crescent-shaped mouth and a triangle under the snout.

Fang. Sharks have no swim bladder and need to swim constantly to avoid sinking to the bottom.

Shark teeth are made up of dentin, osteodontic, and enamel-like textures.

It evolved from shield scales. That is, the teeth of sharks are actually their scales, which can grow indefinitely.

Sharks have oviparous and ovoviviparous.

Two ways of reproduction.

Sharks are fish.

Sharks are fish.

Sharks are fish, a type of fish of the phylum Vertebrates, the class Chontilagina, that live in the ocean, are fish in the ocean, breathe with gills and swim in the water with fins. The body of the shark is long spindle-shaped, the pectoral fins are normal, there are gills on both sides of the head, and most sharks have hard, dark gray teeth, and many shark tooth patterns.

Sharks reproduce mainly through three methods: oviparous, ovoviviparous, and viviparous. When the body length increases to a certain length, the rate of growth begins to slow down, while the weight gains rapidly. Data show that freshwater sharks generally grow at an average rate of more than 15 grams per day during the suitable growth time between June and January.

Freshwater sharks that have been raised for 2 years can grow to more than 2 kilograms.

1. Great white shark.

Great white sharks are relatively large in size. They are very aggressive and have teeth that are about 10 centimeters long. Their tails are crescent-shaped and more distinctive.

2. Red-tailed sharks: The origin of this shark is in Thailand, although their size is not particularly large, but their personality is more irritable, and they have a strong sense of territory.

3. Steller's shark.

Steller sharks are an ornamental shark species that can be kept in tanks. Their body length in adulthood is 30-40 cm, and they are still relatively small. Their feeding habits are relatively mixed, and they do not have too high requirements for oxygen content in the water, and their adaptability is relatively good.

4. Whale sharks. It is the largest shark species and the largest fish in the world. In adulthood, they can even reach a body length of 20 meters.

Key Value:

1. Shark watching.

Some large oceanariums at home and abroad.

Aquariums have specially opened shark aquariums, raising more than 10 kinds of sharks with character training and ornamental value, such as striped bamboo shark (also known as spotted bamboo dog twisting) and leopard shark (also known as big-tailed tiger stripes), and the keepers dive into the pool (box) to feed the sharks or dance with the sharks to show visitors the mysterious shark world.

2. Maintainer of marine ecological balance.

Sharks are almost exclusively carnivorous species, with only a few species such as whale sharks, state hail and basking sharks known as plankton.

for food. Carnivorous sharks have well-developed two collars, strong contractile muscles in the lower collar, and sharp teeth, so they have a strong bite and can eat mollusks.

Crustaceans, large fish and marine mammals.

Worse still, they will attack small boats and devour people. In the marine ecosystem, sharks are the uppermost part of the biological chain and play an important role in maintaining ecological balance.

3. Provide materials for industry.

Sharks have well-developed livers with 2-3 lobes, and their weight accounts for 15%-20% of their total body weight. The oil content in the liver is as high as 63%, and this oil does not freeze at -50. In addition, shark skin is processed to make high-quality leather.

The above content reference: Encyclopedia - Shark.