Chinese name: cetacean Latin scientific name: cetacean kingdom: animal kingdom: chordates? Class: Mammals? Subclass (Mammals): Euthera? (Mammalia) Order: Cetacea: Mystic Cetacea and Toothed Cetacea Distribution area: Most of them are in the ocean, and very few are in rivers. Number of species included: about 98 species (there are more than 30 species in China sea area). English names: history of cetacean zoology, morphological characteristics, food species, biological sonar, population status, conservation organization, cetacean overview, secondary order, subordinate classification, baleen cetacea, odontacea, archacetacea, zoological history. From an anatomical point of view, many characteristics of cetaceans have appeared. However, anatomical evidence is not enough to answer many questions about the origin of cetaceans. However, from the biochemical and genetic point of view, cetaceans are closely related to ungulates, and the fossil record (about 50 million years ago) also supports that cetaceans evolved from ungulates. The ancestors of cetaceans may be terrestrial ungulates from North America, Europe and Asia-the family Oribatidae. Some members of middle-clawed animals are petite as domestic dogs and some are tall as bears, but the evolution process of many animals is from small to large, so whales may have evolved from small middle-clawed animals. It is speculated that these middle-clawed animals, with few teeth, lived in shallow waters, and gradually changed into amphibious life forms in the long evolution process, and then became various whales and dolphins. The earliest cetaceans were ancient cetaceans and protocetaceans. Primitive oceans all appeared 50 million years ago, and fossils are distributed in Asia, Africa and North America. Scientists know more about the ancient Pakistani whale (also known as Baki whale) found in Pakistan today. This kind of biological fossil, which lived 50-53 million years ago, has a narrow ventricle and still has hind limbs. At the same time, the fossil evidence found in Indian rock strata also shows that there are unimaginable high ecological differences among early cetaceans. The higher cetacean is the family Gulongidae, which was once considered a reptile. Animals in this family lived about 38-45 million years ago. Although they were first discovered by American geologists in Louisiana, similar fossils are widely found in New Zealand and even in Antarctica. This discovery shows that archaea had spread to the southern sea 40 million years ago. Another branch of higher archaea is Dorudontinae, which contains at least 6 species of animals. They have a narrow upper jaw and may be filter-feeding. Or, like most toothed whales, they can use this structure to catch fish, squid and birds quickly. After a long evolutionary process, archaea became extinct in Oligocene. However, the other two branches of the cetacean family, Mystic Whales and Toothed Whales, have derived nearly 65,438+000 species from 65,438+07 families. Morphological characteristics cetaceans are 1 ~ 30 meters long, fish-like, with * * * skin, only a few hairs on the snout, and no sweat glands and sebaceous glands. The forelimb is fin-shaped, and the hind limb is completely degenerated, leaving only 1 pair of small bones in the body. The skin at the tail expands left and right to form a horizontal caudal fin. There is no auricle, because there is 1 layer of fat under the skin, which can keep warm, reduce the proportion of the body and be beneficial to swimming. Some species have dorsal fins. Small eyes, no transient membrane, no lacrimal gland, poor vision. There are 1 ~ 2 external nostrils, located on the top of the head, commonly known as spray holes. Although there is no auricle, the hearing is sensitive. The left and right lungs have 1 lobe. Breastfeeding in water. The stomach is divided into four chambers, and the average life span in natural environment is 50 to 100 years. Cetaceans are completely aquatic mammals, and some mainly rely on echolocation to find food and avoid enemies. They generally feed on mollusks, fish and zooplankton, and some species can also prey on seals and seals. You must take a deep breath every once in a while. Generally, it swims from high latitude cold water area to low latitude hot water area to give birth in winter, and swims back to high latitude cold water area from low latitude to prey in summer. Food types generally feed on mollusks, fish and zooplankton, and some species can also prey on seals, seals and so on. Biological sonar is not a patent of human science and technology. Many animals have their own sonar. Bats emit 10-20 ultrasonic pulses per second with their throats and receive echoes with their ears. With this "active sonar", they can detect tiny insects and wire obstacles with a thickness of 0. 