Acquired inheritance is the abbreviation of "acquired trait inheritance", which refers to the phenomenon that an organism, influenced by external environmental conditions and subjective will, produces adaptive and directional trait changes and can be passed on to future generations. Acquired inheritance emphasizes that external environmental conditions and willingness to survive are the main reasons for biological variation and promote biological evolution.
Acquired inheritance is a very intuitive, easy to understand and accept genetic phenomenon, which comes from people's observation of some phenomena in the process of interaction between organisms and the environment, as well as the observation of heredity and variation in the process of reproduction, and the biological attributes inferred through comparison, analysis and synthesis.
Lamarck put forward the judgment of acquired inheritance, which comes from the observation of biological phenomena and the feeling and judgment gained from experience. In fact, Lamarck is not the only one who has this feeling, but many people also have it.
Darwin initially opposed Lamarckian thought, but later he realized the important role of environment in biology and admitted that accessibility can be inherited. For the existence of degenerated and atrophied organs such as cecum, Darwin thought it was the result of utilization and discarding. Some organs that are not commonly used are passed down from generation to generation, and finally they are not used at all. He gave many examples, such as some birds on Pacific islands. Because there are no birds of prey on them on the island, they don't have to fly around easily. As a result, their wings were useless and they lacked practice for a long time. Finally, their wings can't fly.
The reason why the theory of acquired heredity has caused various criticisms is that it is extremely difficult for people to try to prove it by experiment. The course of biological evolution usually greatly exceeds the life span of researchers. According to Laplace's theory, acquired inheritance is a long historical process, and it is unrealistic to verify it through several generations and experiments.
In terms of time, the small variation of species is imperceptible in a short time. In addition, it is difficult to judge which mutations are adaptive and which are not. It takes a long accumulation process to become a more obvious difference and be discovered.
Acquired inheritance is Lamarck's description of biological genetic phenomenon on the basis of careful observation, and it is a kind of speculation and judgment. One of the striking features of modern biology is its experimental nature. However, in Lamarck's time and after that, biology was largely a descriptive science.
Before discussing the problem of acquired inheritance, let's look at some biological phenomena.
Camels are called "ships in the desert". Camels have evolved the equipment and functions needed to survive in the desert.
Camel's feet are flat, and there are thick and soft meat pads under their feet. Such feet allow camels to walk freely in the sand and not easily fall into the sand.
Camels have hair in their ears, which can prevent sand from entering; Camels have double eyelids and thick long eyelashes, which can prevent sand from entering their eyes.
Camels have strange noses, and their nostrils can be opened and closed. Whenever a sand cyclone blows in the desert, its nostrils will be closed and can be easily opened and closed like a door.
There is a hump on the camel's back, which stores fat. You can eat nothing for four or five days in a row and only rely on the fat in the hump.
The stomach has three chambers. The first stomach chamber has 20-30 puddles, which can store water. Red blood cells can greatly expand, absorb water and store water, so they can resist hunger and thirst, and they can not eat or drink for many days. Once they meet the water source, they can drink plenty of water for storage.
Besides camels, there are other desert animals, including snakes, mice, small insects in the desert, and the bigger one is the desert fox.
Due to climatic reasons, animals in the desert have some similar characteristics: they have the ability to retain water, resist high temperature and adapt to desert life. For example, we can use the water produced by the decomposition of organic matter to reduce skin breathing, form high-tension urine, behave at night, and evaporate heat by sweating and panting, which is similar to the body color of sand and flat and wide feet. In addition, the tolerance to hunger is much greater than that of related species, and most of them have the ability to move, which is related to obtaining low-density and scattered prey, showing physiological characteristics of adapting to a specific environment.
Let's go to the cold North Pole again and learn how the animals in the North Pole adapt to the ice and snow environment.
The most typical animal in the Arctic is the polar bear. Polar bears are covered with thick white hair (white in appearance, but actually transparent), but their skin is black. We can see the original appearance of their skin from the black skin around their noses, paw pads, lips and eyes. And dark skin helps to absorb heat.
Polar bears have special hair, too. Their hair is hollow in the middle. This structure can reflect sunlight to the dark skin under the hair and help absorb more heat.
The thick fat layer under polar bear skin further isolates the cold from the body. Polar bears are so effective in keeping warm that they sometimes have to lie on the ice to cool down. Although polar bear's hair doesn't change into dark summer clothes like other Arctic animals in summer, it may turn yellow slightly due to oxidation.
Polar bears have wide front paws, like swimming paddles, which control the direction of progress. The four paw pads are covered with thick hair, which not only helps to keep warm, but also facilitates them to walk on the ice.
Polar bears have the same vision and hearing as humans, but their sense of smell is extremely sensitive, seven times that of dogs.
