Science common sense primary school

1. Rabbits beat the ground with their legs to transmit information, mostly with their hind legs, which is a way for them to express their feelings to female rabbits. 2. The biggest monkey in the world is a baboon and the smallest monkey is a bonobo. 3. The real name of "Four Elephants" is Elk, which is a rare animal in China. 4. Why does sorbet get angry? The reason why sorbet bubbles is because there is a lot of invisible water vapor in the outside air. When it comes to cold sorbet, it will liquefy into droplets when it is cold. It seems that the sorbet is bubbling.

5. Why do sunflowers always face the sun? Sunflower stems contain a wonderful auxin. This auxin is very afraid of light.

When it is illuminated, it will go to the backlight side, and the cells on the backlight side will multiply rapidly. Therefore, the backlit side will grow faster than the bright side, which will bend the sunflower to light. 6. Why do cicadas shed their skin? Cicada's shell (exoskeleton) is hard and can't expand with the growth of cicada. When the cicada grows to a certain stage, the cicada's exoskeleton restricts its growth, and the cicada loses its original exoskeleton, which is cicada slough.

7. How do bees make honey? First, the bees spit the sweet juice of the flowers they picked into an empty hive. At night, they suck sweet juice into their honey stomachs to make it, and then spit it out and swallow it. It takes 100~240 times to make sweet honey. 8. Why do the stars twinkle? We see the stars shining, not because the luminosity of the stars has changed, but because of the occlusion of the atmosphere.

The atmosphere is between us and the stars. When starlight passes through the atmosphere, it will be affected by the density and thickness of the atmosphere. The atmosphere is not absolutely transparent, and its transparency will change according to its density.

So when we look at the stars through it on the ground, we will see that the stars seem to be flashing. 9. Why do people yawn? When we feel tired, a lot of carbon dioxide has been produced in our bodies.

When there is too much carbon dioxide, oxygen must be supplemented to balance the needs of the body. Because these residual carbon dioxide will affect our body's functional activities, then the body will send out a protective reaction, so we yawn.

Yawning is a deep breathing action, which will let us breathe in more oxygen and expel more carbon dioxide than usual, and it can also eliminate fatigue. 10, why can a snake walk without feet? Snakes have many scales, which are the outermost armor on their bodies.

Scales are not only used to protect the body, but also to be their "feet". When a snake crawls forward, its body will be S-shaped.

Every scale outside the S-shape will tilt upward to help the snake catch the uneven road when it moves forward. These scales cooperate with the snake's muscles and can push the body forward, so the snake can walk without feet! 1 1. Why does hair turn white when people get old? There is a substance called melanin in our hair. The more melanin, the darker our hair will be.

Without melanin, hair will turn yellow or white. When human beings reach old age, various functions of the body will gradually decline, and the formation of pigments will be less and less, so the hair will gradually turn white! 12. Why do fireflies glow? Fireflies emit light because there is a luminous body at the end of their abdomen, which is filled with a lot of phosphorus-containing luminescent substances and luminescent enzymes, so that fireflies can emit flashing light.

The purpose of fireflies is not only lighting, but also courtship, vigilance and trapping. This is also a communication tool for them. Different kinds of fireflies emit light in different ways, frequencies and colors, so they can convey different information.

13. Why do you growl when you are hungry? When you are hungry, you will purr. This is because the food you have eaten before has almost been digested. Although the stomach is empty, the gastric juice in the stomach will continue to secrete. At this time, the contraction of the stomach will gradually expand, and the liquid and gas inside will be stirred up and purr.

Don't be embarrassed by your stomach growling next time! Because this is a normal physiological action. 14. Why can't ostriches fly? A giant ostrich, but they can't fly into the sky! This is not because their wings are useless, but because their feathers are too soft and their wings are too small to fly at all.

In addition, the ostrich's muscles are underdeveloped and its sternum is flat, which is not conducive to flying. Ostriches live in Africa. Because they have lived in desert areas for a long time, their bodies gradually evolved into what they are now in order to adapt to the environment.

15. Why can't the food in cans go bad easily? Lunch meat, black bean shad, tomato sauce beans.

They are all delicious canned food, which can be preserved for a long time without deterioration. This is because the can is sealed, so bacteria can't enter.

When people make canned food, they pump all the air out of the canned food and then seal it. In the absence of air, even if the food inside is contaminated with a little bacteria, they can't survive or reproduce! 16. Why does the baby cry all the time when it is born? Babies cry when they are born, not because they are unhappy, but because they are taking the first breath of air! When babies leave their mother's body and are born, the first breath of air will rush to their throats, violently impact the vocal cords, make them vibrate, and then make a sound similar to crying.

