Historical origin
Crocodiles are the earliest and most primitive reptiles found so far. It evolved from Triassic to Cretaceous (about 200 million years ago) and is still a semi-aquatic fierce reptile. It is a contemporary animal with dinosaurs. The extinction of dinosaurs is already a fossil, whether it is environmental impact or its own reasons. The existence of crocodile proves the strength of its life. crocodile
Crocodiles attract special attention because of their position in evolutionary history: crocodiles are the last link between living creatures and prehistoric dinosaurs and reptiles. At the same time, crocodiles are close relatives of birds. Found a large number of crocodile fossils; Three of the four suborders are extinct. According to these extensive fossil records, a clear relationship can be established between crocodiles and other vertebrates. Crocodile is a wild animal with high ecological, scientific and economic value. Siamese crocodiles belong to reptiles, crocodiles and crocodiles, and are national second-class protected wild animals. It has the advantages of strong reproductive ability, fast growth rate, strong disease resistance and excellent leather, and is one of the crocodiles with the largest number of artificial crocodiles in China. It is usually a huge, bulky reptile, which is slightly similar to lizard in appearance, but slightly larger than it and belongs to carnivores. At present, there are 23 recognized crocodile species. According to historical records, crocodiles were recorded in ancient China, and they were called crocodiles in the Book of Rites. Later, Han Yu in the Tang Dynasty wrote "Sacrificing Crocodiles", just like a thief's article, which was righteous and harsh, just to scare off crocodiles. In Ming Dynasty, Li Shizhen listed crocodiles as medicinal in Compendium of Materia Medica "Scale-Crocodile-Solution: Dragon Map" and defined their medicinal properties as "Indication: heart disease" and "dampness causing disease", which undoubtedly explained the role of crocodiles in human life. In modern times, crocodile skins are used to make luxury goods to show their value. In people's minds, crocodiles are "evil fish". When it comes to crocodiles, I immediately think of maw, dense and sharp teeth, hard armor and ready to eat people. It has keen vision and hearing, clumsy appearance, but very flexible movements. Crocodiles grow like this just to eat meat. All animals, including people, are its food. No matter how fierce an animal sees it, it can only take the initiative to avoid it and never dare to provoke it easily. The late Cretaceous is an important period in the evolutionary history of mammals. At that time, many populations began to differentiate to adapt to different microenvironments. David kross said: "Crocodiles have become more and more diverse since the late Cretaceous, from 5 meters long to less than 1 meter to meet the needs of different living environments. Establishing the relationship between extinct species and modern animals and plants is helpful to study the geographical structure of the past. In the past, a large number of fossils were found in the northern hemisphere. Before Madagascar was discovered, there were very few fossils in the southern hemisphere and Gondwana. According to the early theory of transcontinental species discovery in the southern hemisphere, there is a huge "bridge" between continents today. But now, scientists believe that Africa was first separated from Gondwana1650,000 years ago, while India-Pakistan subcontinent, Madagascar, South America and Antarctica were connected for a long time, so plants and animals were scattered everywhere.
Edit the geographical distribution of this part.
Crocodiles are vertebrate reptiles, distributed in rivers, lakes and coasts from tropical to subtropical. There are many crocodile families and genera, and there are more than 23 crocodile species in existence. Most of them are fierce and violent, like to eat small animals such as fish and frogs, and even kill people and animals. Its representative crocodile Crocodile Bay is 1 crocodile, also known as Crocodile Bay or Crocodile Sea. Distributed in Southeast Asia to the northern coast of Australia. It is 6 ~ 7 meters long and weighs about 1 ton. It is the largest reptile in existence. Crocodiles live on the other side of the bay or the sea.
Edit the morphological characteristics of this paragraph
Appearance characteristics
Crocodiles refer to crocodiles widely distributed all over the world. Stands for crocodile-Nile crocodile.
