1. Only female mosquitoes bite: the purpose of female mosquitoes' blood feeding is to supplement nutrition and make their eggs mature. Most kinds of mosquitoes can't lay eggs without sucking blood. Male mosquitoes can't bite people because their mouthparts are underdeveloped, and they can only rely on nectar and plant juice to maintain their lives.

2. Why can't a person's thumb have one or three knots? 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! Why fish have scales: Because fish scales are a part of fish skin, its body is soft and easy to get hurt, so it needs hard fish scales to protect it. If there is no fish scale, water will continue to penetrate into freshwater fish, and the water in marine fish will escape, so the fish can't live, so the fish has fish scales.

3. Why is the sea mostly blue and green? Looking at the sea, it is often found that the sea water is blue-green. However, when you pick up the sea water, you can only see it as transparent and colorless as old water. It turns out that the seawater itself is not much different from the water we touch every day, and it is also transparent. The green we see is actually a phenomenon caused by the ability of seawater to absorb light. Only green light can be absorbed and reflected by seawater; When the seawater is deep, the green light is also absorbed, and the seawater looks blue.

4. Why do you get goose bumps? There is hair on the surface of our skin, and there is a vertical hair muscle under each pore. When we are exposed to nerves (such as anger, fear, cold, etc.) ), the temperature of our body will drop, and the vertical hair muscles will contract, making the hair stand up and form goose bumps. In addition to keeping warm, this physiological system can make animals look bigger than they really are, thus scaring off enemies. The secret of bird flight: Because the bird's body is spindle-shaped, its bone marrow is full of air, and it eats a lot. Digestion is also particularly fast, which makes the bird's physical strength particularly strong. In addition, the developed nervous system, strong eyesight and relatively light weight of birds are also important factors for birds to be good at flying.

5. Why not tickle yourself? When others scratch ourselves, we will feel itchy and laugh constantly; 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!

6. Why do whales spray water? A whale is a mammal, but its nose has no shell, and its nostrils grow on the top of its head. Living in water and breathing with the lungs can store a lot of air at a time, and you don't need to breathe on the surface often. But when it breathes to the surface, it breathes through its nose. When it breathes, the huge sound waves emitted by the sea water are caused by pressure.

7. Why do most household appliances such as electric fans, washing machines and refrigerators use three-wire plugs? What is the difference between a three-wire plug and a three-phase plug? Three-phase electrical appliances refer to three different live wires, and the voltage between each two wires is 380 volts. They are generally used in power systems and are more common in industrial electricity consumption. Single-phase power supply is generally used in household appliances, and its three wires are live wire, neutral wire and ground wire. The voltage between the live wire and the neutral wire is 220 volts, so this is not three-phase electricity, and its plug socket is not a three-phase plug socket. The grounding wire is to ensure safety.

8. Why do leaves change color? The reason why leaves change color is related to the chemical substance chlorophyll. When autumn comes, the days are shorter and the temperature is lower than that in summer, so the leaves stop producing chlorophyll, and the remaining nutrients are transported to the trunk and roots for storage. Leaves lack green chlorophyll and other chemical pigments appear at the same time, so we often see yellow and brown leaves.

9. Why are there fallen leaves? It's fall here. Leaves evaporate more water than in summer, but roots absorb less water than in summer. In order to reduce the water loss of trees, stem cells began to form separation layers. When the nutrients leave the leaves completely, the separation layer separates the leaves from the trunk and leaves fall off.

10. 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!

1 1. Was the seahorse born in dad's stomach? Almost all animals are females, but the hippocampus is different. It's male. On the belly of the male hippocampus, there is an incubator similar to a kangaroo "pouch", and the female hippocampus will discharge the eggs into the incubator of the male hippocampus. Since then, the male hippocampus has assumed the responsibility of pregnancy. In about three weeks, the little sea horse will pop out of his father's body. Hippocampus was born in dad's belly? Almost all animals are females, but the hippocampus is different. It's male. On the belly of the male hippocampus, there is an incubator similar to a kangaroo "pouch", and the female hippocampus will discharge the eggs into the incubator of the male hippocampus. Since then, the male hippocampus has assumed the responsibility of pregnancy. In about three weeks, the little sea horse will pop out of his father's body.

2. Excerpt good high-tech clips

1: The sound of waves beating against rocks and beaches is endless.

