The whale is a mammal that is the largest of the animals that exist in the world. Our ancestors lived on land like cattle and sheep. Because they developed a love for food in the sea, they migrated to shallow bays. After a long period of time, the body slowly degenerated, and some parts of the body changed, becoming like a fish, and slowly adapted to life in the ocean.
[Edit this paragraph] Characteristics of whales
Whales are mammals living in the ocean. Some whales are very large, with the largest being up to 30 meters long and the smallest being over 6 meters long. At present, the largest known whale weighs about 160,000 kilograms. my country has discovered a whale weighing nearly 40,000 kilograms and about 17 meters long. The whale's body is like a fish and is spindle-shaped. The head is large, the eyes are small, and the ear shells are completely degenerated. 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 horizontal fin-shaped and is the main locomotion organ. Teethed or toothless. One or two nostrils, opened on the top of the head. The adult body is hairless (many species only retain some hair around the mouth). There is a thick layer of fat under the skin that keeps the body warm and reduces the body's specific gravity. Breathe with your lungs, inhale at the surface and then dive into the water. You can swim for 10 to 45 minutes. Generally feed on zooplankton, molluscs and fish. Viviparous, usually one calf per litter, and the calves are nursed with milk. But many people classify them as fish, but in fact they are not fish but mammals. Distributed in all oceans of the world.
Whales are found in all oceans of the world. It is an aquatic mammal that breathes with lungs. Its species are divided into two categories: baleen whales, toothless, with baleen and two nostrils, including fin whales, blue whales, humpback whales, gray whales and other species; toothed whales Class, with teeth, no baleen, and one nostril, including sperm whales, narwhals, killer whales and other species. Most of the oxygen in the ocean and 60% of the oxygen in the atmosphere is produced by phytoplankton. Baleen whales, however, can destroy phytoplankton's archenemy, zooplankton. In addition, toothed whales also help maintain the ecological balance of fish. The food of toothed whales is large molluscs that feed on fish. Therefore, without whales in the world, humans will perish.
The unique characteristic of cetaceans is their constant body temperature, which is about 35.5°C. The skin is bare, with no body hair, only a few bristles on the snout, and no sweat glands or sebaceous glands. Subcutaneous fat is thick and helps maintain body temperature and reduce the body's weight in water. The skull is well developed, but the brain is small, the face is large, and the forehead bone and maxilla are significantly extended, forming a very long snout. The neck is not obvious, the cervical vertebrae are healing, and the head is directly connected to the torso. The forelimbs are fin-shaped, the toes are not separated, and there are no claws. The joints of the elbow and wrist cannot move flexibly, so they are suitable for swimming in the water. The hind limbs have degenerated, but there are still remnants of the pelvis and femur, which are in the form of remaining bone fragments. The tail degenerates into a fin, and the skin at the end expands horizontally from left to right to form a pair of large tail lobes, but they are not supported by bones. The vertebrae gradually taper off the long and narrow tail trunk, and finally disappear before entering the tail fin. The tail fin is different from that of fish. It can move up and down and is the main organ for swimming. Some species also have dorsal fins for balance. Their bones have sponge-like tissue and there is more fat in the body cavity, which can increase the size of the body, reduce the specific gravity of the body, and increase buoyancy.
Their eyes are small, without tear glands and nictitating membranes, and their vision is poor. There is no external ear shell, and the external auditory canal is very thin, but the hearing is very sensitive, and it can feel ultrasonic waves, and rely on echolocation to find food, contact companions, or escape enemies. There are 1-2 external nostrils, located on the top of the head, commonly known as the blowholes. Generally, the farther the nostrils are located, the higher the degree of evolution. Breathe with the lungs. There are two lungs on the left and right. There are many capillaries in them. They are elastic and can help the circulation of oxygen and adapt to the gas exchange on the water. Every once in a while, you need to surface for ventilation. Can dive for longer periods of time. There are 10 to 20 pairs of ribs. The stomach is divided into 4 chambers. The kidneys are mostly tumor-like. The testicles of male animals are located in the abdominal cavity. The female animal gives birth and breastfeeds in the water. The uterus is bicornuate and has a pair of breasts located in the cleavage on both sides of the reproductive slit. There are slender nipples. The milk is rich in calcium, phosphorus and a large amount of fat. The young have teeth during embryonic life, but the teeth of baleen whales are replaced by baleen at birth, while the teeth of toothed whales are retained throughout their lives.
Cetaceans are mammals that live in water. They have the same physiological characteristics as land mammals, such as breathing with lungs, viviparous birth, etc., and also have some features that have evolved to adapt to the aquatic environment. The special physiological structure.
Whales are classified into kingdom Animel, phylum Chordata, class Mammrha, and order Cetacea.
Cetacea is divided into two sub-categories: The two orders are suborder Mysticeti, blaleenwhales and toothed whales (suborder Odo-ntoceti, toothedwhales). Scientifically speaking, the division of these two categories is mainly based on their different feeding methods. The suborder Mysticeti is the main group. The morphological characteristic is that they have no teeth, but they have large baleen, which can be used to filter plankton. Therefore, the main characteristics of the toothed whale suborder are that they have teeth and are predatory. The number and arrangement of their teeth are affected by their feeding habits. There are about 79 species in 13 families in the world.
Although whales have the word fish, they are actually not fish, but mammals, and many of them are very different from fish. For example, ordinary fish swing their tail fins left and right to move their bodies forward, but whales move their tail fins up and down. They use the flippers at the front to maintain body balance and control the direction of force. Some whales also have the upper end of their backs. There are fins that can keep the body vertical.
Whales are social animals. They usually live in groups in the sea. However, when whales breathe, they need to swim to the surface. At this time, whales use their heads. When you exhale, the moisture in the air will condense to form the familiar fountain shape. Experts can even identify the type of whale from the height, width and angle of the spray. There are many types, roughly divided into two categories: toothed whales and baleen whales.
There is a very thick layer of fat under the epidermis of whales, which is commonly known as whale oil, which can keep the whale body warm and can also be stored. Energy is used to supply emergency needs. Because the whale has many special structures that allow it to breathe and slow down its heart rate in the water for a long time, it will always take a long time before it sinks to the bottom of the sea. Resurface. In addition to having a structure for storing oxygen, when a certain part of the body needs a large amount of blood supply, the body also has a special function of concentrating the supply.
The water jets ejected by baleen whales are high and strong. The water column spouted by toothed whales is thick and short. Some fishermen can even judge the type of whale based on the water column.
Due to human hunting, at least 5 of the 13 species of whales in the world are currently endangered. Extinction. To protect whales, the International Whaling Commission banned commercial whaling in 1986, but this ban was relaxed in 1987, allowing limited whaling for "research purposes", despite widespread opposition. The country still kills whales in large numbers every year in the name of scientific research.
The whale comes to the surface to breathe every time. Different whales have different water columns. An experienced person can deduce the species, size and age of a whale by looking at the water column. We also learned that whales are not fish.