1 mm ... moths and other insects also have "passive sonar", which can clearly hear the ultrasonic waves of bats 40 meters away, so they often avoid attacks. But some bats can use high-frequency ultrasound or low-frequency ultrasound that insects can't hear, so the hit rate of catching insects is still very high. It seems that animals are also engaged in "sonar warfare" like humans! Marine mammals such as dolphins and whales have "underwater sonar", which can generate very definite signals to explore food and communicate with each other. Many kinds of whales use sound to detect and communicate, the frequency is much lower than that of dolphins, and the range is much farther. Other marine mammals, such as seals and sea lions, also send out sonar signals for detection. Dolphin sonar has a high sensitivity. It can find a metal wire with a diameter of 0.2mm and a nylon rope with a diameter of 1 mm several meters away, distinguish two signals with a time difference of 200ps, find fish schools hundreds of meters away, and walk through a pool full of bamboo poles flexibly and quickly blindfolded without touching them. Dolphin sonar has a strong "target recognition" ability, which can not only identify different fish and distinguish different materials such as brass, aluminum, bakelite and plastic, but also distinguish the echo of its own voice from the sound waves played back by the person who recorded its voice. The anti-jamming ability of dolphin sonar is also amazing. If there is noise interference, it will increase the call intensity over the noise so that its judgment will not be affected. And dolphin sonar also has the ability to express feelings. It has been proved that dolphins are animals with "language", and their "dialogue" is carried out through their sonar system. Their sonar system has a clear "division of labor", which is used for positioning, communication and alarm respectively, and has the special function of frequency modulation and phase modulation. Animals that have lived in the depths of the extremely dark ocean all their lives have to use sonar and other means to search for prey and avoid attacks. The performance of their sonar is far beyond the capabilities of modern human technology. Solving these mysteries of animal sonar has always been an important research topic of modern sonar technology. The "sonar" invented by us humans was invented through the principle of whales and dolphins. Due to the deterioration of the environment and the mass killing of human beings, cetaceans, especially some large members, are widely killed because of their high economic value, and many cetaceans are on the verge of extinction. The International Whaling Commission (IWC) is an international organization responsible for whaling and cetacean protection. After commercial whaling led to a sharp decline in whale population, the International Whaling Commission decided to take action to protect whales. These include a temporary ban on commercial whaling from 1986, and the establishment of Indian Ocean Whale Sanctuary in 1979 and Southern Ocean Whale Sanctuary in 1994 respectively. However, since 1986, some countries, such as Japan and Norway, have taken advantage of the loopholes in the resolution of the International Whaling Commission to kill at least 25,000 whales or dolphins every year under the banner of "scientific whaling". Other countries that kill whales are Norway, Iceland and Japan, as well as some indigenous tribes in Siberia, Alaska and northern Canada. Conservation organizations such as the International Whaling Commission, Greenpeace, sea shepherd conservation society and OPS (Marine Protection Organization). Overview of cetaceans The existing species can be divided into baleen whales and toothed whales. The suborder baleen whales is huge, and the smallest species is more than 6 meters long. There are no teeth in the mouth. There are 150 ~ 400 horny baleen on both sides of the maxilla. The color, quantity and shape of baleen vary from species to species, which is an important basis for classification. 