The water spray is almost like a white line, rushing from a distance, slamming on the shore, making a rhythmic splash, then bubbling and disappearing between the sand and stones. A row of waves followed ...-Qin Mu's "Gold Coast" II: The wind caressed the satin chest of the sea, and the sun warmed it with its own warm light, while the sea gasped like a dream under the gentle power of these caresses, filling the boiling air with evaporated salt.

The pale green waves rushed to the yellow sand, splashing white foam, dissipating gently on the hot beach and wetting the beach. -[Su] Gorky's Malhua 3: In front of us is a magnificent and quiet sea with endless blue and smooth marble.

Looking around, the sea is connected with the light blue sky: ripples reflect the melting sun and present a piece of flame. The mountains in the distance are looming in the morning fog.

Lazy waves crept affectionately to their feet and licked the golden beach on the coast. -[Su] ostrovsky's How Steel was Tempered 4: The moon has risen very high.

The sky and the sea are also clearer and more lovely. The breeze blew over the silver sea, bringing the fragrance of Mayflower to the surrounding islands.

On the silver sea, there is a particularly bright silver belt that goes straight to the place where the moon rises, reminding people that this is a road to the moon palace. This road is like a brilliant piece of broken silver.

Our ship, along this broken silver paved road, flies forward towards the moon. -Jun Qing's "Haiyan" 5: The drizzle in mid-April, shining and falling, made the air surprisingly cool.

The young leaves are still small, but there are some green leaves everywhere. Shy Chunyang only peeped out some soft light from the thin clouds: the figures and shadows on the ground were very weak.

The wild peach blossoms bloom very early, and the faint pink is swaying in the wind and rain, like a weak village girl, dressed simply and beautifully. -Lao She's "Two Horses" 6: Spring.

The yellow leaves turned green. New green leaves have grown on the dead branches.

The sunshine smiles gently at everyone, the birds are singing and flying. Flowers are blooming, red flowers, white flowers and purple flowers.

The stars are shining, red, yellow and white. Blue sky, free wind, dreamlike love.

Everyone has spring. No matter you or me, everyone can have laughter, love and intoxication in spring.

-Ba Jin's "Autumn in Spring" 7: Spring is in Wanshan Huai, and it is even more venting. The peach blossoms there are still in full bloom, and the drifting thin clouds fly from one peak to another, sometimes stopping for a while, in order to block the sun and let the flowers and plants on the ground avoid the threat of fire under its shade.

The shade under the rock and the edge of the mountain stream are covered with ferns and other ferns. The green is dotted with red, yellow, blue and purple flowers.

The lark in the sky and the oriole in the forest are all tongue-tied. The breeze gathers their voices and distributes them to all kinds of creatures in the mountains who have no ears.

Peach blossom listened with ecstasy, and couldn't help but shed a few drops of pink tears, which condensed on the ground one by one. Grass and flowers are drunk, and they fall and get up with the beat of the sound, so there is no time to calm down.

-Xu Dishan's "Spring Woods" 8: It was March day, and the sky outside the city was unusually high and clear. The fields are crisp and soft, and the grass is tender. Among them, dandelion is a little yellowish, which makes people feel a little rippling.

Willow trees from a distance are smoky green and dizzy like a dream. When I looked closer, the branches had no leaves, and the veins under the skin were clearly green. There are many pedestrians on the road, some by car, some looking for something; Some carry burdens, or buy and sell.

Spring has come quietly, and only they are so carefree and intoxicated. Only they have won the wonderful taste of spring.

-Jia Pingwa tastes tea.

3. Notes on scientific knowledge

Notes on gourmet travel

By studying Food Travel, I got a preliminary understanding of how food travels, basically as follows:

1. In the mouth, food is preliminarily decomposed into maltose by salivary enzymes and crushed.

2. Then I went to the stomach, where I digested 1 part of the water and alcohol and converted maltose into glucose, but the fat was not decomposed (that is, the food was decomposed into mud, such as what some people spit out after being drunk), and the food was mainly muddy for simple absorption.

3. Then we reach the small intestine, which is the most important digestive process in the small intestine. The small intestine is thin and long, with many villous protrusions inside, so that we can fully absorb water, fat, glucose and various inorganic salts (vitamins) to play the main role of digestion.