17. Why do lizards keep bouncing backwards when their tails are broken? In order to protect themselves, many lizards also protect their eyes and ears; When some lizards are attacked, their tails will be broken due to the severe contraction of their muscles. Because there are still some nerves alive in the broken tail, it will keep bouncing, thus distracting the enemy and running away.

Don't think that their lives will end like this. In fact, it only takes a few months, and their tails will grow back and continue to live. 18. Why is the squirrel's tail so big? Don't look at the relaxed mouse tail! When the squirrel jumps around the tree, its tail plays a great role.

It can keep balance when the squirrel jumps to the tree to avoid falling and being injured. In addition, this big tail can play a more protective role in winter, tightly surrounding the squirrel's body, which is convenient and practical.

19, why can't a human thumb have one or three knots? The average person has five fingers, the length of which.

2. What little scientific knowledge do the pupils around you have?

1. Why do the stars twinkle? We see the stars shining, not because the luminosity of the stars has changed, but because of the occlusion of the atmosphere.

The atmosphere is between us and the stars. When starlight passes through the atmosphere, it will be affected by the density and thickness of the atmosphere. The atmosphere is not absolutely transparent, and its transparency will change according to its density.

So when we look at the stars through it on the ground, we will see that the stars seem to be flashing. 2. Why do people yawn? When we feel tired, a lot of carbon dioxide has been produced in our bodies.

When there is too much carbon dioxide, oxygen must be supplemented to balance the needs of the body. Because these residual carbon dioxide will affect our body's functional activities, then the body will send out a protective reaction, so we yawn.

Yawning is a deep breathing action, which will let us breathe in more oxygen and expel more carbon dioxide than usual, and it can also eliminate fatigue. 3. Why can snakes walk without feet? Snakes have many scales, which are the outermost armor on their bodies.

Scales are not only used to protect the body, but also to be their "feet". When a snake crawls forward, its body will be S-shaped.

Every scale outside the S-shape will tilt upward to help the snake catch the uneven road when it moves forward. These scales cooperate with the snake's muscles and can push the body forward, so the snake can walk without feet! 4. Why do sunflowers always bloom towards the sun? There is a substance called "auxin" in the stem under the sunflower disk.

This substance has the function of accelerating replication, but it is anti-optical, and it will run to the backlight side whenever it encounters light. So when the sun rises, the stem of the sunflower immediately hides to the side of the backlight, as if the whole plant is bent in the direction of the sun.

5. Why does hair turn white when people are old? There is a substance called melanin in our hair. The more melanin, the darker our hair will be. Without melanin, hair will turn yellow or white.

When human beings reach old age, various functions of the body will gradually decline, and the formation of pigments will be less and less, so the hair will gradually turn white! 6. Why do fireflies glow? Fireflies emit light because there is a luminous body at the end of their abdomen, which is filled with a lot of phosphorus-containing luminescent substances and luminescent enzymes, so that fireflies can emit flashing light. The purpose of fireflies is not only lighting, but also courtship, vigilance and trapping.

This is also a communication tool for them. Different kinds of fireflies emit light in different ways, frequencies and colors, so they can convey different information. 7. Why do you growl when you are hungry? When you are hungry, you will purr. This is because the food you have eaten before has almost been digested. Although the stomach is empty, the gastric juice in the stomach will continue to secrete.

At this time, the contraction of the stomach will gradually expand, and the liquid and gas inside will be stirred up and purr. Don't be embarrassed by your stomach growling next time! Because this is a normal physiological action.

8. Why can't ostriches fly? A giant ostrich, but they can't fly into the sky! This is not because their wings are useless, but because their feathers are too soft and their wings are too small to fly at all. In addition, the ostrich's muscles are underdeveloped and its sternum is flat, which is not conducive to flying.

Ostriches live in Africa. Because they have lived in desert areas for a long time, their bodies gradually evolved into what they are now in order to adapt to the environment. 9. Why can't it go bad easily? Lunch meat, black bean shad, tomato sauce beans.

They are all delicious canned food, which can be preserved for a long time without deterioration.

This is because the can is sealed, so bacteria can't enter. When people make canned food, they pump all the air out of the canned food and then seal it.