2 external nostrils, located on the top of the head. The head is particularly large, and some species can reach 1/3 of the body length. There are only 1 ~ 2 pairs of ribs connecting the small sternum, without clavicle, and the flippers are generally 4 fingers. Have a cecum. They feed on krill and cephalopods, and some also live in eat small fish and benthic shellfish. There are 3 families 10 species, all of which are marine. Such as right whales, blue whales, gray whales, fin whales, humpback whales, great fin whales (minke whales) and minke whales (minke whales); Only a few species of toothed whales were born in fresh water, and most of them were born in the sea. They come in all sizes. There are teeth in the mouth, only 1 external nostril. Flippers usually have five fingers. There is no cecum except puffer fish. It mainly feeds on squid, crustaceans and fish. * * * Including 7 families and more than 80 species. Such as baiji, sperm whale, narwhal, dolphin, Chinese white dolphin, finless porpoise and killer whale. Cetaceans that have entered the water twice are rare aquatic species among mammals, and dolphins are one of them. They evolved from Artiodactyla in terrestrial mammals and returned to the water about 50 million years ago. Uncovering the evolutionary history of cetaceans and deciphering the genetic code of dolphins is a rare change in the life history of mammals, and their living habits have changed from terrestrial to completely aquatic. Drastic environmental changes have led to significant changes in physiology and structure to adapt to aquatic life, such as having a thickened subcutaneous fat layer (whale oil), the ability of long-term diving and echolocation, and a powerful muscle system to support underwater sports. Although people have learned a lot about the adaptive characteristics of physiological morphology, the molecular basis of these characteristics has not been systematically solved. Whales rely on keen hearing to survive underwater, but different whales show great differences in hearing ability. Baleen whales can receive infrasound waves with a frequency that is too low for humans to detect, which enables them to communicate over long distances, while toothed whales rely on ultrasonic waves, which are too high for humans to hear. According to the report published in the Journal of Contemporary Biology on June 8, 2007, researchers found evidence from the fossils of early extinct whale species, which can prove that the differences in whale hearing ability only appeared after they evolved into complete aquatic animals. Based on the study of "prehistoric whales" who can live both in water and on land, the researchers found that their auditory system is more similar to their close relatives on land, even cloven-hoofed animals such as pigs, hippos and camels. Researchers analyzed the remains of primitive whales 45 million years ago, which were found in deep-sea sediments in Togo, West Africa. The researchers studied the bones of two early cetaceans and the cavity surrounding the auditory organs. The scanned images enable them to analyze the cavity of the petrous part of the temporal bone to protect hearing and balance organs. Based on the scanned images provided by the scanner, a cavity model can be established to simulate the auditory organs of animals when they are alive. However, this work is long and difficult, because the fossil cavity is full of sediments and crystallized to a certain extent, and the temporal bone of whales is thick and dense, which reduces the quality of scanned images and often hinders the progress of analysis. The scanning results still show that the auditory system of early whales is similar to their close relatives on land. The infrasound and ultrasonic hearing possessed by modern whales did not appear until the whales returned to the sea. Subordinate classification cetaceans can be divided into two suborders: Mystic Cetaceans and Toothed Cetaceans, that is, the existing species of Mystic Cetaceans and Toothed Cetaceans. An suborder of baleen whales, with the largest living animal species in the world. There are 4 families 17 species with complete data, all of which are marine (note: there are some different opinions on the subfamily of baleen suborder). It is huge, and the smallest species is more than 6 meters long. There are no teeth in the mouth. There are 150 ~ 400 horny baleen on both sides of the maxilla. The color, quantity and shape of baleen vary from species to species, which is an important basis for classification. 2 external nostrils, located on the top of the head. The head is particularly large, and some species can reach 1/3 of the body length. There are only 1 ~ 2 pairs of ribs connecting the small sternum, without clavicle, and the flippers are generally 4 fingers. Have a cecum. They use baleen to filter plankton in seawater. They feed on krill and cephalopods, and some also live in eat small fish and benthic shellfish. Toothed whales come in different sizes. There are teeth in the mouth, only 1 external nostril. Flippers usually have five fingers. There is no cecum except puffer fish. This animal has a unique ability to perceive the environment by echolocation. Mainly feed on squid, squid, crustaceans and fish. Two branches of archaea survived, namely toothed whales and baleen whales.