It is 1 species of crocodile, also known as crocodile or crocodile. Distributed in Southeast Asia to the northern coast of Australia. It is 6 ~ 7 meters long and weighs about 1 ton. It is the largest reptile in existence. Nile crocodiles live across the bay or the ocean. Archaeological findings show that crocodiles are about 12 meters long and weigh about 10 tons, but most crocodiles are about 6 meters long and weigh about 1 ton on average. The lower jaw is strong, with many tapered teeth, short legs, claws and webbed toes. The tail is long and thick with scales.
Special phenomenon
Crocodile Crocodile (Crocodile) is the only surviving Yi Long. As a cold-blooded egg-laying animal, it has not changed much for a long time, and it is the only predator and scavenger in water or land. It belongs to vertebrates, amphibians and reptiles. Most of them are fierce and violent. They like to eat small animals such as fish and frogs, and even kill people and animals. According to records, there are more than 20 kinds of crocodiles in the world, among which Chinese alligator, Thai crocodile and Nile crocodile are all famous. At present, the largest crocodile breeding base in China is Panyu Farm in Guangzhou, covering an area of nearly 70 hectares, with nearly 654.38+million crocodiles, such as bay crocodiles, Nile crocodiles, Chinese alligators and South American alligators. crocodile
Lacrimal gland was first known in Han Dynasty, recorded in Tang and Song Dynasties, and occasionally found in coastal islands since Ming and Qing Dynasties. As the saying goes, "crocodile tears" are actually true. Crocodiles really shed tears, but that's not because they are sad. It has long been thought that crocodiles are excreting excess salt in their bodies. Sea turtles, sea snakes, sea lizards, other marine reptiles and some seabirds all have salt glands near their eyes. Salt glands enable these animals to remove excess salt from seawater and obtain fresh water. Therefore, salt glands are their natural "seawater desalinators". So people think crocodile tears are also the reason. The excretory function of crocodile kidney is not perfect, and the excess salt in the body depends on a special salt gland to excrete. The salt glands of crocodiles are located near the eyes. But this is just a guess. It was not until 1970 that biologists detected the composition of crocodile tears and found that the salt content of crocodile tears increased after living in seawater for a period of time. This seems to prove that crocodiles have the same salt glands in their eyes as turtles, so they have been written into zoological monographs and textbooks. On the other hand, this experiment shows that the salt content of crocodile tears is obviously lower than that of salt gland secretions of marine reptiles such as turtles and sea snakes, so some biologists (including those who did this experiment) think that it actually denies the hypothesis that crocodile eyes have salt glands. The debate ended with 198 1. That year, taplin E. Taplin and Gordon C. Grigg of the University of Sydney, Australia, noticed a clear liquid on the surface of crocodile tongue, which they suspected was the secretion of crocodile salt glands. But the speed of liquid secretion is too slow to collect and analyze. They injected salt water into crocodiles to stimulate the secretion of salt glands, but they failed. Finally, they used the method of injecting methacholine into crocodiles-previous experiments showed that injecting methacholine into other marine reptiles could stimulate the secretion of salt glands. As expected, the crocodile's tongue constantly secretes liquid, which can be collected by syringe, and the content of sodium, chlorine and potassium ions can be analyzed to determine the osmotic pressure. They also collected crocodile tears for comparison. The results show that the salt concentration of these secretions is much higher than that of blood, about 3 ~ 6 times that of blood, and the osmotic pressure is 3.5 times that of blood, which is equivalent to seawater. Although the salt in tears has also increased, it is only about twice the blood salt concentration. Subsequently, they dissected the crocodile's tongue and found salt glands on the mucosa of the tongue, which are similar in structure to other marine reptiles, especially the salt glands under the tongue of sea snakes. Since then, other people's research has also confirmed this discovery. It seems that crocodiles excrete salt through secretions on their tongues rather than tears. So, what does crocodile's tears do? Crocodiles usually stay on land for a long time before they start to secrete tears, which are secreted from behind the blink membrane. Blinking membrane is a transparent eyelid. When the crocodile dives into the water, it can not only see the underwater situation clearly, but also protect its eyes. Another function of the instant film is to moisten the eyes, which requires tears for lubrication. Do crocodiles really cry when they eat? Kent fleet, a zoologist at the University of Florida, observed and photographed four Caiman crocodiles and three alligators eating on land in crocodile farm in 2007, and found that five of them did shed tears while eating, and some even had blisters on their eyes. They eat processed food such as dog food. Of course, there is no need to cry for these foods. Brett speculated that this is because crocodiles eat by blowing, forcing the air in the sinuses to mix with tears. However, the statement that crocodile tears are draining salt is still widely circulated in textbooks, popular science books and knowledge contests. Obviously, of course, persuasive legends and stories are not enough to rely on, and textbooks are not necessarily completely reliable.
