Dogs, also known as "dogs" in Chinese, belong to Carnivora and are distributed all over the world.
Dogs, horses, cows, sheep, pigs and chickens are also called "six animals".
Some scientists believe that dogs were domesticated by early humans from gray wolves. The domestication time was from 40,000 years ago to 1.5 million years ago, and it has developed to this day. Known as "the most loyal friend of mankind", it is the pet with the highest feeding rate at present. Its life span is about ten years.
In China culture, dogs belong to one of the 12 Zodiacs, ranking 1 1 among the 12 Zodiacs.
Global quantitative editing
Dog is a very common canine mammal, and it is also the pet with the highest feeding rate.
According to United Nations statistics, there are about 600 million dogs in the world and about 200 million dogs in China. Dogs are the earliest domesticated animals.
Dominant contribution editor
Nurse dog: guarding human safety and property, guarding homes and nursing homes.
pet dog
Pet dogs (2)
Pet dog: companionship and enjoyment.
Hunting dog: hunting fee ...
Pastoral dogs: sheepdog, cattle dog. ...
Medical dogs: due to their optimistic nature, dogs are suitable for caring for and accompanying patients with mental illness, depression and autism (except violent patients); The premise is to choose a domesticated dog that won't make trouble, otherwise it may increase the burden and lead to a worse condition.
Dog care: take care of people who have difficulties in self-care and paralyzed people; Can help people take off their shoes/socks, insert cards to withdraw money, open/close doors, turn on/off lights, push/pull cars, and take things from the refrigerator.
Guide dog: Compared with guard dogs, it is more responsible to accompany its owner at all times, and most of the things of the owner really need the assistance of guide dogs; Guide the owner to cross the road, and the dog will go shopping alone.
Military dog: some countries have special military dog medals; Military dogs, police dogs, customs anti-drug dogs, airport gunpowder monitoring dogs ...
Search and rescue dogs: search and rescue when avalanches, earthquakes, fires and other disasters occur.
Traffic dogs: For example, Eskimos near the Arctic Circle and some people in northeast China use "sled dogs".
Show dogs: Most circuses have dogs specially used for performances, which have many skills and talents.
Experimental dog:
⑴ Medical experiment: In medical and pharmaceutical research, because the weight of mice is too different from that of human beings, dogs are often needed to do experiments.
Species evolution editor
Canine ancestors
Paper-cut dog photo album
Paper-cut dog photo album (20 photos)
No one knows exactly when the first interaction between man and wolf took place. Some scientists think it may be 50,000 years ago, because it took wild wolves at least so long to show today's genetic differences. At that time, humans and wolves were distributed in many places on the earth's surface, and the evolution process may have occurred in several different areas. Some scholars believe that wolves were domesticated from wild wolves to domestic animals for playing, hunting and housekeeping, that is, dogs, before 14000 years or even before 16000 years in Southeast Asia.
Dogs originated from wolves and have been recognized, but opinions vary around the specific place of birth and time. The earliest evidence of dog fossils comes from a mandible fossil in Germany 14000 years ago. These archaeological evidences support that dogs originated in southwest Asia or Europe. On the other hand, the characteristics of dog skeleton identification suggest that dogs may have originated from wolves, thus putting forward the origin theory of East Asian dogs. In addition, different breeds of dogs are very diverse in morphology, which seems to be inclined to the hypothesis that dogs originated from wolves of different geographical groups. Archaeology alone can hardly provide reliable clues about the origin of dogs. (Continued/Click: [2])
Domestication process
People and dogs live in harmony.
People and dogs live in harmony (7 photos)
Researchers at the University of Arizona in the United States unearthed two dog skulls at least 33,000 years ago from Belgium and Siberia, respectively, indicating that dogs have been tamed by humans as early as ancient times.
