Whales are mammals and the largest animals in the ocean. Some whales are very big, the largest can reach more than 30 meters, and the smallest is more than 5 meters. At present, the largest known whale weighs about10.6 thousand kg, and the smallest is 2000 kg. A whale weighing nearly 40,000 kilograms and about 1.7 meters long was found in China. Whales look like fish and are spindle-shaped. Big head, small eyes and completely degenerated auricle. The neck is not obvious. The forelimbs are fin-shaped and the hind limbs are completely degenerated; Most species have fins on their backs; The tail is a horizontal fin, which is the main motor organ. Toothed or toothless. One or two nostrils, growing on the top of the head. There is no hair all over the body (many species only have some hair on their mouths). There is a thick layer of fat under the skin, which can keep warm and reduce the proportion of the body. Breathe with your lungs, then inhale on the surface and dive into the water. You can dive 10 ~ 45 minutes. They usually feed on zooplankton, mollusks and fish. Viviparous, usually each fetus gives birth to a child and feeds the calf with milk. But many people classify them as fish. In fact, they are not fish, but mammals. Distributed in the oceans of the world. The reproductive ability of whales is very poor, and it takes an average of two years to give birth to a calf. Due to the killing of human beings and the pollution of the marine environment, the number of whales has decreased sharply. For example, the largest blue whale among cetaceans, which killed nearly 360,000 in the 20th century, is now less than 50! Whales are distributed in all the oceans in the world. It is an aquatic mammal that breathes with its lungs. Its species are divided into two types: fin whales, toothless, bearded whales and two nostrils, fin whales, blue whales, humpback whales and gray whales, which are relatively mild; Toothed whales have teeth, no baleen whales, and usually have one or two nostrils. There are sperm whales, narwhals, killer whales and other species, which are more fierce. Most of the oxygen in the ocean and 60% of the oxygen in the atmosphere are made by phytoplankton. Baleen whales can destroy zooplankton, the number one enemy of phytoplankton. In addition, toothed whales also help to maintain the ecological balance of fish. Toothed whales are large mollusks that feed on fish. Therefore, without whales in the world, human beings will perish. Cetaceans are characterized by constant body temperature, about 35.4℃. Bare skin, no body hair, only a few bristles on the nose and mouth, no sweat glands and sebaceous glands. The fat under the skin is very thick, which can keep the body temperature and reduce the proportion of the body in water. The skull is developed, but the skull is smaller, the face is larger, the frontal bone and maxilla are obviously prolonged, forming a long snout. The neck is not obvious, the cervical vertebra is healed, and the head is directly connected with the trunk. The forelimbs are fin-shaped, the toes are not separated, there are no claws, and the elbow and wrist joints cannot move flexibly, which is suitable for swimming in the water. The hind limbs are degenerated, but there are still pelvic and femoral residues, and residual bone fragments can be seen. The tail degenerates into fins, and the skin at the end expands horizontally from left to right, forming a pair of large tail leaves without bone support. The spine gradually tapers in the long and narrow caudal trunk and finally disappears before entering the caudal fin. Unlike fish, the caudal fin can swing up and down and is the main organ for swimming. Some species also have dorsal fins to balance their bodies. Their bones have spongy tissue, and there is more fat in the body cavity, which can increase the volume of the body, reduce the proportion of the body and increase buoyancy. Iraqi whale