In the absence of air, even if the food inside is contaminated with a little bacteria, they can't survive or reproduce! 10. Why does the baby cry all the time when it is born? Babies cry when they are born, not because they are unhappy, but because they are taking the first breath of air! When babies leave their mother's body and are born, the first breath of air will rush to their throats, violently impact the vocal cords, make them vibrate, and then make a sound similar to crying. 1 1. Why do lizards keep bouncing up after their tails are broken? In order to protect themselves, many lizards also protect their eyes and ears; When some lizards are attacked, their tails will be broken due to the severe contraction of their muscles.

Because there are still some nerves alive in the broken tail, it will keep bouncing, thus distracting the enemy and running away. Don't think that their lives will end like this. In fact, it only takes a few months, and their tails will grow back and continue to live.

3. All knowledge points of primary school science

Science 1 Unit 1 In the game, an object has a downward force, which is gravity.

2. For cars powered by rubber bands, the more times the rubber bands are wound, the faster they travel and the farther they travel. The fewer times the rubber band is wound, the slower the driving speed and the closer the driving distance. 3. When rubber bands, springs and other objects are subjected to external force, their shapes are easy to change. When their shape changes, they will generate a force to restore their original shape. This force is called elasticity.

4. Elastic bands of clothes and trousers, wallets, bows and arrows, tensioners and various springs all use the elasticity of objects. When the gas in the balloon is ejected, it will produce a thrust opposite to the ejection direction. This force is called recoil.

Jet planes and rockets are moved by recoil generated by jet engines. 6. To make delicate objects move, we must exert force on them; To make an object move faster, you must exert more force on it.

7. In science and technology, the Newton-based unit, referred to as "cow" for short, is uniformly stipulated and represented by "n". 1 Newton is approximately equal to 100 gram force.

8. Attention should be paid when using the spring dynamometer to measure gravity: (1) Pick up the dynamometer and check whether the pointer is in the "0" position first; (2) When reading, the line of sight is flush with the pointer; (3) The measured force shall not exceed the maximum value marked on the dynamometer scale. 9. When an object moves on the surface of another object, the contact surface of the two objects will be rubbed, and the moving object will be subjected to a force that hinders the movement. This force is called friction.

10, we use a dynamometer to pull an object in the horizontal direction, and the force that just makes the object move is the friction it receives. 1 1, the contact surface between objects is smooth and the friction is small; Roughness of the contact surface between objects will increase friction.

The heavier the object, the greater the friction when moving; The lighter the object, the less friction. 12. An object moves on the surface of another object in two ways: sliding and rolling.

Sliding friction is much larger than rolling friction. 13. When an object moves on the surface of another object, there will always be friction.

14, where the bicycle needs to be rubbed: there are patterns on the front and rear tires, pedal surfaces, brake rubber and handlebars; Where no friction is needed: front axle, middle axle, rear axle, pedal axle, large and small gears and chains. 15. Design features of the racing car: (1) The tires are very wide, which can increase friction and avoid slipping; (2) Design a powerful engine; (3) The center of gravity of the car body is very low, and the wheel spacing is wide, which can make the driving smooth; (4) Design a streamlined body to minimize resistance.

16. Both push and pull will generate force, and both push and pull will make the object move. Thrust and tension also have magnitude and direction.

When we push or pull an object on the ground, we feel laborious because there is friction between the object and the ground. 17. The balance is made according to the balance principle of the lever ruler.

Balance is an instrument to measure the quality of goods. When weighing the goods, put the weighed goods on the left plate and the weights on the right plate. If the weights are properly placed, the balance will be balanced left and right. If it is not balanced, adjust the travel code to make it balanced.

18. The weights of the balance are: 1g, 2g, 2g, 5g, 10g, 20g, 50g, 100g * * 9. When carrying heavy objects, do not hold them directly with your hands, but with your hands. At the end of weighing, the tray should stop swinging as soon as possible.

19. The compass is made according to the characteristic that magnets can indicate north and south. Compass is one of the four great inventions in ancient China.

One end of the magnet tube is called the South Pole, which is denoted by S, while the north end is called the North Pole, which is denoted by N ... the sun and time. Objects that can emit light by themselves, such as electric lights, are called light sources.

2. Like this, the shadows of objects illuminated from different sides are called projections. 3. Shadow must be composed of light source, screen and shelter.

4. The length of the shadow is related to the position and angle of the light source. 5. The size of the shadow is related to the distance from the light source to the object.

6. The shape of the shadow is related to the side of the illuminated object. 7. People in ancient times used sundials to record time.