4. Then we went to the large intestine. Recently, scientists also found that the large intestine can absorb dietary fiber left in food. Dietary fiber has some functions of promoting digestion and other functions (please wait for scientists to find out in step 1). The substances in feces are food residues and undigested substances. The large intestine mainly plays the role of storing feces.

Finally, food residue will be excreted.

In the future, I will study harder and master more scientific skills.

Experience of Reading "The Extinction of Dinosaurs"

People are still studying the reasons for the extinction of dinosaurs. For a long time, the most authoritative view is that the extinction of dinosaurs was related to a big meteorite 65 million years ago. In addition to the "meteorite impact theory", the main viewpoints about the extinction of dinosaurs are:

First, the theory of climate change. Second, the theory of species struggle. Third, the theory of continental drift. Fourth, the theory of geomagnetic variation. Five, angiosperm poisoning theory. Sixth, the theory of acid rain.

The complete extinction of dinosaurs is a strange thing. Fortunately, we have now acquired some precious dinosaur fossils, which enables scientists to carry out their research work. We hope that this mystery will be solved in the near future. At the same time, we should know that any living thing has to go through the process of production, prosperity and extinction. This is a natural law and will not change because that species is huge and powerful. Dinosaurs went extinct, and then a whole new era appeared. More and more advanced biological worlds have better decorated the earth.

4. Write a short scientific article and introduce some scientific knowledge.

Memory has always been regarded as a unique function of organisms, especially higher organisms. However, materials scientists found in their research that some metals also have memory function.

In the 1960s, researchers in the US Naval Ordnance Laboratory made a NiTi alloy wire with 55% nickel and 45% titanium. They wound this nickel-titanium alloy wire into a spiral coil, heated it to 150℃, and then cooled it and straightened it. When the alloy wire was heated to 95℃ again, an incredible scene appeared-the wire automatically curled into the shape of the original spiral coil. The researchers cooled it and straightened it again, but when heated to the same temperature, it would return to its original shape. Repeat the experiment again and again.

Later, scientists discovered other alloys, such as Cu-Zn-Al alloy, Cu-Ni-Al alloy and Fe-Pt alloy. , also has the function of this shape memory. They call these alloys "shape memory alloys".

This alloy with shape memory function can be widely used in satellite antenna, aircraft hydraulic system, pipe riveting, medical equipment and many other fields. For example, antennas made of them are usually folded very small. When the spacecraft is in the sky, the antenna will expand into a hemisphere with a diameter of several meters under the irradiation of sunlight; Artificial bone tie rods made of them can rely on human body temperature to assemble and fix broken bones, which greatly speeds up the speed of fracture healing. Agree 0| Comment

5. Extract thirty scientific common sense about life.

1. Spread some toothpaste evenly on the collar and cuffs, brush lightly with a brush, and then rinse with clear water to remove stains.

As long as you put a bowl of vinegar in the new room, the smell of paint in the new room will soon disappear in two or three days. 3. The cuff or collar of the sweater will lose its elasticity. You can soak the cuff or collar in hot water for 20 minutes, and then dry it to restore its elasticity.

4. Soak the aluminum products with black spots in the mixed solution of vinegar and water, and take them out for cleaning after 10 minutes, and they will be as clean as new. 5. Soak the newly bought jeans in strong salt 12 hours, and then wash them with clear water, so that the color will not fade easily in the future.

6. When you buy a down jacket, you can put it on the table and pat it with your hands. The higher the fluffy degree, the better the cashmere quality and the more cashmere content. 7. After the surface of gold jewelry is worn, gently wipe it with deer skin (or other soft skin) dipped in a little toothpaste to make it as bright as new.

8. To remove the dirt in the oven, please sprinkle salt when the oven is still hot and wipe it with a wet sponge after cooling. 9. Indoor plants, such as chrysanthemum, ivy and chlorophytum, are natural air fresheners.

10. Wipe with 45 ml of white vinegar and 4 liters of cold water to make the window glass clean and transparent. 1 1. When cutting vegetables such as onions, peel them first and put them in the freezer for a few hours before cutting them to avoid tears.

12. When traveling, put fresh ginger slices under the nostrils at any time to make the spicy taste inhale into the nose, which can prevent carsickness. 13. A lot of dust often accumulates in the cracks of household appliances, so it is very convenient to remove it with a used brush.

14. burning dry tea leaves in the bathroom and smoking can remove the stench of dirty places. 15. Add a small amount of soapy water (or tea) to the ink and mix well. The handwriting written in this ink can keep the color trace unchanged.

