How did dinosaurs die out?

Climate change says that 65 million years ago, the earth's climate changed suddenly and the temperature plummeted, which led to the decline of oxygen content in the atmosphere and dinosaurs could not survive. Some people think that dinosaurs were cold-blooded, without hair and warm organs, unable to adapt to the decline of the earth's temperature, and all of them froze to death. According to the theory of species struggle, the first small mammals appeared at the end of the dinosaur era. These animals are rodent carnivores and may feed on dinosaur eggs. Due to the lack of natural enemies, more and more small animals finally ate dinosaur eggs. The theory of continental drift geology proves that there was only one continent, Pangea, when dinosaurs lived. Due to the change of the crust, the Jurassic continent split and drifted, which eventually led to the change of environment and climate and the extinction of dinosaurs. Modern biology has proved that the death of some creatures is related to magnetic fields. When the earth's magnetic field changes, creatures sensitive to the magnetic field may lead to extinction. It can be inferred that the extinction of dinosaurs may be related to the change of the earth's magnetic field. Angiosperm poisoning says that at the end of the dinosaur era, gymnosperms on the earth gradually became extinct, replaced by a large number of angiosperms, which contained toxins that gymnosperms did not have. Giant dinosaurs ate a lot, and the intake of angiosperms led to excessive accumulation of toxins in the body and finally poisoning. Carnivores are poisoned after eating poisonous meat. Acid Rain It is said that there may have been strong acid rain at the end of Cretaceous, which dissolved trace elements including strontium in the soil. Dinosaurs ingested strontium directly or indirectly through drinking water and food, which led to acute or chronic poisoning and eventually died in batches. Meteorite impact said that there was a chicxulub crater in Mexico's Yucatan Peninsula. This kind of rock is called the K-T boundary by geologists, which means the marker line of the Cretaceous-Tertiary boundary. The lower rocks are rich in dinosaur fossils, but above the K-T boundary, dinosaurs disappeared. The rocks at the K-T boundary contain iridium, which is a rare metal with an average content of only one billionth in the earth. However, the iridium content in this rock layer is 200 times higher than the normal content. Where else can I find so much iridium? In space. The content of iridium in space is 1000 times higher than that of the earth. People also found evidence of shocked quartz in this layer of white rock, and only asteroids will leave such traces. High concentrations of iridium and shocked quartz occur in tertiary boundary rocks in many parts of the earth. This global trace can only come from the most violent impact. The impact site is now Yucatan Peninsula in Mexico. The impact 65 million years ago was so violent that nothing in human history could compare with it. The asteroid or comet that hit the earth at that time was about 6 miles wide. It rushed to the surface of the earth at a speed of more than 40 times the speed of sound. It is so huge that when it hits the earth, its front end has touched the ground, but its tail is still at an altitude of 35,000 feet, which is equivalent to the flying height of a jet airliner. What hit the earth was a boulder the size of a mountain. Volcanic eruption says that volcanic eruption is a volcanic eruption, spewing out a lot of carbon dioxide, causing the greenhouse effect of the earth and killing plants. Moreover, the volcanic eruption released a lot of salt, which broke the ozone layer, and harmful ultraviolet rays irradiated the earth's surface, causing extinction. Antonio Cikic, a famous Italian physicist, recently suggested that the extinction of dinosaurs was probably caused by a large-scale submarine volcanic eruption. Professor Qi Jichi believes that at the end of Cretaceous, a series of large-scale volcanic eruptions occurred on the earth under the ocean, which affected the thermal balance of seawater, and then caused the change of land climate, thus affecting the survival of dinosaurs and other animals that needed a lot of food to survive. His reason is that the impact of modern submarine volcanic eruption on the ocean and atmosphere is well known, but its impact is far less than that of submarine volcanic eruption 65 million years ago. Professor Qi Jichi believes that in the past, the scientific community knew very little about submarine volcanic eruption, and now it is necessary to conduct in-depth research on this phenomenon that seriously affects the earth's environment. For example, he said that Greenland once had dense vegetation, but when the global ocean water temperature balance changed, the cold ocean current changed direction and crossed Greenland, thus turning this big island into a land covered with snow and ice. This is a typical example that the change of ocean water temperature balance has a great influence on climate. Submarine volcanic activity is an important factor affecting the balance change of ocean water temperature. Therefore, Professor Zichichi believes that the change of ocean water temperature balance caused by large-scale eruption of submarine volcano should be taken as an important reference factor for studying dinosaur extinction. According to Robert