The researchers said that these two dogs have short noses and wide chins, while wild animals like wolves need long noses and narrow chins to catch their prey. On this basis, they think that this shows that our ancestors began to domesticate dogs long ago to resist danger and relieve loneliness. The researchers also believe that dogs may be the first animal domesticated by humans, which is much earlier than domestic animals. (Continued/Click: [3] )[4]
genetic code
Zhu Xuanxian's print "Dog"
Zhu Xuanxian's print "Dog"
The evolution of dogs is related to starch digestion: by comparing the whole genomes of dogs and wolves, researchers at Uppsala University revealed many changes in the evolution of wild dogs into human best friends. Unsurprisingly, many of these different areas affect the brain, which may explain the temperament difference between wolves and dogs. In addition, this comparative study also pointed out several areas related to digestion, including genes that help break down starch.
Researchers say that dogs may domesticate themselves by looking for humans and eating human leftovers. The study of Israeli fossils and genetics confirmed that the domestication period of dogs was about 6.5438+0 million years ago, which coincided with the agricultural revolution, and human beings changed from nomadic hunting to farming and settled life. Some scientists believe that wolves are attracted to the garbage dumps of these early settlements and feed on the leftovers of vegetables and cereal plants. (Continued/Click: [5] )[6]
Civilization influence
Loyal dog and eight male sculptures
Loyal dog and eight male sculptures
As the earliest domesticated livestock, the existence and evolution of dogs are inextricably linked with the development of human civilization. Westerners praise it with exquisite works of art and regard it as the most loyal guardian. However, the status of dogs in China has always been very low. This can be seen from the archaeological discoveries unearthed in China.
The most anticipated thing is that a large number of mammalian fossils were found in Zhoujiayoufang, Yushu County, Jilin Province, China, that is, the Late Pleistocene of Paleolithic Age, about 26,000 BC-0/000 BC. In addition to human fossils, there are also "semi-fossils" of domestic dog skulls. Although some people think it belongs to Pleistocene animal fossils, more experts think it is the remains of Holocene or modern animals. This remains of domestic dogs in the Paleolithic period can show that residents in Northeast China have begun to domesticate dogs. In other words, domestic dogs in Northeast China appeared in the late Paleolithic period, about 1 10,000 years ago. The primitive humans in Northeast China were Tunguska Mongols, so it is reasonable to think that the ancestors of Donghu, Rong, Di and Su Shen domesticated dogs, among which Rong was a famous dog-raising clan.
A batch of stamps and pictures of dogs.
A collection of stamp photos of dogs (20 photos)
It can be seen that Northeast China and Mongolia are the centers of domestic dog domestication in the late Paleolithic and early and middle Neolithic. In addition, in Anyang, Henan Province, Cishan, Hebei Province, Banpo, Xi 'an, Dawenkou, Shandong Province, Changzhou, Jiangsu Province and other places, the skeleton fossils of domestic dogs in the late Holocene were found, and it is certain that China is one of the centers of domestic dogs.
Feature-Physiology Editor
Dog's sense of smell
Dogs' olfactory sensitivity ranks first among all animals, and blind dogs can live like normal dogs with their noses. Dogs' acute sense of smell is mainly manifested in two aspects: first, they are sensitive to smells; The second is the ability to distinguish smells. The sensitivity will vary according to the kind of taste, which is about 1200 times that of human sense of smell. The dog's nose can distinguish about 2 million different smells, and it also has high analytical ability, and it can sniff out the smell it is looking for from many mixed smells. Dogs can perceive smells at the molecular level. For example, when 1 cubic centimeter contains 9000 butyric acid molecules, dogs can smell it, while in general, there are about 268× 10.e+ 16 molecules in the air per cubic centimeter. So the concentration of butyric acid felt by dogs is 3.36× 10.e- 17. When someone dilutes sulfuric acid by one millionth, dogs can still smell it, and their olfactory sensitivity to acidic substances is tens of thousands of times higher than that of people.
According to the European Lung Disease Foundation, lung cancer is the second leading cause of death in Europe. It was found that dogs trained in olfaction could sniff out 7 1 case from the breath samples of 100 patients with lung cancer, and the discrimination accuracy of non-lung cancer samples could reach 372/400. (Continued/Click: [1 1])
Dog's hearing
Dog's ear structure
Dog's ear structure
The auditory induction can reach1.2000 Hz, which is 6 times that of human beings. The farthest listening distance is about 400 times that of human beings. Dogs are also twice as able to distinguish the direction of sound as humans, and can distinguish 32 directions. It can be distinguished that the number of times the metronome vibrates per minute is 96 or 100, 133 or 144. For human passwords and simple languages, dogs can establish conditioned reflex according to the changes of tone and syllable.
