Answer: Because fish scales are part of the fish's skin. Its body is very soft and very easy to be injured. It needs hard scales to protect it. Without scales, water will continue to penetrate into the body of freshwater fish, and the water in the body of saltwater fish will run out, and the fish will not survive. Therefore, fish have scales.
Answer: Because fish breathe with gills. At the same time, fish gills can only absorb oxygen dissolved in water, not oxygen in the air. Therefore, if the fish leaves the water, the fish's body cannot replenish oxygen, so the fish will die when it leaves the water.
Answer: Of course, because all animals need sleep and rest, otherwise they will become very weak or even die. Fish are no exception, but because they have no eyelids, when we see fish lying at the bottom of the fish tank with their eyes open and motionless, they are most likely sleeping.
Answer: Because there is a swim bladder in the fish's belly, and fish shrink or enlarge the swim bladder by contracting and relaxing muscles, and the air they inhale also changes. Since air is lighter than water, fish use the swim bladder to control sinking and floating.
Answer: Amphibians are animals between fish and reptiles, and have a dual life. Its characteristics are: First, the skin is thin and moist. It is composed of epidermis and dermis, contains most glands, and many blood vessels are gathered under the skin; second, the lungs of amphibians are sac-shaped, which are divided into small terminal air chambers. In addition, the heart of amphibians is divided into two atria and one ventricle. Blood circulation is divided into large and small circulation.
Answer: Because the body of birds is spindle-shaped and the bone marrow is full of air, birds have a large appetite. Digestion is also very fast, which makes birds very strong. In addition, birds have a well-developed nervous system, strong eyesight, and relatively light weight, etc. These characteristics are also important factors for birds to be good at flying.
Answer: Because there is a "biological clock" in the rooster's brain. According to scientific research, there is an endocrine organ called the pineal gland between the rooster's brain and cerebellum. The "biological clock" grows here. Because the pineal gland can secrete a kind of melanin at night, the rooster can remember the rules of light and dark and perform periodic crowing activities.
Answer: In daily life, donkeys have become good helpers for people. In some aspects, they are even much smarter than horses and other animals. In dangerous places and steep slopes, horses will break their legs while walking, but donkeys can run freely on the ground. Donkeys can accurately choose a convenient way when there is no road. It can also do some heavy physical work. So, donkeys are not stupid.
Answer: Because the pulp in the mouse's front teeth not only exists throughout life, but also keeps growing throughout life. In order to prevent the front teeth from growing too long and getting in the way, it is necessary to often bite hard objects to grind the front teeth so that it will not grow too long and affect eating.
Answer: The elephant's physique is getting bigger and bigger as the environment changes and the elephant's body adapts to the environment. The distance between the mouth and the grass growing on the ground is getting bigger and bigger, making it difficult to eat food on the ground. In addition, the body is not flexible enough, which makes it very inconvenient to move. In order to make up for these deficiencies, the elephant's nose gradually developed into what it is today.
Answer: When an ant finds some food, it will immediately return to the ant nest. It secretes a chemical substance while walking, leaving marks on the road. When it returns to the nest, it communicates information, and the ant relies on the smell of this chemical substance to move food.
Answer: Yes. Because the purpose of female mosquitoes sucking blood is to supplement nutrition and make their eggs mature. Most mosquito species cannot lay eggs without sucking blood. Male mosquitoes cannot bite people because of their underdeveloped mouthparts, and can only survive by relying on nectar, plant juice, etc.
Answer: Because human blood is easy to coagulate, mosquitoes will first inject saliva into the wound after inserting their mouths into human skin. This saliva can prevent blood from coagulating, so that they can suck human blood into their own stomachs. The mosquito's saliva contains irritants, and people react to this stimulation, so the wound is itchy and swollen.
Answer: Many animals use their tails to express their feelings. Dogs wag their tails to show that they are happy. Because they can't speak or do so many complex movements, they can only use the movement of their tails to express happiness.
Answer: Because animals have their own territory. When dogs are wild animals, they live in groups. Whenever people or other animals approach, the dogs will bark to inform their companions. Now people keep dogs at home, and dogs regard your home as their own home, so they will bark at strangers.
Answer: Horses have emotions like people, and they can only express their emotions through the movement of their ears. Therefore, horses' ears always shake
Answer: Because there is a substance (called endorphin) in the pig's brain that has an anesthetic effect. Since pigs are particularly afraid of heat, they will not move around, so pigs love to sleep.
Answer: When the weather is very hot in summer, the temperature of the ground is relatively low. Cats use this condition to make their bodies contact with the ground for heat exchange to regulate their body temperature. Therefore, cats are not afraid of heat.
Answer: Because ducks mainly live in water, their feet are backward, and their bodies are heavy in the front and light in the back. In order to maintain their balance when walking, they have to raise their heads and hold their chests high, so they wobble when they walk.
Answer: Because fish are cold-blooded animals, their body temperature is usually about the same as the water temperature, so even in summer, fish bodies are cool.
Answer: Because the upper part of a fish’s body is heavier than the lower part, when a fish dies, its back is down and its belly is up.
Answer: Because eels are amphibians, they breathe with gills in water and with their mouths on land. Therefore, eels can live out of water for a period of time.
Answer: Because before it rains, the air pressure in the sky is relatively low, and small flying insects fly very low at this time. In order to prey on these flying insects, swallows have to fly low.
Answer: Because the digestive organs of tigers cannot digest grass, and tigers like to eat active animals, so tigers don't eat grass.
Answer: Domestic chickens are the result of long-term breeding and domestication of ancient jungle fowl. Reptile eggs came first, and then chickens came out. However, although eggs are the beginning of a new life, they are not the origin of a new species. All organisms have evolved over a long period of time through environmental changes. Therefore, chickens are the result of long-term evolution in nature, and eggs are laid by chickens.
Answer: After the bird lands on a branch, it bends its legs. Due to the pressure of the body, the ligaments and muscles are stretched tightly, and the toes can firmly grasp the branch. Birds have a well-developed cerebellum and are good at adjusting their body balance, so that birds sleeping in trees do not sway back and forth.
Answer: Cats like to use their paws to "wash their faces" in order to remove dirt stuck on their whiskers. Only when the whiskers are kept clean can cats feel sensitive.
Answer: Snakes have many scales on their bodies, which is the outermost layer of armor on their bodies. Scales are not only used to protect the body, but also can be their "feet". When a snake crawls forward, its body will be in an S shape. And each scale outside the S shape will curl up to help the snake grasp the uneven road surface when it moves forward. These scales cooperate with the snake's muscles and can push the body forward to crawl, so snakes can walk without feet!
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