Edit this paragraph of crocodile discoloration.
On June 20th,10, 12, near Gainesville, Florida, USA, Louis Guillette, a 55-year-old biology professor, changed his color.
Captured the wonderful moment of crocodile "discoloration" in the lake. When the sun rises on the lake, the sky reflects on the crocodile's wet back, so its exposed part turns blue. But this scene only lasted a few minutes and then disappeared.
Edit the living habits of this paragraph.
Living environment living in fresh water (at the intersection of a river bend and a bay). Crocodiles mostly live in rivers, lakes and watery swamps in tropical and subtropical regions, only a few live in temperate regions, and some live in shallows near the coast. It has a long face and a long mouth, and there is a saying that "the king of the world is not like a crocodile at all". Crocodiles are rich in ornamental value. Crocodiles also have many medicinal and health functions. Crocodiles are also valuable food. Because there are treasures everywhere, some countries in the world actively develop crocodile farming.
Growth and reproduction
The environment is in a tree-lined hill near Danshui River (more than 60,000 meters from the sea). They use their tails to sweep out a platform of 7-8 meters. There is a nest for crocodile eggs on the platform, with a diameter of 3 meters. The bird's nest is about 4 meters away from the river and is made of leaves. There are about 50 white hard-shell eggs in each nest, the size is about 80×55 mm; Female crocodiles wait by the nest, always wagging their tails and watering the nest, keeping the temperature at 30 ~ 33℃ and incubating for 75 ~ 90 days; The larval body length is 240mm, 1 year can reach 480mm, and it reaches 1 156mm in three years, weighing 5.2kg ... The crocodile is fierce and unruly. Adult crocodiles are often underwater, with only their eyes and nose exposed. They have keen eyes and ears and will sink immediately when they are frightened. In the afternoon, I float in the sun, and at night, my eyes are bright. The little crocodile is red. Crocodiles mate for several hours from May to June, while fertilization only takes 1 ~ 2 minutes. Laying eggs in July and August. Male crocodiles monopolize the territory, driving away invaders, and a male leads a group of females. Eat fish, frogs, shrimps, crabs, turtles and soft-shelled turtles. Strong chewing ability, can break the hard armor. Crocodile eggs are hatched by the heat of the sun and the heat of wet fermentation of weeds. The sex of young crocodiles is determined by the incubation temperature, but female crocodiles will balance the proportion of their children. They will nest on sunny slopes with higher temperature, or on low-lying shelters with lower temperature. 20-90 eggs will be laid at a time. The reason why the adaptive crocodile can survive for 65438+ billion years is that it may be the animal with the strongest adaptability to the environment so far, and its adaptability to the environment is shown in the following aspects:
Crocodile predation (6 pictures) 1. The evolution of the head is exquisite, which can ensure that only the ears and nose are exposed to the water during hunting, greatly maintaining the concealment. 2. In reptiles, it has an incredibly developed heart with 4 atria, while in normal reptiles, it has only 3 atria, which is close to the level of mammals. 3. When hunting, the heart can transport most oxygen-enriched blood to the tail and head, which greatly enhances the explosive force. The brain has evolved the cerebral cortex, so its IQ is high.
eating habits
Crocodiles mainly feed on fish, waterfowl, rabbits and frogs, and belong to carnivores.