Their eyes are small, without lacrimal glands and transient membranes, and their eyesight is poor. There is no outer ear shell, and the external auditory canal is very thin, but the hearing is very sensitive. It can feel ultrasonic waves, find food by echolocation, contact companions or avoid enemies. There are 1-2 external nostrils, located on the top of the head, commonly known as spray holes. Generally, the closer the nostril is, the higher the degree of evolution. Breathing with lungs, there is a lung on the left and right, and there are many capillaries in it, which are elastic and can help the circulation of oxygen and adapt to the gas exchange on the water. You need to surface for air every once in a while, and you can also dive for a long time. There are 10 20 pairs of ribs. The stomach is divided into four chambers. Most kidneys are tumor-like. Male testicles are located in the abdominal cavity. Female animals give birth and breastfeed in water. The uterus has two horns and a pair of breasts, which are located at the cleavage on both sides of the reproductive fissure, and the nipples are slender. Milk is rich in calcium, phosphorus and a lot of fat. Young whales have teeth in the embryonic period, but whales' teeth are replaced by beards at birth, and toothed whales' teeth are preserved for life. A whale is a mammal that lives in water. It has the same physiological characteristics as terrestrial mammals, such as breathing with lungs and viviparous, and is equipped with some special physiological structures evolved to adapt to the aquatic environment. Under Cetacea, there are two suborders, namely blaleenwhales and toothedwhales. The grouping of these two groups is mainly determined by their different feeding patterns. The main morphological feature of the suborder baleen whales is that they have no teeth, but there are great baleen whales, which can be used to screen plankton, so they are filter feeders. The main feature of Toothed Whale suborder is that it has teeth and is predatory, and the number and arrangement of teeth will be different from the direction of predation. There are about 79 species of 13 families in the world. Although the whale has the word fish, it is actually not a fish, but a mammal. It has many characteristics very different from fish. For example, the average fish swings its tail fin left and right to move forward, while the whale swings its tail fin up and down. They use the flippers at the front end to keep balance and control the direction of force. Some whales have fins at the upper end of their backs to keep their bodies upright. Whales are social animals. They usually live in groups in the sea, but when whales breathe, they need to swim to the surface. At this time, the whale breathes through the blowhole on its head, and when it exhales, the water in the air will condense and form the familiar fountain shape. Experts can even tell the species of whales from the height, width and angle of water spray. There are many kinds of whales, which can be roughly divided into toothed whales and baleen whales. Whales have a very thick layer of fat under their skin, which is also commonly known as whale oil. It can keep whales warm and store energy for a rainy day. Because whales have many special structures in their bodies, they can breathe in the water for a long time and slow down their heartbeat. Therefore, when it sinks to the bottom of the sea, it will take a long time to surface again. In addition to the oxygen storage structure, when a certain part of the body needs a lot of blood supply, the body will also have a special function of centralized supply. At present, at least five species of whales in the world 13 are on the verge of extinction because of human hunting. In order to protect whales, the International Whaling Commission banned commercial whaling from 1986, but this ban was relaxed in 1987, allowing limited whaling for research purposes. Despite widespread opposition, some countries (especially Japan) still kill whales in large numbers in the name of "scientific research" every year. Whales occasionally surface to breathe. Its nostrils are overhead. When it comes to the surface, it will spit out a column of water. Different whales have different water columns. The water column ejected by baleen whales is high and thin, while the water column ejected by toothed whales is thick and short. Experienced people can calculate the species, size and age of whales by observing the water column. We also know that whales are not fish. The creation of the Chinese character "whale" clearly shows that the ancients thought the whale was a big fish, not to mention the word "whale". We can't blame the word-makers for their lack of biological knowledge, because cetaceans, including whales, dolphins and porpoises (smaller dolphins), are really similar to fish: their long bodies are streamlined, their tails are leaflike, their hind limbs degenerate to nothing, and only a little residue can be found inside their bodies, all of which are suitable for living in water. whale

Scientists believe that mammals and dinosaurs entered the evolutionary stage at about the same time, and they did not live well in the era when giant reptiles were rampant. Dark clouds didn't have a chance until an extinction event-it is generally believed that an asteroid hit the earth 65 million years ago-destroyed the dinosaur family. During the Tertiary period between 50 million and 65 million years ago, all mammals lived on land, and the ancestors of modern whales were no exception. For some reason, some animals running on all fours began to return to rivers and oceans in Eocene 50 million years ago. In less than 8 million years, their body shapes and living habits have undergone tremendous changes. These discoveries, especially the bucky cetaceans, have excited scientists enough, because they are a transitional type between land mammals and modern cetaceans, and once again provide beautiful evidence for evolution. However, these transitional fossils are more inclined to the whale side, either amphibious or completely adapted to marine life. There are two important questions unanswered: What is the land ancestor of cetaceans-the most primitive cetaceans that can only run but not swim? Among the existing mammals in the world, which one has the closest relationship with cetaceans? Scientists are committed to studying the evolution of whales in more detail, and different professionals have different methods. According to the characteristics of fossil teeth and ears, paleontologists tend to think that whales are closely related to the middle class animals, which are extinct ungulates that lived in the tertiary period. Molecular biologists who study the DNA characteristics of existing animals prefer hippopotamus, believing that this modern cloven-hoofed animal is a close relative of whales. On September 20th this year, Tavison published a report in the British magazine Nature, saying that his team had newly discovered two kinds of ancient whale fossils from Pakistan, which were completely terrestrial. On the second day, gingerich reported in the American magazine Science that the other two ancient whale fossils also excavated in Pakistan have developed limbs and may be amphibians. It seems that there are only a few big names in each field, and these two are probably a little competitive. It is also interesting to publish a report on the same topic in two magazines of equal status. Their new findings show that cloven-hoofed animals such as cattle, hippos, pigs, camels and giraffes are closely related to whales. For gingerich, it may take a little more effort to put forward this view, because he originally claimed that the suborder HYMENOPTERA is a close relative of whales. In Greece, the word "whale" stands for sea behemoth. We divide whales into two categories: toothed whales: toothed marine behemoths, such as sperm whales, killer whales, dolphins and porpoises. Baleen whale; Fin whale In fact, these beards are horned teeth that grow in the mouth. They are used to filter water and catch shrimps and other small animals that whales eat. These teeth replace teeth. As far as the whole marine mammals are concerned, whales have the most species and the largest number. Whales can be divided into two categories: one is called baleen whales, which have no teeth in their mouths and only beards; The other is called toothed whale, which keeps its teeth in its mouth when it is not needed. Although there are not many kinds of baleen whales, they are huge and become the main hunting targets of human beings. There are blue whales with huge bodies, right whales with slow movements and generally large heads, humpback whales with short arms and funny movements, minke whales with small mouthparts and so on. There are many kinds of toothed whales, except sperm whales, the others are generally small, such as killer whales and dolphins. Although the whale's body varies in length and thickness, it is always streamlined and looks like a fish, so people call it a whale. However, whales are animals. It also like people, constantly surfaced to breathe air. Sometimes on the sea, we can see the white fog columns ejected by whales when they exhale, some of which are as high as ten meters, like fountains, which are very spectacular. Whale training

