How did "men and women" come into being?

How did "men and women" come into being? Over the years, there have been two major factions in the decision on gender. One school advocates "environment determines sex" and the other advocates "heredity determines sex". The former thinks that the environment, dietary characteristics and mental state of pregnant women can affect the formation of fetal sex. Only the theory of genetic sex determination is introduced here.

(a) the theory of chromosome sex determination

This theory holds that sex chromosomes determine the sex of men and women. In human normal karyotype, XY sex chromosome determines the gender development of normal men; And XX determines the gender development of normal women.

During the formation of parental germ cells, after meiosis, the two sex chromosomes are separated from each other, and men produce two types of * * *-* * band X chromosomes and * * * band Y chromosomes. Women only produce one kind of egg cell with X chromosome. During fertilization, if * * * containing X is combined with the egg, it will produce a fertilized egg containing XX and develop into a female; If the Y-containing * * * is combined with the egg, a fertilized egg containing XY will be produced and developed into a male. This shows that when the fertilized egg is formed, the gender of men and women has been determined. Because men can produce an equal number of X *** and Y ***, and the probability of combining with eggs is equal, so the probability of giving birth to boys and girls is equal every time. The sex ratio of the whole population is roughly 1: 1.

(b) the theory of genetic sex determination

In a few human cases, those with karyotypes 46 and XY are completely normal females, and those with karyotypes 46 and XX are normal males. In this way, the theory of chromosome sex determination cannot explain this special phenomenon. So someone put forward the theory that genes determine sex.

In the late 1970s, Wachtel and others proposed that there was an H-Y antigen gene on the short arm of human Y chromosome, and its product was a hydrophobic protein with molecular weight of 18000, which was called H-Y antigen. In the process of embryonic development, H-Y antigen has a directional effect on gonads, which can differentiate the genital ridge with sexual differentiation potential into testis, so H-Y antigen gene is also called testis determinant. In the presence of H-Y antigen, testis develops. Without H-Y antigen, the genital ridge will naturally develop into an ovary, and then further develop into female internal and external genitalia. In other words, the theory holds that sex depends on the existence of H-Y antigen gene-TDF. A candidate gene ZFY encoding TDF zinc finger protein has been cloned abroad, and the female gene is ZFX. The sex-determining gene locus is Yp 1 1.32 for male and Xp2 1.3 for female. Because this gene plays a decisive role in sexual differentiation, it is called "gene-determined sex theory" karyotype 46. XY is a woman because there is no testicular determinant-TDF gene on her Y chromosome.

At present, the theory of chromosome sex determination has been gradually replaced by the theory of gene sex determination.

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Generation of gender

Generally speaking, of course, it is the result of evolution and natural selection.

Why does natural selection produce such a result? Of course, it is conducive to the survival of living things. After the birth of biological sex, one biological individual can complete the task of reproduction and become two male and female individuals to cooperate to complete the task. It should be said that it is a kind of trouble, inconvenience and limitation. The number of offspring is also reduced to half of the original possibility, that is, the ability to spread offspring is reduced to half of the original. If you consider the troubles, inconveniences and limitations. Then after the birth of a gender, the reproductive ability of a single individual with a gender will be reduced even more. The reproductive capacity will probably be 30% or even lower, such as 20%.

The reproductive capacity is greatly reduced, but these sexual creatures are everywhere and should be the winners of evolution. Why is this? The answer lies in the survival adaptability of future generations. The offspring produced by sex are genetically different or slightly different. This little difference is the fundamental reason that determines the strong viability of sexual creatures. Because of this difference, the ability of different offspring of the same creature to adapt to the environment is different, that is, these different offspring adapt to different optimal environments. Although their optimal environments are very different, they are of great significance.