In addition to polar bears, other animals living in the Arctic, such as arctic foxes and rabbits, have also evolved characteristics suitable for cold environments. Arctic foxes also have dense hair on the soles of their feet, which is suitable for walking on ice and snow. Arctic fox fur is white, long, soft and thick, and can resist cold. From spring to summer, it gradually turns blue-gray, which is called "blue fox".
Arctic rabbits have a feature that they can change the color of their fur with the seasons. It is taupe in spring, summer and autumn, and becomes innocent in winter, which is convenient for camouflage and can play an optical reflection role, and is not easy to be discovered by natural enemies. Fluffy fluff captures some air around its body, just like a hollow wall, forming an insulating layer, which effectively prevents the loss of heat, which is very important for spending the winter in the Arctic.
We can also look at some examples here. If we put some domestic animals in the wild, such as dogs, pigs, cats, rabbits and so on. After several generations, these animals will gradually restore the characteristics of the wild ecology, the previously artificially imposed characteristics will gradually disappear, and the memories of their ancestors in the wild environment will be awakened.
Many people know that the invasion of exotic species in Australia is a regrettable thing. Some domestic animals from other continents were brought to Australia, such as rabbits, dogs and pigs. These animals were released into the wild, and they quickly adapted to the local environment and changed from domestic animals to wild animals.
There are also negative examples. For example, chickens under domestic conditions, because they are kept in captivity for a long time, their wings do not need Yu Feixiang, so the degradation becomes smaller; At the same time, the decrease of activity leads to the decrease of breathing ability and airbag. This degenerated behavior and structure has been stably inherited in domestic chickens.
Let's talk about animals and people.
Tell me why there are people with different skin colors.
The color of skin is mainly determined by the content of melanin in skin. Melanin is a kind of black or brown particle, whose main function is to block the damage of ultraviolet rays in sunlight to human subcutaneous cells. When the sun is strong, the content of melanin increases, so we will be tanned in summer.
The color of human skin is the result of adapting to different nature. We find that human skin color changes gradually with the latitude of the earth. Africans living in the equatorial region have black skin, because their skin is often exposed to strong sunlight, and melanin is produced in large quantities. There is less light in cold areas, so the skin is white. Yellow people generally live in temperate regions, with moderate sunshine intensity and melanin in between, so their skin color is also in between. Human ancestors moved to different areas, and in order to adapt to the external environment, the difference of skin color gradually appeared.
In fact, the differences between different races are not only manifested in skin color, but also in many other aspects, such as nose, eyes, hair and so on. These differences are caused by the long-term impact of the environment.
People's skin color, physique, hair color and facial features are all related to local climate, temperature, light and other environmental conditions. People in different areas have different living habits, eating habits and even cultural traditions, which may have an impact on health.
? Different regions, different climates and different living habits are the reasons for the differences. Environment can change people. If Europeans live in Asia for generations, as long as there is enough time, even if they don't marry Asians, the skin color of future generations will gradually move closer to the locals.
? Another example around us is the change of skin color of China people. Some people say that China people's skin is constantly turning white, which is related to the increase of indoor activities. In the past, people in China had been engaged in agricultural labor for a long time, and their skin was blackened by the wind and sun. Most modern people work or work indoors, and with the shortening of exposure to sunlight, their skin will become whiter and whiter. This phenomenon is obvious. With the acceleration of urbanization, fewer and fewer people are engaged in outdoor work, and the skin of the next generation of China people tends to be whiter and whiter. A change in skin color is a genetic change.
Therefore, people's different skin colors are closely related to the lighting environment.
? With the development of society and the improvement of people's living conditions, people are changing from appearance to intelligence. If you look at the photos of junior high school students in the 20th century, according to the present aesthetic standards, there are only two words-ugly, not only black but also rough, and the outline of face and body does not conform to modern aesthetics. Some people who were once called beauties are now passers-by. Intellectually, many parents think that children nowadays are smarter than in the past. With the development of society, people are changing both internally and externally. Sometimes we can't help but feel that the speed of biological evolution is much faster than we thought.
In the past, in an isolated area, people's cultural level and intelligence were relatively low. If people in such a region can accept foreign culture and education and change their past self-isolation, people's cultural and intellectual level will gradually come up. People can improve their genes through their own efforts. The popularization of education is the fundamental driving force for a country's development.
Social background and national education can determine a person's character and connotation, and people will achieve biological success through their own efforts and social help.
In the same environment, although there are differences between people, as a whole population, there will be no sharp differentiation between people, because the environment works on people at the genetic level.
Too rich environment will also affect people's development. Some places have superior natural conditions, rich natural mineral resources and good national welfare. People can live well without too much effort. Such an environment can easily lead to people's laziness in thought and behavior, people's lack of progress, and people's fall.