Whales are mammals that live in water all their lives. They are so dependent on water that they can't live without it. In order to adapt to life in water and reduce resistance, their hind limbs disappear and their forelimbs become paddles. The body becomes streamlined, like a fish. So their diving ability is very strong. Dolphins (small toothed whales) can dive to a depth of 1 00-300m and stay for 4-5 minutes, fin whales can stay underwater at a depth of 300-500m1hour, and sperm whales (the largest toothed whales) can dive below1000m and stay in the water for 2 hours. 1955, a sperm whale was found dead in the sea near Ecuador, and its diving depth reached1133m. A sperm whale was found entangled in a cable at a depth of 2200 meters near Lisbon, Portugal, which is the deepest record of mammal diving so far. 1969, a sperm whale was able to swim to the surface after diving 1: 52. After people killed it, they found a small shark in its stomach that had just been swallowed an hour ago. According to analysis, this shark only lives in the depth of 3 192 meters. It can be seen that sperm whales can dive to a depth of 3000 meters in the ocean.

Whale herd

Divide whales into two groups:

Toothed whale: toothed marine behemoths, such as sperm whales and killer whales, and their toothed whales.

The teeth are very sharp.

Baleen whale: A whale with a long beard. In fact, these long beards are horned teeth that grow in the mouth and are used to filter water and catch shrimps and other small animals eaten by whales. These teeth replace teeth. Whales are viviparous mammals, not fish. It takes a year for calves to grow up on breast milk. Fish are oviparous vertebrates. Parent fish generally have no habit of taking care of small fish. Whale's "fins" actually evolved from limbs. Fish is not. Whales breathe with their lungs; Fish breathe through gills. Whales are warm-blooded animals; Fish are warm-blooded animals. You can't tell a whale from a fish by whether it has scales or not. Because many fish have no scales. According to the species, baleen whales have two different hunting methods. Degreasing type: For example, when the beluga whale swims slowly, it filters plankton, with its mouth half open and water flowing in from all the holes. Swallowing type 1: When this whale approaches a big beach of shrimp on the bottom of the sea, it opens its mouth to swallow a lot of water and puts it into the whale.

There is a slender, folded abdomen. As soon as the mouth is closed, the whale tongue rolls up the water filtered by the whale's teeth. For example, a blue whale can swallow 25,000 liters of water at a time. Swallowing type 2: The baleen whale opens its mouth to swallow the fish and shrimp together with the water, then filters out the water through the filter plate, and then swallows the fish and shrimp into its stomach. Every year, some whales leave the food-rich polar ocean to find warmer waters to give birth to their offspring. They traveled thousands of kilometers in a certain period of time a few months later. Every winter, many tourists go to Wan Li by boat to meet them in the Hawaiian Sea and the Gulf of Mexico. For sperm whales, males cannot migrate because there are not enough squid in the breeding area.

Whale species

Species of whales: As far as the whole marine mammals are concerned, whales have the most species and the largest number. Whales can be divided into two categories: one is called baleen whales, which have no teeth in their mouths and only beards; The other is called toothed whale, which keeps its teeth in its mouth when it is not needed. Although there are not many kinds of baleen whales, they are huge and become the most important hunting targets for human beings. There are blue whales with huge bodies, right whales with slow movements and generally large heads, humpback whales with short arms and funny movements, minke whales with small noses and so on. There are many kinds of toothed whales. Except for sperm whales, others are generally small, such as killer whales. Although the whale's body varies in length and thickness, it is always streamlined and looks like a fish, so people call it a whale. However, whales are animals. It also like people, constantly surfaced to breathe air. Sometimes on the sea, we can see the white fog columns ejected by whales when they exhale, some of which are as high as ten meters, like fountains, which are very spectacular.