Their eyes are small, with no lacrimal glands or transient membranes, and their vision is poor. There is no outer ear shell, and the outer ear canal is very thin, but the hearing is very sensitive, and can feel the ultrasonic waves, relying on echolocation to find food, contact companions or escape from the enemy. There are 1-2 external nostrils, located on the top of the head, commonly known as the blowhole, and generally the more the nostrils are positioned against the latter the more evolved they are. Breathing with the lungs, the left and right each have a lobe lung, which has many capillaries, elastic, can help the circulation of oxygen, adapted to the gas exchange at the surface of the water, need to surface every once in a while to change the air, but also able to dive for a longer period of time. There are 10-20 pairs of ribs. The stomach is divided into 4 chambers. The kidneys are mostly verrucous.
The ancestors of cetaceans were originally land animals that walked on all fours, probably insectivores or carnivores that lived mainly along the seashore, but were later attracted by fish and other food in the water and returned to the sea from the land after a long period of time and gradually adapted to the marine life. The earliest whales appeared in about 55 million years ago. /FONT>36 million years ago in the middle of the Eocene Eocene, the first whale, the first toothed whales and the late Eocene proto whales, etc., they and the existing whales, the skull is relatively small, the nostrils are located in front of the head, has not yet been moved to the top of the head, and the teeth and ancient insectivorous, carnivorous teeth are almost the same, all are 44 or fewer than 44, teeth, the skull is also very similar, there are only a few different points, but they The teeth and skulls of the ancient insectivores and carnivores were also similar, with only a few differences.
Toothed cetaceans vary greatly in size, with the smallest species being only about 1 meter in length and the largest being more than 20 meters. The mouth has cone-shaped teeth, but the shape and number of teeth vary greatly from species to species, the least has only one single tooth, the most has dozens of teeth, and some are hidden in the gums and do not show, so it is also one of the important basis for classification. There is only 1 external nostril, so only a jet of water can be emitted when breathing. The skull is asymmetrical from side to side. The fins have 5 fingers. The sternum is large. No clavicle. No appendix. Feeds mainly on squid, fish, etc., and some also prey on seabirds, seals, and other large animals such as cetaceans. Baleen cetaceans in the world*** There are 8 families, about 34 genera and 72 species, including freshwater dolphins, sperm whales, saber-nosed whales, narwhals, spinner whales, spiny dolphins, porpoises, dolphins, and pilot cetaceans. Baleen whales are huge, and the smallest species are more than 6 meters long. There are no teeth in the mouth, only in the embryonic development can be seen degradation of the teeth, but the palate on the left and right sides of the upper jaw to the pharynx each have 150-400 comb-like arrangement of horny baleen. The color, shape and number of the whiskers vary from species to species and are one of the most important bases for classification. There are two external nostrils, located on the top of the head, which can emit two columns of water when breathing. The skull is extremely large, up to 1/3 of the body length in some species, and is symmetrical. The cervical vertebrae are fused or separated. Sternum is small, only 1?/FONT>2 pairs of ribs connected to the sternum, the thorax is incomplete. There is no clavicle. Flipper limbs generally with 4 fingers. The digestive tract has an appendix. Mainly feed on krill and other small crustaceans, some species also eat small schooling fish, as well as benthic fish and shellfish. There are three families of baleen whales, including right whales, gray whales, and fin whales,**** about 6 genera and 11 species. Cetaceans due to the great economic value, since ancient times is the object of human hunting, but in the past, due to the backward means of hunting, the amount of hunting is relatively small, is not enough to affect the number of whales. In modern times, people switched to hunting cetaceans with ships and artillery, which greatly increased the killing power, making the number of whales plummet, and many species are on the verge of extinction. Nowadays, whaling has gradually ceased to be a major concern for scientists who monitor the population and survival of cetaceans, as countries around the world impose strict limits on the number of cetaceans that can be captured each year. However, on a global scale, the unprecedented marine pollution caused by human economic development poses a great threat to cetaceans, which is far greater than that of killing, and the rapid development of industrialized fishing also greatly affects the food source of marine mammals such as cetaceans, which is another major factor affecting their survival. People used to imagine the ocean as a symbol of a vast and boundless free world and the possibility of engaging in adventurous activities, so while plundering marine resources with impunity, not only is there a large amount of ocean noise generated by the shipping industry and a large amount of ballast water discharged every year, but also a large amount of garbage dumped into the ocean, and about 100,000 types of chemicals reach the ocean through the discharge of sewage and the air, and organic chlorides, which are difficult to decompose, increase the number of marine organic compounds, which are also difficult to decompose, are also a major factor affecting their survival. Organic chlorides, which are difficult to decompose, have increased the organic content of the oceans, making marine pollution more and more serious and bringing about serious consequences. The results of modern scientific research show that the ocean is a giant container for storing carbon dioxide from exhaust gases, that the