Dogs can hear 40,000 cycles. The sound collected through the big ears vibrates the eardrum through the external auditory canal, even vibrates the ossicles of the middle ear, reaches the lymph of the inner ear, and then reaches the brain through the auditory nerve. Dogs can distinguish tiny or high-frequency sounds (ultrasonic waves). The ability to judge the sound source is also very strong. When a dog hears a sound, it can see and hear all directions with its eyes because of the sympathetic action of its ears and eyes. At night, even if you sleep, you should be highly alert and can clearly distinguish the sounds within the range of 1 km. In particular, we don't need to yell at the dog. Too much sound or audio is a kind of adversity stimulus for it, which will make it feel pain, fear or panic.
Dog's vision
Dog eye structure
Dog eye structure
Dogs' eyesight is only about three-quarters of that of humans, and among all animal species, dogs' eyesight is about medium. The dog can only see 25 degrees with one eye, so it can't see the nearest distance ahead. The lens of a dog's eyeball is relatively large and deformed like a horse's eyeball, so it is impossible to adjust the sense of distance. Twenty or thirty meters is probably its limit. Dogs have a special ability to detect moving objects; They can detect images that move 70 lines per second, while ordinary TV images move 60 lines per second. Dogs have better eyesight than people in dim light. Dogs are natural carnivores and live by hunting, so they also have considerable vision in the dark. Dogs' eyes can see short-wavelength colors. In addition, the dog's cornea is bigger, which allows more light to enter the eyes, so it is easier to see things in dim light. But in the darkness without light, dogs can't see.
The difference between human vision and dog vision lies in the reaction to light. The human eye reacts to the three primary colors (red, green and blue) that cause various colors. Dr DennisBrooks, associate professor of ophthalmology at the College of Veterinary Medicine, University of Florida, said that dog vision is different from human vision. Dogs can't tell colors like people, but they can see some colors. Dogs can distinguish different shades of blue, indigo and purple, but they are not particularly sensitive to high chroma colors such as red and green in the spectrum. Dr. Brooks' research shows that red is dark for dogs and green is white for dogs, so the green lawn is white for dogs. (continued/clicked: [12])
Dog's teeth
Dog's tooth structure
Dog's tooth structure
Dogs have short crowns. The crowns of the first and second maxillary incisors are three-pointed, with canine teeth in the middle and small peaks on both sides. The other front teeth have two small peaks, and the canine teeth are conical and extremely sharp, which is a powerful weapon for attack and self-defense. The front teeth are three-pointed, and the Japanese teeth are multi-pointed.
(1) Adult canine teeth (permanent teeth) consist of 42 incisors, canine teeth, premolars and molars.
⑵ Teeth types of puppies: 28 incisors, canine teeth and premolars, with premolars and molars missing 1 tooth.
Sweat glands of dogs
Skin structure of dogs
Skin structure of dogs
Canine animals, such as dogs and wolves, have underdeveloped sweat glands. Unlike people, they can't regulate their body temperature by sweating. Once their bodies get hot, it is difficult to lower their body temperature, so dogs are very afraid of heat.
Dogs also have exocrine sweat glands and apocrine sweat glands. Exocrine sweat glands used to regulate body temperature are only distributed on the meat pads of four claws, and there are few. It is impossible to lower the body temperature just by sweating on the paws. The apocrine glands that cause their body odor are distributed all over the body and have nothing to do with body temperature regulation.