The offspring of asexual organisms have no genetic differences, but of course they can only be exactly the same and adapt to the same optimal environment. This is also very important, which is a big shortcoming of asexual organisms. The offspring of many asexual individuals can only compete with each other in the best environment. If the environment changes slightly, it will not adapt. But the offspring of sexual creatures have slightly different genes and the best adaptation environment. Therefore, the offspring with slightly different genes are in the best development prospect in their own best environment, which reduces the degree of competition with their own species, while the offspring of those creatures without gender can't do this. This is also one of the benefits of sexual creatures.

The more important benefit is that. The living environment of living things is changing, so living things must keep up with this change. There are differences in adaptation to environmental changes between sexual and non-sexual biological individuals. Because the environment is generally long-term, the adaptation environment is different, and the environment has changed a little. Among the descendants of many sexual creatures, there is always an individual who is most adapted to this environment, and this individual who is most adapted to this environment is of course the fastest growing. Soon, there are more and more such experiences and they are in an advantage. Other individuals do not adapt to the new environment and gradually decrease. And those creatures without sex, everyone's genes are the same, they have to adapt, and they have all adapted. Not adapting is not adapting. The environment has changed a little. Generally speaking, they are not suitable and will be eliminated. But it is inappropriate for us to think so completely, because organisms can mutate. The probability of genetic variation exists. Some organisms have higher probability of genetic variation, while others have lower probability of genetic variation.

The genes of the offspring of those creatures without sex are not exactly the same because of variation. If the environment changes slightly, the offspring of those creatures without sex may be the most adaptable. But few, if any. Because the probability of genetic variation is extremely small. It can be seen that it is too difficult to adapt offspring to the new environment through genetic variation, which is a last-minute cramming. The offspring of those sexual creatures are really prepared, have no genetic variation, and can often adapt to the new environment.

Sexual creatures have genetic variation, but it has been accumulating, those excellent genes, or seemingly worthless mutant genes, or even temporarily harmful genes. Really prepared. Asexual organisms are constantly mutating, but they cannot accumulate, because unfavorable mutation will lead to the extinction of individuals. However, sexual organisms can store many harmful genes and do not necessarily show the traits controlled by this gene. But these harmful genes may be beneficial after environmental changes. Therefore, sexual organisms are more adaptable to environmental changes than asexual organisms and have great advantages. Although the sexual generation greatly reduced their reproductive ability, the sexual generation maintained their genetic diversity and greatly enhanced their ability to adapt to different environments. This drop of one liter, on the whole, sexual creatures still take advantage. Otherwise, there wouldn't be so many sexual creatures in the biological world. The generation of gender is also the inevitable result of biological development.

Asexual organisms also exist in large numbers. Why? The reason is probability. The offspring of asexual organisms are mutated. Asexual organisms have great advantages in reproduction. If asexual organisms have strong reproductive ability, they can reproduce a large number of offspring in a short time. Many descendants of these asexuals are mutants. Maybe one of these variants will adapt to the new environment, and one will be enough. There will be many descendants soon. These are the reasons why asexuals still exist today.

Asexual organisms and sexual organisms coexist, each with its own advantages. One is strong reproductive ability, and the other is that the bred offspring have strong adaptability to different environments.

Those creatures with strong reproductive ability are generally smaller creatures. The reproductive ability of larger organisms is relatively weak, so larger organisms are generally sexual organisms.

There are also some creatures that can reproduce sexually and asexually. Mainly some lower animals or some higher plants. This is also an interesting evolution.

How does the love between men and women come into being?

How do the feelings of boys and girls come about? Feelings, if at arm's length, or hidden or present, may be some kind of need or dependence of people. For example, when you are misunderstood by others and empty-handed, someone stubbornly holds your hand, giving you warmth and touching you. Maybe the feeling that you are moved is a feeling at this time. Personal opinion, I hope it helps.

How do beautiful women come into being? How do you produce beautiful women, how do you produce thiamine ... hehe.

Seek adoption

How do leftover women come into being? Because handsome guys like handsome guys ~

How do men and women come into being? Generally speaking, it is of course the result of evolution and natural selection.