Xiao Ming found that the shadow of the big tree faces west and the sun is in the east. 9. Light travels in a straight line at the speed of 300,000 kilometers per second.

10. When the light hits the mirror, it will change its propagation direction and be reflected back. This phenomenon is called light reflection, and light travels in a straight line. 1 1. There are forehead mirrors and reflectors that use light reflection.

12. The surface temperature of the sun is more than 6000 degrees Celsius, and the internal temperature is more than 20 million degrees Celsius. 13. Black rough objects have the strongest heat absorption capacity.

14. The vertical temperature rise of objects and sunlight is fast. 15. People use solar energy: solar cookers, solar panels, lighting the Olympic flame and solar water heaters.

16. There are concave mirror and convex lens for focusing light. 17. Pupils dilate under weak light and contract under light intensity.

18 We can use regular or rhythmic activities to estimate time, such as (counting heartbeat) and (tapping the table rhythmically). But according to our estimation, we can't know the time accurately.

19, time is passing at a constant speed. Usually, we think that the speed of time is how we feel at work. 20. Before the invention of the clock, people measured the time according to the position of the sun in the sky, making it at sunrise and resting at sunset.

2 1. In ancient times, we divided a day (day and night) into twelve hours, and each hour is now two hours. In ancient Egypt, a day was divided into (24) hours, (12) days and (12) nights according to the intersection of 36 constellations in the sky in a year. 22, (sundial) is to use the change of the position of the sun in the sky, so that the shadow length and position of objects on the ground change with time.

23. In a device, water can continuously flow downwards at a steady speed. According to this feature, humans made (water clocks) to time. 24. There are two kinds of ancient water clocks: water-receiving type and water-discharging type, both of which are made according to the change of water quantity.

25. In the dripping experiment, if the water flows downwards, the flow rate of the water is (not fixed), and with the decrease of the water volume, the speed becomes (slow). The less water in the container, the slower the water flows.

26. The time required for each swing of the same simple pendulum is (the same); According to the isochronism of a simple pendulum, people made pendulum clocks to reduce the measurement error of time. 27, placed in the middle.

4. Primary school science knowledge How to keep animals and plants warm when the cold winter comes?

Animals have ways to keep out the cold, and people will add clothes to keep out the cold. What about the animals in the zoo? It turns out that there is a clever way to keep out the cold. Let's go and have a look. People only hate wearing less clothes these two days, and some small animals in the zoo are also afraid of the cold. The rabbit's cage is covered with canvas to keep out the cold, and waterfowl don't go into the water. The kitten curled up on the haystack, the horse covered with a quilt, and even the tortoise hid under the haystack. Small animals that are afraid of the cold all got into the breeder. There are no signs of monkeys these two days. If you look carefully, they are all huddled in the lee of Monkey Mountain, hugging each other for warmth. Three strong lions still "live on it", but if the temperature continues to drop and it rains, they have to be boarded to prevent them from sleeping directly on the concrete floor and catching cold. Even this camel is the most comfortable in the cold wind. Compared with the temperature of tens of degrees below zero in the desert, this kind of weather is a piece of cake. The temperature has plummeted in these two days. They cover the cages of small animals with thick straw to shield them from the cold wind, enrich their recipes, increase energy-based foods such as wheat and enhance their ability to resist cold weather. In winter, plants that help plants keep out the cold are alive, but in the face of severe cold, some plants often turn yellow and die because they can't adapt. What are the simple, economical and quick ways to prevent cold? To this end, the reporter invited Lin from Wantong Garden Company to teach you a trick. Method 1: "Dress" to prevent cold. "Dresses" were originally wrapped in linen, but never in plastic bags. Plants are alive and need sunshine and air. Hemp is the best "clothing material", especially for newly planted plants, which have few roots and weak vitality. At the same time, they need careful care. Covering the whole factory. The black net is about one or two yuan/meter. But many families don't like black, so they can choose green net. However, the price will be twice as expensive. These products will be sold in Guangzhou Lingnan flower and other wholesale markets. Method 2: Reduce the "burden" Many people think that it is enough to "add clothes" to plants in winter. As we all know, plants should reduce their burden. Lin said that the more leaves there are, the greater the area of plants that are frozen. Prune plants properly before the cold current comes, but pruning is learned. The tools used should not be too sloppy, and the stationery scissors should not be used casually. It is suggested to use "big flower scissors", which are sold in Fangcunyue and the world of flowers, birds, fish and insects, ranging from 20- 100 yuan. Good scissors are durable and not easily deformed. It is best to choose products with hard blades, thick blades and strong handles. Method 3: Move in time. In winter, the north wind is particularly strong, and the tuyere position should avoid plants. If possible, move some potted plants indoors, away from windows. But don't let plants spend the whole winter indoors. It is suggested that they be basked in the sun when the weather is fine. Method 4: Simple heat preservation. The storage box with inner frame used by ordinary families can be used as a greenhouse for plants. Put a proper amount of small potted plants, add water not exceeding the height of the inner frame, and cover it to make a simple incubator. Because there is steam circulation in the "secret room", there is no need to water the plants alone at ordinary times. Tips for heat preservation: Which plants are more afraid of cold? Plants from tropical areas are more afraid of cold, such as pueraria lobata, indigo leaf, meconopsis prostrate, arrowroot, rich tree, black nightshade, old sunflower, Zhu Jin and so on.