Barker, when the ocean ebbs and the land borders each other, the creatures touch or influence each other, which leads to the extinction of some species. Kangaroos, for example, can live on the island continent of Oceania, but they will die if they meet other animals on the South American continent. In addition to this relationship between eating and being eaten, there are also problems of infection and spread of diseases and parasites, and dinosaurs may become extinct. Warm-blooded animals In the past, all scientists thought that dinosaurs were cold-blooded or warm-blooded animals like other reptiles, but with the increasing number of fossil data, people's understanding has also changed. Some people think that some dinosaurs may be warm-blooded animals. First of all, they think that some dinosaurs are extremely agile, and they don't crawl on the ground like snakes, but run on the ground with two hind legs, which can reach 20 to 90 kilometers per hour. This requires a strong heart and a high metabolism, which is obviously impossible for cold-blooded animals. Secondly, dinosaurs ate a lot. It is speculated that a 30-ton sauropod dinosaur may eat nearly 2 tons of food every day, and only warm-blooded animals need so much energy. From the point of view that carnivorous dinosaurs are far less than herbivorous dinosaurs, this is also reasonable. In addition, there are some smaller dinosaurs whose bodies are covered with a layer of feathers or hair, which is also to prevent the loss of body temperature. Other aspects, such as the study of bones, also preliminarily show that some dinosaurs were warm-blooded animals. As soon as the theory of warm-blooded dinosaurs was put forward, it was strongly criticized, but it is still difficult to reach a conclusion. Some people think that dinosaurs were warm-blooded animals, so they could not bear the cold climate in the late Cretaceous and could not survive. Because even if dinosaurs were warm-blooded, their body temperature was still not high, probably similar to that of living sloths, and to maintain such a body temperature, they could only live in a tropical climate. At the same time, the dinosaur's respiratory organs were not perfect and could not fully supplement oxygen. They don't have thick hair to avoid hypothermia, but they easily lose a lot of heat from their long tails and feet. The difference between warm-blooded animals and cold-blooded animals is that if the body temperature drops below a certain range, it will consume physical energy to raise the body temperature and the body will soon become weak. They are too big to go into caves to avoid the cold, so if the cold days last for a few days, they may freeze to death because of exhaustion. However, there is a doubt about this theory, that is, dinosaurs were not all that huge, and not all of them could hide in caves to take refuge. Therefore, this theory is not perfect. It is said that because of climate problems, cannibalism leads to the extinction of a large number of plants, leading to the gradual extinction of herbivores, while carnivores become crazy and kill each other because of lack of food. Doubt: Since the extinction of plants led to the extinction of dinosaurs, why did omnivorous dinosaurs that ate insects and so on also become extinct, while other animals were safe and sound? The number of dinosaurs in the oppression theory increased sharply, which led to the extinction of herbivorous dinosaurs with limited plants, and then carnivorous dinosaurs that ate herbivorous dinosaurs died because of lack of food. (Doubt: Why did dinosaurs suddenly increase after about 200 million years of ecological balance? The key to the establishment of this theory has also directly caused many scholars to discuss the reasons for the abnormal increase in dinosaur production. According to the theory of species aging, dinosaurs were too big because they flourished for more than 65.438+0.6 billion years. Moreover, bones such as horns are also extremely developed, which causes great inconvenience to life and eventually leads to extinction. The most representative confusing dragon among dinosaurs, with a body length of 25 meters and a weight of 30 tons, lost its viability because of its huge size. In addition, Triceratops and others also went to the road of self-destruction because of their expanding three horns and unusually developed bones to protect their heads. (Doubt: Not all dinosaurs are so huge, but there are also small dinosaurs with a body length of only about one meter. In addition, there are dinosaurs with bones like deer that can run briskly. But why did this dinosaur die out at the same time? Moreover, in cold-blooded animals, abnormally developed bones and other parts are considered to be able to absorb external temperature and release internal heat to regulate body temperature, which has very favorable functions. Therefore, I suspect that the extinction of dinosaurs was due to the aging of species. The theory of alkaloids holds that flowering plants began to appear in the last period of dinosaur prosperity, that is, the Cretaceous period, and some of them contained toxic alkaloids, and dinosaurs died of poisoning due to large intake. Because mammals can distinguish poisonous plants through taste and smell, but dinosaurs don't have this ability. However, plants containing alkaloids did not suddenly appear in the late Cretaceous, but were already visible five million years before the