Why does natural selection produce such a result? Of course, it is conducive to the survival of living things. After the birth of biological sex, one biological individual can complete the task of reproduction and become two male and female individuals to cooperate to complete the task. It should be said that it is a kind of trouble, inconvenience and limitation. The number of offspring is also reduced to half of the original possibility, that is, the ability to spread offspring is reduced to half of the original. If you consider the troubles, inconveniences and limitations. Then after the birth of a gender, the reproductive ability of a single individual with a gender will be reduced even more. The reproductive capacity will probably be 30% or even lower, such as 20%.

The reproductive capacity is greatly reduced, but these sexual creatures are everywhere and should be the winners of evolution. Why is this? The answer lies in the survival adaptability of future generations. The offspring produced by sex are genetically different or slightly different. This little difference is the fundamental reason that determines the strong viability of sexual creatures. Because of this difference, the ability of different offspring of the same creature to adapt to the environment is different, that is, these different offspring adapt to different optimal environments. Although their optimal environments are very different, they are of great significance.

The offspring of asexual organisms have no genetic differences, but of course they can only be exactly the same and adapt to the same optimal environment. This is also very important, which is a big shortcoming of asexual organisms. The offspring of many asexual individuals can only compete with each other in the best environment. If the environment changes slightly, it will not adapt. But the offspring of sexual creatures have slightly different genes and the best adaptation environment. Therefore, the offspring with slightly different genes are in the best development prospect in their own best environment, which reduces the degree of competition with their own species, while the offspring of those creatures without gender can't do this. This is also one of the benefits of sexual creatures.

The more important benefit is that. The living environment of living things is changing, so living things must keep up with this change. There are differences in adaptation to environmental changes between sexual and non-sexual biological individuals. Because the environment is generally long-term, the adaptation environment is different, and the environment has changed a little. Among the descendants of many sexual creatures, there is always an individual who is most adapted to this environment, and this individual who is most adapted to this environment is of course the fastest growing. Soon, there are more and more such experiences and they are in an advantage. Other individuals do not adapt to the new environment and gradually decrease. And those creatures without sex, everyone's genes are the same, they have to adapt, and they have all adapted. Not adapting is not adapting. The environment has changed a little. Generally speaking, they are not suitable and will be eliminated. But it is inappropriate for us to think so completely, because organisms can mutate. The probability of genetic variation exists. Some organisms have higher probability of genetic variation, while others have lower probability of genetic variation.

The genes of the offspring of those creatures without sex are not exactly the same because of variation. If the environment changes slightly, the offspring of those creatures without sex may be the most adaptable. But few, if any. Because the probability of genetic variation is extremely small. It can be seen that it is too difficult to adapt offspring to the new environment through genetic variation, which is a last-minute cramming. The offspring of those sexual creatures are really prepared, have no genetic variation, and can often adapt to the new environment.

Sexual creatures have genetic variation, but it has been accumulating, those excellent genes, or seemingly worthless mutant genes, or even temporarily harmful genes. Really prepared. Asexual organisms are constantly mutating, but they cannot accumulate, because unfavorable mutation will lead to the extinction of individuals. However, sexual organisms can store many harmful genes and do not necessarily show the traits controlled by this gene. But these harmful genes may be beneficial after environmental changes. Therefore, sexual organisms are more adaptable to environmental changes than asexual organisms and have great advantages. Although the sexual generation greatly reduced their reproductive ability, the sexual generation maintained their genetic diversity and greatly enhanced their ability to adapt to different environments. This drop of one liter, on the whole, sexual creatures still take advantage. Otherwise, there wouldn't be so many sexual creatures in the biological world. The generation of gender is also the inevitable result of biological development.

Asexual organisms also exist in large numbers. Why? The reason is probability. The offspring of asexual organisms are mutated. Asexual organisms have great advantages in reproduction. If asexual organisms have strong reproductive ability, they can reproduce a large number of offspring in a short time. Many descendants of these asexuals are mutants. Maybe one of these variants will adapt to the new environment, and one will be enough. There will be many descendants soon. These are the reasons why asexuals still exist today.