Edit the population status of this section.
Endangered population 0 1. Indian fish-eating crocodiles: endangered. There are still a certain number of farms in India, and there are few breeding records in zoos. 02. Malay crocodile: Malay crocodile is an endangered animal, which can successfully breed in farms in Thailand, Bronx Zoo in the United States and Miami Zoo. 03. Orinoco crocodiles: Orinoco crocodiles have never bred in zoos, but they can breed on some private farms. 04. Alligator: Alligator is the most widely distributed and abundant species in Alligator subfamily, but it is still an endangered species. 05. Cuban alligator: The Cuban alligator is an endangered species protected by government laws. It can breed in some zoos in the United States and farms in the United States and Cuba. 06. Moliere Crocodile: Although it is protected by law, Moliere Crocodile is still poached in large quantities and belongs to an endangered species. Crocodiles in Morelj have been successfully bred in some zoos. Nile crocodiles: Some different populations of Nile crocodiles are listed as endangered, while others are listed as vulnerable. 08. African alligator: African alligator is an endangered species, which was successfully bred in Miami Zoo, USA. 09. Swamp Crocodiles: Swamp crocodiles are a fragile species and multiply in zoos in India. 10. Crocodiles in New Guinea: There are still a large number of crocodiles in New Guinea, which belong to vulnerable species and can be propagated in farms. 1 1. Crocodiles in the Philippines: Crocodiles are endangered species, with only about 100 in the wild. 12. Siamese crocodiles/Thai crocodiles: Thai crocodiles may be extinct in the wild, but there are still a large number of crocodiles raised artificially, which can cross with Gulf crocodiles. 13. Crocodiles: Although widely distributed, they are seriously threatened by crocodile skin trade and are listed as endangered species. At the same time, it is widely raised and can breed in many zoos and farms. 14. Australian freshwater crocodile/Qiang Sen crocodile: Although Australian freshwater crocodile is also threatened by poaching, it is strictly protected and belongs to a fragile species, and there are also a large number of farms. 15. African pygmy crocodile: it is listed as a moderately endangered or endangered species. Although it can be propagated under artificial breeding, no farm has been established. 16. Crocodiles in Mississippi: At present, the number of crocodiles in Mississippi has increased, and at the same time, there are a large number of artificial breeding, totaling one million, which is no longer a threatened species. 17. Chinese alligator: commonly known as Chinese alligator, it is an endangered species. There are only a few hundred crocodiles left in the wild, most of which gather in the Yangtze River, but the number of artificial breeding is still large. In addition to China, some zoos and farms, such as Bronx Zoo, have also successfully propagated. 18. caiman: two subspecies of caiman are listed as endangered, while others are listed as vulnerable, which can be artificially propagated in many places. In Florida, some individuals originally introduced as pets can form small-scale populations in parks and even sewers after escaping. 19. Caiman: The habitat of Caiman is a densely populated area in South America, which is seriously threatened by human activities and belongs to an endangered species. 20. Paraguayan caiman: Some scholars believe that this species is a subspecies of caiman. 2 1. ancient alligator: the skin of ancient alligator is not suitable for use, so its existing number is still relatively large and it is not an endangered species. 22. Crocodiles: Like alligators, alligator skins are not suitable for use, so there are still a large number of crocodiles in existence, which are not threatened species. 23. Black Caiman: Black Caiman is often killed by local people because it preys on livestock. Although protected by law, it is still an endangered species.
Edit the value and protection of this paragraph.