5. Primary school science knowledge:

The trunk of a dog is supported by its forelimbs and hind limbs, which makes it higher from the ground and is conducive to running and jumping. There are heart and lung organs in the back and chest, digestive organs and partial excretory reproductive organs in the waist and abdomen. The pelvis below the recommended position (including buttocks, pelvis, tail, etc.). ), including the digestive organs and the posterior segment of excreting reproductive organs. There are usually 4-5 pairs under the chest and abdomen. The first pair is in the chest, and the other 3-4 pairs are arranged at a certain distance in the abdomen. The dog's abdomen is very compact and contracts upward, commonly known as the upper abdomen, which is conducive to running, jumping and chasing.

There are two little white pigs in my family. They are all white, and their big ears are like two powerful fans, flapping up and down; Long nose, a pair of round nostrils, like two small caves; There is a big mouth hidden under the nose. If you don't look carefully, you won't find a mouth under your nose. There are a pair of unpredictable little eyes and wrinkles on the nose, which really doesn't look good.

The newborn kitten, with closed eyes, thin voice and naked body, looks like a crawling meatball.

After the full moon, all the villi grow together. Some collars are white, the limbs are covered with white hair, the back is black and gray, and the tail is gray and black; Some people wear a dark coat from beginning to end, but the soles of their feet are white. People say it is an excellent variety, called "black clouds cover snow"; Some are yellow and tiger-patterned, and people have given it a good name "gold does not change"; There is also a kind of white hair and black hair tail, which is called "dragging a gun in the snow" A full-moon cat can't walk without milk.

This crab is half the size of my palm. Except for its abdomen, its shell is turquoise, as if covered with a green gown. Its hard body is like wearing a suit of armor. Look, those thick crab claws seem to pose as "fists". Ah, those eight steps, each of which consists of seven bars, are like eight slender "seven-section sticks". One section of the tip is claw-shaped, and the other sections are flat strips or short columns. There are still some fine hairs on the feet, which adds a bit of momentum to this imposing appearance.

What a coincidence! The students waved their flower handkerchiefs in the air, and the peacock really opened its screen. I saw a peacock wagging its tail loudly. That beautiful tail is like a colorful fan in the fairy's hand, spreading slowly, and like a bright pearl sprinkled on it, which is very beautiful. When the tail is open, it is bright and dazzling. Those peach-shaped patterns, the outer ring is gray, the second ring is light blue, and the last ring is sapphire blue with a little dark red, which is really beautiful. It can be proud, hold its head high, hold its chest out, turn back and forth and show off its beauty.

6. Primary school students' scientific knowledge is very simple.

2. If bitten by mosquitoes, you can apply soapy water on it to stop itching. Because the mosquito bites will spit an acid there, and soapy water is alkaline, so the acid-base combination. 1. Why do the stars twinkle? We see the stars shining, not because the luminosity of the stars has changed, but because of the occlusion of the atmosphere.

The atmosphere is between us and the stars. When starlight passes through the atmosphere, it will be affected by the density and thickness of the atmosphere. The atmosphere is not absolutely transparent, and its transparency will change according to its density.

So when we look at the stars through it on the ground, we will see that the stars seem to be flashing. 2. Why do people yawn? When we feel tired, a lot of carbon dioxide has been produced in our bodies.

When there is too much carbon dioxide, oxygen must be supplemented to balance the needs of the body. Because these residual carbon dioxide will affect our body's functional activities, then the body will send out a protective reaction, so we yawn.