Asexual organisms and sexual organisms coexist, each with its own advantages. One is strong reproductive ability, and the other is that the bred offspring have strong adaptability to different environments.

Those creatures with strong reproductive ability are generally smaller creatures. The reproductive ability of larger organisms is relatively weak, so larger organisms are generally sexual organisms.

There are also some creatures that can reproduce sexually and asexually. Mainly some lower animals or some higher plants. This is also an interesting evolution.

How did FOTRIC come into being? This involves trade secrets, mainly including design, processing, assembly, testing, calibration and other procedures. If you say something, don't say it. I strongly recommend that you visit the site.

How did fire come into being? Fire is the light and heat produced by the burning of matter, and it is a kind of energy. Combustible, ignition point and oxidant must coexist to catch fire. All three are indispensable. Fire is a plasma state between gas, solid and liquid. Fire is composed of substances in plasma state (pla *** a), and pla *** a is the fourth state of substances defined by British physicist Sir william crookes in 1879 (the other three are solid, liquid and gaseous). When electrons leave the nucleus, this process is called ionization. At this time, the substance becomes a uniform "paste" composed of positively charged nuclei and negatively charged electrons, which is called ionic slurry. These plasmas have equal total positive and negative charges, so they are also called plasmas. The fire we usually see is the photon emitted by ionized electrons when they return to the ground state from the excited state. Photons with different energies have different colors. Does fire have gravity? The answer is yes, because the shape of the fire in the weightless space capsule is spherical, and its shape is influenced by gravity. From the macro definition of matter, fire is matter, because from the macro definition of philosophy, the state of matter is also matter, and matter and state are not contradictory. Fire is the basis of diet and cooking. It should be said that with fire, there is a food culture. Before the birth of fire, the ancestors could only live a primitive and animal-like life. The so-called "eating the food of vegetation, the meat of birds and beasts, drinking their blood, like their hair." As Han Feizi said, "People eat fruits and clams, and their stomachs are injured by foul smell, which leads to many diseases." After the birth of fire, "guns are familiar to people, making people have no abdominal diseases and different from animals." The inventor of fire, China, has always been said to be a man who drilled a fire to make a fire. Archaeologists preliminarily speculated from the stone tools used by Beijingers in Zhoukoudian that China people began to use fire consciously, about 500,000 years ago. There are three emperors and five emperors in the history of China, and there are at least four versions of Huang San. One version is Fuxi, Shennong, Huangdi (the world book, the imperial century); There is a saying that Fuxi, Nv unfortunately and Shennong (Ji, customs pass); One view is Fu Xifei, Shennong and Zhu Rong (White Tiger Boy); There is also a saying that Fuxi, Shennong and Suirenshi (Baihutong). Suiren must be after Fuxi Shennong. Because according to China folklore, since Fuxi, the king of the imperial court has owned the world; Fuxi was followed by Bai Huangshi, Zhong, Shi, Li, Zunjie, Zhu Rong, Chaos, Shi, You Chaoshi, Ge, Kang Yinshi, Zhu Shixiang, Wu Huaishi and Sui Renshi, all of which attacked Xi Shi (Zhu Xiang family). Corpse: "Look up at the stars, look down at five trees and think it's fire." According to the five elements of yin and yang, fire is born in wood, so people use wood to make a fire. "The History of Taoism" says that embarrassing people is to watch the dry elephant, watch the heart and get out of the fire, and make embarrassment. According to the ancients, "Chen Xin" is called "Xinsu", that is, "Big Mars". The so-called "five wood" refers to five kinds of wood that are considered suitable for fire at the right time. That is, "Yu; Liu Qing, so bring it in spring; Jujube: apricot red, so eat it in summer; Sang: Huang Zhe, so I took it at the end of summer; Tussah: (Mukui) white, so take autumn; Sophora japonica; Suntanned, so bring it in winter. " After a man drills a fire, his wooden drilling tool is called fire. Later generations invented using metal to take fire from the sun, so there are two kinds of "wood fire" and "yang fire". "Huainanzi" notes: "Yang Sui sees the sun and burns into a fire. Yang Xiang, Jin Ye. The sun is three or four feet high, and if you cling to the sun, you will be angry for a moment. " "Notes on Ancient and Modern Times": "The pith of yang is copper, which is