Medicinal and edible value
Medicinal value Crocodile is a wild animal with high scientific research value, ecological value and economic value. Crocodiles are full of treasures. Crocodile egg: rich in benign cholesterol, it can eliminate fat in blood vessels and help blood vessels to be smooth. Crocodile bile: It has the functions of detoxification, antipyretic, removing nebula and promoting metabolism, and can be used to treat bone cancer, liver cancer, bladder cancer, central retinitis and food poisoning, especially fatty liver and liver cirrhosis. In Thailand, a big crocodile breeding country, crocodile gall is very cherished and regarded as a panacea for treating female infertility and irregular menstruation. Crocodile liver: It has the functions of nourishing brain, promoting blood production, removing dampness, nourishing yin and liver, and improving eyesight, and can be used to treat senile cataract and vision loss. Crocodile heart: With Sanqi and Danshen, it can nourish the heart, soothe the nerves, promote blood circulation and remove blood stasis, and treat angina pectoris, myocardial hypoxia and coronary heart disease. Crocodile oil: it can relax meridians, relieve pain, refresh the mind, and especially moisturize the skin. Crocodile kidney: it can tonify kidney and solidify sperm. Crocodile A: It can soothe the liver and relieve depression, and regulate the spleen and stomach. It contains powerful anticancer substances and growth factors, and is used to prevent cancer and tumor new cells. The anticancer effect of this factor is tens of thousands of times that of other reptiles. Crocodile blood: According to the research published by the Royal Academy of Sciences, it contains antibacterial substances more powerful than all antibiotics found today, which can not only kill germs, but also destroy molds and even some viruses, that is, human beings have seen the dawn of human anti-cancer virus and AIDS virus from crocodile blood. Crocodile whip: Japanese research found that the aphrodisiac effect of crocodile whip is more magical than "Wei Ergang" and there are no side effects. Crocodile bone: it can treat and prevent rheumatic bone pain. Crocodile bone powder: contains a lot of active calcium and phosphorus, which can be used to treat osteoporosis in the elderly and calcium deficiency in children. Crocodile tail glue: It can not only nourish liver and kidney, invigorate qi, enhance cell vitality, but also protect skin, make skin more elastic, reduce and delay the early appearance of wrinkles, and also have satisfactory effects on allergies. Study on crocodile serum Crocodiles generally live in harsh environment. It stands to reason that there are many bacteria, which make crocodiles sick easily, but for a long time, crocodiles are almost healthy. If the crocodile has a little scratch on its skin and lives in water for a long time, it is reasonable to say that bacteria should have invaded the crocodile, but the crocodile is fine. A few days later, the crocodile's wound healed. After inspection, there are no pathogenic bacteria in the crocodile. Scientists did an experiment for this. Experimental scientists extract crocodile serum from crocodiles. They speculated that crocodile blood might have played a role. They wanted to prove whether their guess was correct, so they put crocodile serum and staphylococci harmful to people for 50 years in a sealed container, and observed it after a while-a fierce war began ... After the scientists came back, they took out the container and saw that crocodile serum defeated staphylococci. The obvious circle in the middle of the container is the forbidden growth area of bacteria formed by crocodile serum. As soon as staphylococcus enters that circle, it will be killed by crocodile serum immediately (the little spot outside is staphylococcus). I didn't expect crocodile serum to beat staphylococcus at once, which is also a reason why crocodiles have good resistance. If the experiment is successful, the fetal protein extracted from crocodile serum will become the strongest antibiotic in history and even fight AIDS. The idea that serum acts on peptide protein for sterilization comes from an outsider, a female TV reporter fullerton Smith who has nothing to do with medicine. She was ordered to make a TV movie about the living habits of crocodiles. Fullerton Smith found during filming that crocodiles often leave scars when they bite each other. One wound is in the east, and the other wound is in the west. If it is in humans, I don't know how many times I have to amputate. However, these fierce guys never get infected because of these injuries. It seems that their immune system is very strong, which can quickly eliminate the invading virus, bacteria and other microbial pollution. Fullerton Smith thought there must be a mystery, so