hot and cold sea current system has a great influence on the earth's climate, and that in the deep sea, where little research has been carried out, there are many unknown plants and animals that are beneficial to human beings, including many potential sources of food and medicines for human beings, which are of great value. Increasing levels of marine pollution will decimate these valuable resources. Due to the destruction of the ozone layer, living in the sea around the Antarctic krill population density has been sharply reduced, per 1,000 cubic meters of seawater inhabited by the number of krill tails has been from 1982 to 1983 before the 177.8 tails, a sharp decline in 1984-1985, 41.2 tails. Krill is a crustacean in the ocean, is an important bait for marine fish, cetaceans and other marine mammals, has an extremely important position in the marine biological chain, and it has also received great attention as the largest protein resource remaining on earth. Since cetaceans and other marine mammals are located at the end of the food chain, marine pollution, especially heavy metal pollution and other substances that have a radical effect, seriously weakened their immune system, thus making them extremely vulnerable to viruses and bacteria,. China's cetaceans are very rich in resources, so far found in China's waters has reached 9 families, 26 genera, 38 species, including both blue whales with a body length of more than 30 meters, and porpoises with a body length of only about 1 meter, in particular, also has a specialty freshwater cetaceans - albacore dolphins, which is a cetacean in a strange ballet. China's cetaceans in addition to the albino dolphin and the Chinese white dolphin 2 species are listed as national class I protected animals, all other species are listed as class II protected animals. The Earth's most--Blue Whale
Size
Newborn 7 meters, adult 24-27 meters; small blue whale newborn 6 meters, adult 21-22 meters.
Weight
Newborn weight about 2.5 tons, adult 100-120 tons.
Morphological features
Large body size, bluish-gray body color, mottled body surface, dorsal fin is small and blunt, posteriorly positioned, head is wide and flat, U-shaped, huge jet front, tail trunk is very thick, spouting up to 9 meters, when diving, may show caudal fin, streamlined body, many folds under the throat, baleen plate is medium-long, upper jaw is horizontal in lateral view.
Behavior and natural history
There are three distinct subspecies, the intermediate blue whale, which lives in the Southern Hemisphere, the smaller subspecies, which lives in the Northern Hemisphere, and the even smaller subspecies of the lesser blue whale, which lives in the tropical Southern Hemisphere. Adult whales rarely leap out of the water, usually at a 45-degree elevation angle, and then drop back down on the side of the belly lithium body. In some areas, feeding activity appears to take place in the evening or early morning, and group sizes are 1-2, with larger groups sometimes present in good feeding areas.
Distribution
Predominantly in cold waters and mid-ocean, on the edge of the continental shelf. Extant
About 6,000-14,000.
Habits
The blue whale is also known as the "razor whale". Mammalia, Cetacea, Cyprinidae. Widely distributed, found in the oceans from the Arctic to the Antarctic.
The blue whale is the largest animal on earth, an adult blue whale can grow to have lived on the earth's largest dinosaurs - Brachiosaurus weight more than two times, the weight of African elephants about 30 times. Blue whales are true giants of the sea, with an average length of about 26 meters, a record high of 33.5 meters, and an average weight of 150 tons. Such behemoths need a lot of food. An adult blue whale consumes about 1 million calories a day, equivalent to 1 ton of krill, which is its bulk food. Blue whales swim into the shallows and swallow mouthfuls of water and krill. The krill is filtered out by the tongue, which acts as a piston, forcing the water to flow out through a large sieve-like structure of baleen hanging from either side of the upper jaw. A blue whale's tongue is more than 3 meters thick and weighs more than an elephant.
Blue whales are lung-breathing mammals, so they need to come out of the water every 10-15 minutes to breathe. When they come to the surface, they expel carbon dioxide from their lungs through their nostrils before inhaling. The burning, powerful carbon dioxide exhaust from the nostrils is accompanied by a loud screeching sound and rolls nearby seawater out of the water up to a height of about 10 meters, resulting in a spectacular white column of fog on the surface.
Blue whales once roamed the world's oceans, and it is estimated that there were once 250,000 of these giants in the Southern Ocean alone. But in recent years, the relentless whaling industry has reduced the number of blue whales to less than 1 percent of that total. Determining the number of blue whales is difficult, with current estimates ranging from a few hundred to 11,000 in the Antarctic. This number, whether correct or not, is dangerously low compared to the number that once existed. Despite restrictions on whaling for the last 50 years and a mandatory ban on whaling in 1967, blue whales continue to be hunted commercially under the guise of scientific research.
Blue whales migrate great distances, and in the summer, they live in polar waters, feeding on the abundance of krill adjacent to the edge of the ice floes. , particularly addicted to krill. Blue whales eat, open the huge mouth, so that seawater and zooplankton together into the influx, there are a hundred rivers in the mouth of the situation, and then close the mouth, seawater from the baleen seam discharge, filtered down to the small animals, can be swallowed into the belly. When winter comes, they migrate to warm equatorial waters, traveling thousands of kilometers. One blue whale is known to travel more than 3,000 kilometers in just 47 days. Such long journeys take them away from their feeding bases and they do not eat for up to four months. They live off the stored energy they have accumulated.
