Classification status
Eukaryote in eukaryotic domain
Fauna in the animal kingdom
chordata
A subclass of vertebrates.
Mammals; mammal
True beast subclass Tberia
origin
From the anatomical point of view, many characteristics of cetaceans show a high degree of adaptation to marine life. 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 water and gradually changed into amphibious life forms, and then became various whales and dolphins today in the long evolution process.
At present, the earliest known cetaceans are ancient cetaceans (protocetaceans).
Primitive oceans all appeared 50 million years ago, and fossils are distributed in Asia, Africa and North America. Scientists have learned more about Pakicetus, a biological fossil found in Pakistan today, which lived 53-50 million years ago. It is an animal with narrow ventricles and hind limbs, and its jet hole (nostril) moves backwards. 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 45-38 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 narrow maxilla and may be filter feeders. Or, like most toothed whales, they can catch fish, squid and birds quickly through this structure.
After a long evolutionary process, archaea finally died out in Oligocene. The other two branches of the cetacean family, Mysticeti and Odontoceti, have gone out of the past history and derived nearly 80 fascinating creatures of the 13 family, enriching our marine vitality.
morphological character
Completely aquatic mammals. Body length 1 ~ 30 meters, fish-like, naked skin, only a few hairs on the nose and mouth, 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. Some of them mainly rely on echolocation to find food and avoid enemies. 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. They generally feed on mollusks, fish and zooplankton, and some species can also prey on seals and seals. Distributed in the oceans of the world.
Biological description
Like all mammals, whales breathe with their lungs and are warm-blooded animals. Their young are breast-fed and have a little hair. The lungs are very big, and every breath is thoroughly ventilated. After diving, it is economical to use oxygen, so that whales can dive for 30 ~ 70 minutes, or even longer before they surface for air. Most small whales are shallow divers, while some big whales can dive deep. For example, sperm whales can dive 900 ~ 1 134 meters. The forelimbs of whales form fins, the hind limbs completely degenerate, the tail becomes a caudal fin, and the nostrils are at the upper part of the head. Of particular note is the blue whale. It is the largest living animal in the world, with a body length of 30 meters and a weight of 180 tons.
Whales are considered carnivores. Their food types range from microorganisms to large fish. All mammals, including whales, need sleep, but whales can only put one hemisphere to sleep by keeping awake breathing. So whales never sleep, but they can get the sleep they need. Whales sleep about eight hours a day.
Male whales use vas deferens to excrete sperm to female whales. After the fertilization process is completed, sperm and eggs are combined in the mother whale. A mother whale usually gives birth to a calf. Pregnancy is basically about one year. Some young whales may have to breastfeed for a year and have a longer feeding period. Some young whales are even weaned with their mothers for several years after birth. In their living environment, they will encounter the predation of sharks, so a very strong relationship will be established between mother and son. Some whales mature very late, about seven to ten years. The reproductive organs of whales are retracted to avoid resistance when swimming. The mother whale has 1 pair of nipples, and the milk is squeezed into the mouth of the calf through the contraction of the muscles around the breast to feed the calf. The life span of whales is about 60 to 70 years old.
branch
Cetaceans include about 80 species of large marine placental mammals. Whales belong to cetaceans, which also include dolphins and small whales. The definition of "whale" itself is vague and can include all whales, some large whales or whales belonging to a specific family. But killer whales and giant whales belong to dolphins. Whales can be divided into two suborders: baleen whales and toothed whales.
The existing species can be divided into baleen whales and toothed whales.
Mystical whales, suborder baleen whales
The baleen whale is the largest living animal species in the world. There are 3 families 10 species, all of which are marine.
The family Right Whales includes: glacier right whales, Antarctic right whales, mysterious right whales, capers and right whales (note: some of them are classified as new right whales).
Gray whales, such as the stout gray whale.
Balaenopteridae, such as: blue whale (blue whale, razor whale) Balaenoptera musculus, minke whale (minke whale) balaenoptera acutorostra, humpback whale (humpback whale, Megaptera novaeangliae, fin whale, fin whale, minke whale, mako whale, Brucella, Balaenoptera edeni, and Sei whale.
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. Only 1 ~ 2 pairs of ribs are connected to the small sternum, and there is no clavicle. 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.
Tooth jaw suborder
Only a few species of toothed whales were born in fresh water, and most of them were born in the sea. * * * Including 7 families and more than 80 species. (Note: There are some different opinions on Tooth Whale subfamily, which can be divided into three different groups: dolphins, beaked whales and sperm whales, and each group is divided into more than one family. )
Freshwater dolphin family, also known as freshwater dolphin family. Such as: Baiji dolphin, Indian puffer fish, Ganges puffer fish, Amazon puffer fish, Madeira puffer fish, Bolivian puffer fish and La Plata puffer fish.
Kingfishers, such as true dolphin kingfisher, short-billed true dolphin kingfisher, long-billed true dolphin kingfisher, bottlenose true dolphin, bottlenose dolphin, Amazon white dolphin, killer whale (killer whale, killer whale), dolphin, Chinese white dolphin, giant whale (sperm whale, black whale), big-nosed sperm whale, long-legged sperm whale, short-legged sperm whale, melon
The finless porpoise, such as the finless porpoise.
Monodontidae, such as narwhal (narwhal) Monodon monoceros, beluga whale Delphinapterus leucas, (note: sometimes puffer fish (short-nosed dolphin) Orcaella brevirostris also belong to this family. )
Superodontidae, such as the dense-toothed whale, a long-billed whale of Brucella.
physeteridae
Physeteridae Jr. is a small sperm whale, similar to Kogiidae breviceps and Kogiasimus.
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. This animal has a unique ability to perceive the environment by echolocation. Mainly feed on squid, squid, crustaceans and fish.
economic value
China is rich in cetacean resources and has a long history of whaling. Great economic value, edible meat, leather and whale brain oil can be extracted from industrial lubricants, fat can be made into engine oil, soap and candles, bones can be made into bone meal, and viscera can be made into vitamin preparations.
protect
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, Japan and Norway have killed more than 25,000 whales under the banner of "scientific whaling" because they took advantage of the loopholes in the resolution of the International Whaling Commission. At present, countries that kill whales include Norway, Iceland and Japan, as well as some indigenous tribes in Siberia, Alaska and northern Canada.
whale
Whales are mammals that live in the sea. Some whales are very big, and the maximum length can reach 30 meters. Whales are shaped like fish and are spindle-shaped. The head is big, the eyes are small, and the ear shell is completely degraded. 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, open at the top of the head. Adults are hairless (many species just 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 a calf, is fed with milk. But many people classify them as fish. In fact, they are not fish, but mammals. Distributed in the oceans of the world.
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 categories: baleen whales, toothless whales, baleen whales and two-nostril whales, such as baleen whales, blue whales, humpback whales and gray whales. Toothed whales have teeth, no baleen whales, only one nostril, such as sperm whales, narwhals, killer whales and so on. 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. The toothed whale's food is a large mollusk that feeds on fish. Therefore, without whales in the world, human beings will perish.
We divide whales into two groups:
Toothed whale: 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.
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, while 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.
1. According to the species, baleen whales have two different ways of hunting.
Degreasing type: For example, the beluga whale filters plankton in the process of slow swimming, with its mouth half open and water flowing in from the joint.
Swallowing type: When this whale approaches a big beach of shrimp at the bottom of the sea, it opens its mouth to swallow a lot of water and puts it into a collapsible belly. 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.
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.
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 strangled by a cable was found at a depth of 2200 meters near Lisbon, Portugal, which is the deepest record of mammal diving so far.
2. 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 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.
References:
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