People may wonder why Africa's development is slower than other continents. One of the important reasons is the natural environment. Africa is very hot all year round, plants grow all year round, and food can be found on trees and on the ground, so you can pick it while eating. For a long time, the living habits of Africans are not much different from those of apes, which leads to Africans' loose personality and lack of enterprising spirit, and their races can not be better improved and improved. Europe is different from Asia. There are four seasons in a year. People must find ways to spend the season of food shortage, which leads to grazing and farming. The harsh environment forces people to keep forging ahead, develop various survival skills, and gradually develop agricultural production and related social activities, which naturally affects heredity.
There are many kinds of creatures in nature, all of which are developing in the direction of adaptive evolution, and nature has shown amazing creativity. There are too many examples of biological adaptability. This phenomenon occurs in all species, from which we perceive that there is some order behind the evolution of life. For organisms living in different environments, they have characteristics corresponding to specific environments, and some biological functions have corresponding biological structures, rather than developing aimlessly. Biological characteristics are inextricably linked with the environment. For different survival needs, organisms have evolved different solutions. After a long period of evolution, organisms show infinitely complex and precise structures.
Can we imagine that all these phenomena are the ability of organisms to extract information from the environment? The change of biological characters is due to the reaction between biomolecules and the environment, not the result of random variation. Biological evolution is directional, and there is a corresponding change mechanism between biomolecules and the environment.
Let's look at some more examples.
Almost everyone knows that bacteria will develop drug resistance. Why is there drug resistance?
Bacterial drug resistance refers to the directional evolution of bacteria in the process of contact with drugs. Bacteria make drug-resistant genes through their own adaptive response, and then all bacteria share this achievement through transmission, so there are more and more drug-resistant bacteria. This shows that bacterial biomolecules have the ability to adapt to the environment. When the environment is not conducive to their own survival, they will resist the invasion of the outside world and maintain their own existence through the adjustment of their genetic structure. This ability can be inherited.
Drug resistance of bacteria is very common. Why is bacterial drug resistance a common phenomenon, and almost all bacteria will appear? Who can guarantee that the mutation of every bacteria is beneficial to survival? Therefore, it is far-fetched to explain the formation of bacterial drug resistance by accidental mutation.
The argument put forward by those who deny acquired inheritance is that, for example, a person's exercise produces strong muscles, and his muscles will not be passed on to the next generation; A person has rich life experiences or experiences, which will not be directly passed on to the next generation. People's muscles are not inherited, but the offspring of strong individuals usually have a stronger physical foundation than others and are more likely to develop into strong bodies. Although Schwarzenegger's muscles cannot be directly transmitted to his son, his son (grandson) has a better physical foundation than the descendants of ordinary people; The descendants of an experienced person usually have better intellectual talent and stronger understanding and judgment. Genetic genes show a potential ability to be expressed, which may not be expressed in the next generation, but may have an impact on future inheritance.
Herbivores and carnivores on the African grassland have strong running ability in the long-term survival competition. This running ability is constantly improved in the process of chasing each other from generation to generation, and the acquired behavior is embedded in biological genes bit by bit, which is manifested in the continuous strengthening of this ability in the process of adaptation.
There are many similar examples, such as so-called artistic cells, language ability, performance ability, painting skills, musical talent and so on. Talent comes from some activities that predecessors have engaged in. Talent may not be shown in every descendant, but it has a high probability. These innate abilities don't happen to someone by accident, but come from the genetic imprint left by heredity or predecessors' activities, which is called acquired characteristics.
Because the material basis of "possessiveness" is formed by the movement of organisms, with the continuous movement, its material will change from quantity to quality. The longer the exercise time, the deeper the qualitative change, and the deeper and more stable the "learnability". If what we mean by possessiveness is the change of a generation's character relative to its parents, then the change of this generation is extremely weak relative to the cumulative change of its ancestors. This "micro" means that its quantity is small and not easy to detect; This "weak" means easy to change. It can be changed through personal constant new exercise. When it is passed on to future generations, it can also be changed by new movements carried out by future generations in the new environment. At the same time, this generation of acquisitions are also different in scale and quality. People occasionally blister on their working hands, which has no effect on their health. After a few days' rest, the blisters will disappear by themselves, and it is difficult to affect future generations. If you engage in heavy physical labor for a long time, it will make the whole body change qualitatively, thus affecting future generations. Some people use examples such as blisters on hands and sunburn to show that acquired inheritance is not inheritance. Is tanning hereditary or not? There are also qualitative and quantitative differences in skin tanning. At the same time, there are many factors that affect skin color, including the influence of both parents and the influence of the acquired environment. The influence of the first generation is extremely weak. If men and women live in strong sunlight for generations, they will see significant changes through gene accumulation. Today, people of different colors: black, white, yellow, brown, etc. Their different skin colors just correspond to the different sunlight intensities received by their ancestors living in different latitudes, indicating that it is related to sunlight stimulation and is the result of gene accumulation.