Yawning is a deep breathing action, which will let us breathe in more oxygen and expel more carbon dioxide than usual, and it can also eliminate fatigue. 3. Why can snakes walk without feet? Snakes have many scales, which are the outermost armor on their bodies.

Scales are not only used to protect the body, but also to be their "feet". When a snake crawls forward, its body will be S-shaped.

Every scale outside the S-shape will tilt upward to help the snake catch the uneven road when it moves forward. These scales cooperate with the snake's muscles and can push the body forward, so the snake can walk without feet! 4. Why do sunflowers always bloom towards the sun? There is a substance called "auxin" in the stem under the sunflower disk.

This substance has the function of accelerating replication, but it is anti-optical, and it will run to the backlight side whenever it encounters light. So when the sun rises, the stem of the sunflower immediately hides to the side of the backlight, as if the whole plant is bent in the direction of the sun.

5. Why does hair turn white when people are old? There is a substance called melanin in our hair. The more melanin, the darker our hair will be. Without melanin, hair will turn yellow or white.

When human beings reach old age, various functions of the body will gradually decline, and the formation of pigments will be less and less, so the hair will gradually turn white! 6. Why do fireflies glow? Fireflies emit light because there is a luminous body at the end of their abdomen, which is filled with a lot of phosphorus-containing luminescent substances and luminescent enzymes, so that fireflies can emit flashing light. The purpose of fireflies is not only lighting, but also courtship, vigilance and trapping.

This is also a communication tool for them. Different kinds of fireflies emit light in different ways, frequencies and colors, so they can convey different information. 7. Why do you growl when you are hungry? When you are hungry, you will purr. This is because the food you have eaten before has almost been digested. Although the stomach is empty, the gastric juice in the stomach will continue to secrete.

At this time, the contraction of the stomach will gradually expand, and the liquid and gas inside will be stirred up and purr. Don't be embarrassed by your stomach growling next time! Because this is a normal physiological action.

8. Why can't ostriches fly? A giant ostrich, but they can't fly into the sky! This is not because their wings are useless, but because their feathers are too soft and their wings are too small to fly at all. In addition, the ostrich's muscles are underdeveloped and its sternum is flat, which is not conducive to flying.

Ostriches live in Africa. Because they have lived in desert areas for a long time, their bodies gradually evolved into what they are now in order to adapt to the environment. 9. Why can't it go bad easily? Lunch meat, black bean shad, tomato sauce beans.

They are all delicious canned food, which can be preserved for a long time without deterioration.

This is because the can is sealed, so bacteria can't enter. When people make canned food, they pump all the air out of the canned food and then seal it.

In the absence of air, even if the food inside is contaminated with a little bacteria, they can't survive or reproduce! 10. Why does the baby cry all the time when it is born? Babies cry when they are born, not because they are unhappy, but because they are taking the first breath of air! When babies leave their mother's body and are born, the first breath of air will rush to their throats, violently impact the vocal cords, make them vibrate, and then make a sound similar to crying. 1 1. Why do lizards keep bouncing up after their tails are broken? In order to protect themselves, many lizards also protect their eyes and ears; When some lizards are attacked, their tails will be broken due to the severe contraction of their muscles.

Because there are still some nerves alive in the broken tail, it will keep bouncing, thus distracting the enemy and running away. Don't think that their lives will end like this. In fact, it only takes a few months, and their tails will grow back and continue to live.

12. Why is the squirrel's tail so big? Don't look at the relaxed mouse tail! When the squirrel jumps around the tree, its tail plays a great role. It can keep balance when the squirrel jumps to the tree to avoid falling and being injured.

In addition, this big tail can play a more protective role in winter, tightly surrounding the squirrel's body, which is convenient and practical. 13. Why can't a person have one or three thumbs? The average person has five fingers, each with a different length.

However, does anyone realize that besides the thumb, other fingers also have three sections, while the thumb alone has only two sections? It turns out that the number of joints is just the same as the other four fingers. If it is three knots, the thumb will appear weak, so that it can't lift heavy objects; If there is only one section, it can't grasp things freely with the other four fingers! 14. Why don't you scratch yourself? When others scratch ourselves, we feel itchy and laugh nonstop; However, when we scratch ourselves, we not only don't laugh, but also don't itch.

Based on our psychological preparation, the brain will send out a message that there is no danger, and the nerves will relax, so that they will not laugh and itch! 15. Why are most seawater blue and green? Looking at the sea, you often find the sea.