As long as the dog feels a little hot, it will open its mouth and stick out its tongue to gasp, and it can secrete a lot of saliva instead of sweat. Dogs evaporate saliva to give off heat and lower their body temperature. They drool a lot and absorb heat through saliva evaporation to lower their body temperature. When the weather is hot, it is impossible to cool down smoothly by this method alone. So it is difficult for dogs to lower their body temperature. Especially pug, bulldog, poodle, chihuahua and other small dogs, because of their short respiratory organs, are not good at regulating body temperature, especially afraid of heat, so we should pay more attention. [ 13]
Dog's intestines and stomach
The digestive tract of dogs is shorter than that of herbivores, and the hydrochloric acid content in dogs' stomachs ranks first among domestic animals. In addition, the intestinal wall is thick, the absorption capacity is strong, and it is easy to digest meat food.
Unscramble sleep
Puppies and old dogs sleep longer, while puppies and strong dogs sleep shorter. Dogs are generally in a shallow sleep state, and they can wake up with a little movement, but there are also deep sleeps. When sleeping lightly, the dog is prone, with his head bent between his two front paws, often with one ear close to the ground. Dogs are not easy to wake up after a deep sleep, and sometimes they talk in their dreams, such as barking and moaning, accompanied by convulsions of limbs and shaking of their heads and ears. When you sleep, you often lie on your side and spread out all over. It looks cheerful.
Dogs are not easily awakened by acquaintances and owners when they sleep, but they are still sensitive to strange sounds. Dogs are often in a bad mood after being awakened from sleep, and they are very dissatisfied with the people who wake them up. Dogs that just wake up are blindfolded, and sometimes even their owners can't recognize them. So its dissatisfaction will sometimes be vented to its owner, such as barking at you. Don't wake it up because of boredom or mischief.
Healthy editing habits
Canine disease ranking
Canine diseases with high mortality: 1. Canine distemper, 2. Parvovirus, 3. Coronavirus.
Medical knowledge
Timely disinfection
If it is not a breeding dog, sterilization is recommended. The benefits of castrating dogs are as follows:
Avoid unnecessary duplication. If cats and dogs are not sterilized, the number of offspring will increase geometrically: if a pair of unsterilized cats and dogs are allowed to mate and reproduce, if two babies are born every year, the fifth year will theoretically increase to 12680. In many countries or regions, groups of wild cats or stray dogs are the result of castrated pets constantly multiplying outside. A large number of unwanted small animals were born into this world, and their fate must be very tragic.
Castrated pets are more docile and easier to raise; At the same time, it also avoids the pain of longing for love for pets and the possibility of getting lost from home because of looking for a partner. Uncastrated bitches are in estrus twice a year, and female cats are in estrus once every three months. In estrus, animals always try to go out and find a mate. Even if you keep it at home, you will be agitated, urinate and defecate everywhere to attract the opposite sex, and even damage furniture and articles, which will bring a lot of trouble. Male dogs don't fight and hurt each other because of jealousy.
Castration is beneficial to the health of pets, and reproductive diseases, such as breast cancer and uterine infection in women, testicular cancer and prostate disease in men, will no longer occur.
Is it cruel to castrate pets? Obviously not. Castration is a minor operation, especially for men. Veterinarians are carried out under anesthesia, and animals will not suffer and recover quickly.
Pregnant women and Toxoplasma gondii
(See Toxoplasma gondii for details) The main source of infection of Toxoplasma gondii is that people eat the meat of animals infected with Toxoplasma gondii by mistake, or by-products produced by Toxoplasma gondii animals (such as eggs, milk, cakes, ice cream, etc.). Other sources of infection are Toxoplasma gondii infection, mosquitoes, cockroaches, fruits and vegetables, grasslands, water and environment. Toxoplasma gondii infection, except cats as the ultimate host, other animals are only intermediate hosts. There are zygotes of Toxoplasma gondii in the feces of infected cats. It only takes 10-20 days for infected cats to excrete fertilized eggs. It takes 1-2 days or longer for zygotes to become infectious, so if you remove cat litter or cat excrement every day, you are not afraid of being infected. Dogs are the intermediate hosts of Toxoplasma gondii. Dogs can't produce infectious oocysts after contact with Toxoplasma gondii, and their feces and excreta are not contagious, so they can't be infected with Toxoplasma gondii simply by contact with dogs. If you don't eat dog meat, it won't be contagious.