16. If the CD is scratched accidentally, just paint it on the scratch with an oily pen, no matter what color it is. 17. The price tag is hard to tear off. You can heat it with a hair dryer before tearing it off, which will make it easy to tear it off without leaving any trace.

18. Fresh eggs are illuminated with lights, and the bear is very small. The egg is completely transparent and orange-red. There are no black spots and no red shadows in the egg. 19. After washing your face, gently rub your fingers with some fine salt on both sides of your nose, and then rinse with clear water to remove the blackheads.

20. As long as you put a smooth silk scarf on the pillow before going to bed, you can prevent the newly made hair from being deformed. 2 1. Add 6 egg whites to 1 kg flour, and the wrapped jiaozi will collect water quickly after taking out of the pot, which is not easy to stick.

22. Soaking the remaining tea leaves in water for a few days and pouring them on the roots of plants can promote the growth of plants. 23. Use dried tangerine peel when stewing meat, which is rich in flavor; Eating beef and mutton with angelica dahurica can remove fishy smell and increase freshness; The cinnamon of homemade sausage is delicious.

24. Soymilk can't be drunk with drugs. Drugs will destroy the nutrients of soy milk, such as tetracycline and other antibiotics. 25. When frying poached eggs, drop a few drops of hot water around the eggs. Fried eggs are especially delicious.

26. Take some fresh orange peels, put them in the refrigerator and open the refrigerator three days later. It smells good and has no peculiar smell. 27. Radish and mutton can be cooked together, or some mung beans can be put in the pot.

28. Drinking green tea in the morning can stimulate appetite, refresh your mind, and soaking in medlar in the afternoon can enhance your physique and help you sleep. 29. Wash the fish and soak it in rice washing water for two hours. The fish made in this way tastes fresh and delicious.

Don't drink tea immediately after eating meat. Tea contains a large number of target acidic proteins, which can cause fatty liver. 3 1. Any red or purple cotton fabric can be as bright as new if it is washed with vinegar and water.

32. Eating an apple on an empty stomach in the morning and evening is beneficial to the treatment of constipation in middle-aged and elderly people. 33. After the kitchen floor has accumulated oil stains, before mopping the floor, pour some vinegar on the mop to easily remove the oil stains.

34. Remember to drop fresh lemon juice before the barbecue. VitC in lemon not only increases flavor, but also has detoxification effect. Flowers inserted in bottles can be kept fresh by adding a few drops of white vinegar or bleach to clean water.

6. Short essay on urgent ~ ~ ~ scientific knowledge (100 words or less)

There are many kinds of scientific knowledge. What do you want? Such as biology, physics, chemistry and so on.

Provide some topics of scientific papers for reference. What are the types of scientific papers on weather modification? How to write a scientific paper? Why can clothes keep people warm? Electromagnetic runway color projection small magnetic needle student scientific papers model essay to be an innovative person. Don't waste rubbish. Why are shoes getting brighter and brighter? What can we do for bioenergy? Are twins really telepathic? Why do popsicles steam? How to write scientific papers according to the new theory of dark matter? Be an innovative person. Science and technology club and I can fly without opening the door, and we can see the door. Can outsiders add vinegar to the water when cleaning umbrellas and raising flowers? The invention of intelligent ground garbage collection device-the wonderful use of folding scale ash. Why didn't the Great Wall fall down for thousands of years? By studying the foraging habits of spiders, the vitality of mantis plants will also sleep. On the relationship between buoyancy and gravity when objects float, what harm does duck's magical saliva have to the experiment of oil smoke in ink kitchen?

7. Scientific and cultural knowledge essay

Improve scientific and cultural knowledge and self-cultivation.

1, with certain literary knowledge, can improve the ability to understand problems and express language, help to conduct business negotiations, sum up business experience and improve the level of economic management.

2. Have a certain knowledge of philosophy, history and psychology, be able to improve the ability to analyze and understand problems, be good at handling various contradictions in enterprise management, coordinate various relationships, master public psychology, and adopt different methods to meet different objects according to their characteristics and requirements.

3. Have certain economic and legal knowledge, be able to master economic laws, act according to law, and improve work ability.

4. Having a certain knowledge of aesthetics, music and painting can cultivate sentiment, purify the soul, make people elegant, energetic, active and enthusiastic, chic and confident.