Blue whales long enough to travel the world's oceans singly or in pairs can live to be 120 years old. Despite their solitary lifestyle, they have an advanced method of communicating over great distances, producing a low-frequency, high-intensity sound. Sound frequencies of up to 180 decibels have been recorded, which is the loudest noise known to be produced by motion and exceeds the noise produced by a jet airplane in flight. The sound can continue for up to 30 seconds and can be heard by other blue whales up to 1,610 kilometers away.
Blue whales are also the animal world's unrivaled Hercules. A blue whale traveling at 28 kilometers per hour can generate 1,250 kilowatts of power, equivalent to the pull of a medium-sized locomotive. A blue whale once dragged a 27-meter-long whaling speedboat for eight and a half hours, at an average speed of 9 kilometers per hour, when the speedboat was running at full power backward, but it was still pulled forward 74 kilometers.
Ventriloquist"--White Whale
Size
Newborn 1.5-1.6 meters, adult about 3-5 meters
Weight
Newborn weight of 80 kilograms, the weight of adults 0.4-1.5 tons. Morphological Characteristics
Very pale body color, showing a solitary white color, small head, rounded frontal ridge, dorsal spine shanks in place of dorsal fins, very short beak and broad lips, usually slow swimmer, very accessible, often floating peepers, not good at aerial stunts.
Behavior and natural history
Recognizing them in white waves and ice floes is not easy; one must watch for white objects that appear, grow larger, shrink, and then disappear, spending most of their time at or near the surface, moving in gentle undulating motions. Occasionally it will lift its head out of the water while swimming. On calm days, the jet can still be heard from hundreds of meters away, and group sizes range from 5-20; in summer, hundreds or even thousands may congregate near estuaries.
Distribution
Seasonally ice-covered waters in the Arctic and subarctic.
Existing
50,000-70,000
Habits
Beluga whales are authentic summer travelers, and thousands of them set out from the Arctic each July on their summer journey. From a few to tens of thousands, they swim to their vacation spots in great numbers. Along the way, they swim leisurely． The usual cold bays, estuaries, and deltas are now bustling with activity.
The beluga whale is the best "ventriloquist" in the cetacean kingdom, and they can make hundreds of sounds, and the sounds they make are so varied that they make people gasp in amazement. It's a rare treat to be able to hear the beluga's singing voice in person.
In order to understand the sound of beluga whales, scientists made live underwater recordings at a beluga whale resort in the estuary delta, and the results were far beyond what anyone could have imagined. They actually heard the roar of the beast, the cow's moo, the pig's grunt, the horse hissed, the bird's squeak, the woman's screams, the patient's moan, the baby crying ...... is really a variety of things, there is nothing strange. Beluga whales can also make hinge sounds, bells, steamboat sounds and so on.
The beluga whales keep "singing", in fact, in the self-indulgence, but also a kind of communication between companions, which is an important content of their summer vacation. The belugas look very excited as they enter the estuary, and they don't seem to be tired at all, despite the long distance they have traveled. In addition to "communicating" with their different songs, they also use their broad tail lobes to play in the water, half exposing their bodies to the water, a very beautiful gesture, and the tourists scramble to take this precious shot. Beluga whales can also play with a variety of "toys". A piece of wood, a piece of seaweed, a rock can become their object of play. They can hold a long piece of seaweed, a moment of diving, a moment of floating up, their mouths keep making joyful sounds. Sometimes they are obsessed with a basin-sized stone, first play with their mouths to arch over the stone, then the stone in their mouths to leap out of the water, and even better is that they will put the stone on top of their heads to perform on the water like acrobats.
The beluga whales are not only graceful, they are also extremely clean. Many beluga whales swim to the estuarine delta with many parasites attached to their bodies, making their appearance and body color very dirty, and they themselves seem to be extremely uncomfortable. At this point they dive down and roll under the river, turning over and over. Other belugas rub themselves on the gravel or gravel of the deltas and shoals. They roll over like this every day for hours on end. After a few days, all of the beluga's old skin is shed and replaced with new, white, neat and beautiful skin, with a new, beautiful body color.
Belugas are herd animals, and most of their vacation spots are concentrated in the northern latitudes. But some mischievous belugas seem to have a penchant for roaming independently of the group. Sometimes a single beluga travels south alone, swimming hundreds of kilometers in style, and surprises people by showing up at the mouth of the Heilongjiang River or the Firth of Forth in Scotland. Sometimes a beluga wandering along the Rhine A - road, visit Cologne, then visit Bonn, stayed for more than a month, tens of thousands of people in the boat and the shore to watch, become a local sensation of the big news.