shaped like a mirror. When you look at things, the scenery falls and you light a fire at the sun. " Before the Han Dynasty, it was called "open fire" to make a fire with incense, and "national fire" to make a fire with wood. According to the "Great Wish" and "Great Reconnaissance" in Zhou Li, the yang marrow is taken from the sun and close to the sky, so it is used for divination and sacrifice. Wood is taken from five trees and is close to people, so it is used for cooking. After the Han dynasty, when a metal hits a stone, it can also be rubbed into fire, so a simple piece of iron can be turned into a yang sui. When people go out, they usually wear Yang Xiang and Mu Xiang on the left side of their waist to make a fire at any time. In addition, there are tinder made of wormwood and salt water. When the spark falls on the tinder and burns due to friction, the fire is ignited by "lighting a candle". The so-called "hair candle" is a small piece made of peeled hemp stalks, which is five or six inches long. At first, it flows with sulfur and burns when it meets fire. Where there is fire, there is a stove. The person who made the stove said that it was Emperor Yan, and Huai Nanzi: "Emperor Yan died with fire as the stove." Note: "Yan Di Shennong ruled the world with fire and died in the kitchen god." One is the Yellow Emperor: "Continued Beginning": "The Yellow Emperor sets the stove." Therefore, "Everything must be the original" said: "The Yellow Emperor cooked and died as a kitchen god." And Vulcan, generally speaking, is Zhu Rong. Huainanzi? Note: "Zhu Rong Ng Wui, for the fire of Gao Xin, died as Vulcan, put his hand on the stove." Historical records? Chu family: "Li Dong lived in the fire for Di Ku Gaoxin and made great contributions. He can blend in with the world, and Di Ku called him' Zhu Rong'. " "The Book of Rites and the Moon Order": "The moon exists, its emperor, its god Zhu Rong and its sacrificial furnace are sacrificed to the teacher." The original shape of the stove was to dig holes in the ground. Today, the furnace excavated from Xi 'an Banpo site is a kind of double furnace, that is, two fire pits are dug on the surface. These two pits are separated on the ground, but they are connected underground. A pit is where firewood enters, a pit is where people leave, and the hole connected with the two pits is the stove door. Banpo in Xi 'an has a history of six or seven thousand years, and its inventor should be Emperor Yan rather than Yellow Emperor. It is estimated that the Yellow Emperor was in power about 4600 years ago. Emperor Yan passed down seventy generations before the Yellow Emperor, about six or seven thousand years ago. By the Warring States period, the production of stoves had been perfect. "Zeng Lianzi" notes: "There are five protrusions (protrusions: chimneys) in one furnace, and there are many people who distribute cigarettes, and it is cooked for ten times." Cooking with fire, the ancients immediately noticed the importance of heat for cooking. In ancient Chinese, the first talk about the importance of cooking is "Lu Chunqiu?" This flavor article. " Among them, Yi Yin told Shang Tang: "Water is the beginning of all tastes. Five flavors and three ingredients, nine boiling and nine changes, fire is the discipline. If you are sick, you will be slow. If you use it, you will win. Reconciliation must be bittersweet. How many times, its gas is extremely small, and there are changes, subtle and micro-fiber, plausible, plausible. If you shoot the slightest, Yin and Yang will transform, and the number of four seasons will be counted. It is harmless for a long time, ripe but not rotten, sweet but not tasted, sour but not cold, undiminished in work, pungent but not strong, light but not thin, fat but not [month]. "The general idea of this passage translated into vernacular is that water is the first of all tastes. Cooking is based on sweet, sour, bitter, spicy and salty flavors and Shui Mu fire. There will be nine changes when the pot is boiled for nine times, and it is up to the fire to explore and adjust. Sometimes with strong fire, sometimes with slow fire, the key to removing fishy smell and shame is to master the heat. Only by mastering the law of using fire can the odor be turned into fragrance. Seasoning must use five flavors of sweet, sour, bitter, spicy and salty, but the order of seasoning and the amount of materials used are very subtle. The change of Ding is subtle, subtle and indescribable, even if it is known, it is hard to say clearly. Just like putting an arrow on a horse, you should practice your cooking skillfully. Such as the natural combination of yin and yang, such as the natural transformation of the four seasons, cooking can be cooked for a long time, cooked but not rotten, sweet but not strong, sour but not astringent, spicy but not * * *, light but not tasteless, fat but not greasy.