he told the idea to a young crocodile expert. So, the two of them took great risks, took some crocodile blood (this is not an easy thing, you have to tie up the claws of the crocodile you caught first, and then draw the blood in the test tube from a blood vessel in the back of the crocodile's head), and sent the blood to American experts for help. Soon, American researchers isolated a peptide from crocodile blood, which can destroy bacterial cell membrane and amino acid chain. In the experiment, they found that crocodile protein with a large needle tip can kill most kinds of viruses, including the terrible drug-resistant Staphylococcus aureus (MRSA). Here, it is necessary to explain what is drug-resistant Staphylococcus aureus. In fact, there are some such bacteria in our skin and nasal cavity. When the body is weak, bacteria will take the opportunity to run into blood vessels and destroy muscles. Now that antibiotics are abused too much, bacteria are prone to drug resistance, and then they become M RSA. The initial symptoms of the disease are like being bitten by a bug, which is not easy to diagnose. Last year, it spread rapidly in American high schools, causing considerable panic. Protein extracted from crocodile blood this time can eliminate drug-resistant Staphylococcus aureus, which poses the greatest threat to human beings. In addition, in the experiment, it was found that this protein extract can target 8 different kinds of Candida albicans. Candida albicans is a kind of yeast, and people with low immunity are prone to infection. Killing HIV In fact, there are at least four unknown components in protein extracted from American crocodile blood. Scientists are trying to determine the chemical structure of these protein extracts. Once the chemical structure is determined, scientists can make super antibiotic drugs. These drugs will be on the shelves in the next 7 to 10 years. Biochemist Mark Machang has been devoted to the study of antibiotic characteristics of crocodiles. He said: "One day, you may be treated with crocodile blood products. I estimate that milk fat made from crocodile blood may be used for foot ulcers in diabetic patients or to prevent postoperative infection in burn patients. " However, he also admitted that because the crocodile's immune system may be too strong for humans, it needs to be neutralized to an acceptable strength for adults. After a period of research on crocodile's super immune system, scientists found that protein in crocodile's blood is also the bane of HIV. Adam Bree, an Australian scientist, said: "If you take an HIV test tube and compare the results after adding crocodile serum and human serum, you will find that crocodile serum kills much more HIV than human serum." Crocodiles deal with HIV in a different way from the human immune system. When the virus invades, the human immune system will immediately attack the virus. Antibodies of crocodile immune system will attach to bacteria, and bacteria will split and disintegrate, just like a fatal blow to the head with a gun. It seems that this time, we have to remember a special merit for crocodiles. After all, compared with crocodile skin used to make leather shoes, crocodile protein antibiotics that can kill MRSA have much greater credit. The history of human development is actually the history of human struggle against various diseases. From smallpox to plague, from diabetes to AIDS. While suffering from numerous diseases, human beings are also looking for their own way out. In fact, while nature gave us Pandora's box, it also gave us the antidote. Nature works so skillfully that cinchona trees grow in South America where malaria is common. Let Populus euphratica grow in the vast desert. Most Chinese medicines in China are taken from nature-centipede, scorpion, angelica, astragalus, etc. With the development of modern medicine, people can extract purer and more useful substances from animals and plants by more advanced means. However, this crocodile, which can provide blood for human beings to treat AIDS, is already an endangered wild animal. Populus euphratica, the only tree species in the desert, has also disappeared in large numbers, and animals and plants are extinct every minute on the earth. Maybe there are animals and plants like crocodiles that can help people. When all the plants and animals on the earth fall down one by one, it will be human beings who fall down last. However, when I learned that crocodiles, which are not very close to daily life, can actually help people treat infectious diseases and AIDS, I believe most people will not think crocodiles are ugly animals. What is really ugly is human beings who destroy the living environment of animals and plants. Crocodile serum can fight many viruses. In fact, protecting animals is also protecting human beings.