How magnetism is produced is indeed a physical problem, and there is no clear scientific answer at present. Even if there is, it is also a scientific hypothesis.

How did the fart come from? Fart is the gas produced by the fermentation of food in the intestine by bacteria. In the large intestine, especially from the large intestine to the rectum, there are not less than 100 species of bacteria, and the number is about 100 trillion. They participate in the decomposition of food and are beneficial to the absorption of intestinal wall. In the process of decomposition, some harmful substances and gases will be produced, and these gases will become fart after concentration. An adult has about 7 ~ 10 liter of gas entering the intestine every day, most of which is absorbed by the blood vessels in the intestinal wall, and about 0.5 liter of gas is discharged from the intestine. This is the fart that people fart every day under normal circumstances, including the fart that has been restrained on some occasions. The fart that can't be released will be absorbed by the intestinal wall, enter the blood, and then be excreted through urine.

The main component of fart is nitrogen, accounting for about 23% ~ 80% of fart; Followed by carbon dioxide, accounting for about 20%; The third is hydrogen, methane and oxygen. The smell of fart comes from ammonia, hydrogen sulfide, indole, indigo matrix, odorous substances, volatile amines and volatile fatty acids produced by spoilage bacteria such as Escherichia coli when decomposing protein. Although the total content is less than 10%, it is enough to annoy listeners.

Fart is a dangerous gas, sometimes it contains as much as 47% hydrogen. Therefore, scientists warn that in this case, fireworks are strictly prohibited, and a little spark may cause an explosion. This is by no means sensational. There is a report abroad that during an intestinal operation, an electric knife was short-circuited to produce an electric spark, which caused the fart overflowing in the intestine to explode and blew up a section of the intestine. Fortunately, the hydrogen in the fart is not always kept at the critical value of detonation, and the fart entering the air will be diluted quickly. Even so, in some specific places, fart can't be taken lightly. For example, on the space shuttle, astronauts farting may cause sparks, and the consequences are unimaginable. To this end, in order to eliminate hidden dangers, NASA has also set up a special project and allocated funds to conduct a comprehensive, in-depth and systematic study on farting: what kind of food can make astronauts fart less during flight and prevent problems before they happen.

Fart also has certain application value in clinical diagnosis. If someone has abdominal pain and tears, it is suspected that they have an emergency. Who knows that after farting for a while, the abdominal pain suddenly eased, which is the fart at work. If the number of people does not fart, defecate and have abdominal pain, it is often a precursor to intestinal obstruction. If the fart rings repeatedly and smells bad, it may be related to indigestion or eating too much meat. If the fart sounds like thunder, but it doesn't smell too bad, it is mostly because of overeating food with too much starch (such as potatoes), which is caused by fermentation in the intestine. Therefore, it is helpful to ask the patient about the fart and understand the digestive function.

In addition, after abdominal surgery, surgeons are particularly concerned about whether the patient farts (medically called "exhaust"). If you fart repeatedly, it means that gastrointestinal peristalsis has returned to normal, which is a signal that patients can eat. On the other hand, if you still don't fart 3 ~ 4 days after operation, you should take corresponding measures to draw the fart out as much as possible. For people who have obvious flatulence in the abdomen and don't fart, intubation is sometimes used to give fart access. It can be seen that fart is very valuable in some cases.