extinction of dinosaurs. This theory can't explain why dinosaurs survived during this period. So this statement cannot be established alone. The theory of reproductive frustration has found the egg fossils of ancient reptiles, especially dinosaurs in many parts of the world. According to the morphological structure, dinosaur eggs can be divided into short round eggs, oval eggs and long eggs. The size of dinosaur eggs varies greatly, including the eggshell thickness, internal and external "ornamentation", eggshell structure and the proportion of cone layer and columnar layer in its shell. In order to further study the internal characteristics of dinosaur eggs, scientists have adopted many new technologies and methods, such as scanning tunneling microscope, X-ray diffractometer, polarizing microscope and CT scanner. In recent years, Chinese scientists used CT technology to study the internal structural characteristics of dinosaur eggs unearthed in Laiyang, Shandong Province for the first time, and found that some dinosaur eggs in Laiyang, Shandong Province contained dinosaur embryos that could not be observed by other methods. According to the data obtained from deep-sea geological drilling, some scientists believe that the climate on the earth changed abnormally 65 million years ago and the temperature suddenly rose. This change makes the temperature-changing animals with weak heat dissipation ability, such as dinosaurs, unable to adapt to the environment well, resulting in the disorder of endocrine system in their bodies, especially causing serious damage to the reproductive system of male individuals. As a result, dinosaurs could not reproduce and eventually went extinct. There is also a theory that although sudden climate change led to the extinction of dinosaurs, the process of speculation is different. Scholars of this school believe that about 70 million years ago, the Arctic Ocean was completely separated from other oceans by land. In the last days, due to various factors, salty seawater gradually turned into fresh water. By 65 million years ago, the "bank" separating the Arctic Ocean from other oceans suddenly burst. A large amount of seawater from the Arctic Ocean is lightened by seawater desalination and flows into other oceans. Because the water temperature in the Arctic Ocean is very low, these "overflowing" cold water forms a layer of cold flow, which makes the seawater temperature in the oceans of the earth drop rapidly by about 20 degrees. The drop of ocean temperature has seriously affected the climate of the mainland, making the air over the mainland cold. At the same time, the water vapor content in the air has also decreased rapidly, resulting in a large area of drought on land. The comprehensive structure produced by these climate changes on land is the extinction of dinosaurs. One possible way for climate change to lead to dinosaur extinction is to seriously affect dinosaur eggs. Some scientists found that at the end of Cretaceous before the extinction of dinosaurs, the eggshells of dinosaur eggs became thinner, indicating that there was a role caused by rapid climate change before the extinction of dinosaurs. Some paleontologists in China have also found that among the dinosaur eggs produced in some fossil sites, there are fewer pores on the eggshells of dinosaur eggs near extinction than in other periods, which is probably related to the cold and dry climate. The extinction of dinosaurs at the end of Cretaceous is an eternal mystery in the history of biology. Scientists have put forward one theory after another to try to explain the reasons, but so far there is no acceptable conclusion. The popular saying is that the disaster caused by the asteroid hitting the earth led to the extinction of dinosaurs, but this theory is not perfect. Because dinosaurs were the most successful animals on earth at that time, their rich diversity was manifested in different sizes, shapes and lifestyles. If the disaster caused by asteroid impact led to the extinction of dinosaurs, then why did birds escape the disaster and survive? This has prompted people to look for other ideas to analyze the reasons for the extinction of dinosaurs. Modern scientific analysis tells us that in the distant age when the earth was just formed, there was basically no oxygen in the air, but the content of carbon dioxide was very high. Later, with the appearance of autotrophs, photosynthesis began to consume carbon dioxide and produce oxygen, thus changing the atmospheric environment on the earth. At the same time, on the one hand, carbon dioxide is deposited in the stratum in the form of coal and oil through biological fixation, and on the other hand, it is deposited in the form of various carbonates through organic or inorganic processes. This kind of evidence collection has been going on. There is evidence that the concentration of carbon dioxide in Mesozoic era in which dinosaurs lived was very high, but the concentration of carbon dioxide in Cenozoic era after that was very low. Is this change in atmospheric composition related to the extinction of dinosaurs? As we all know, every living thing needs a suitable environment to survive normally, and environmental changes can often lead to the rise and fall of a species. When the environment is beneficial to this species, it will flourish; Otherwise, it will decline or even become extinct. Environmental factors include temperature, water and other factors, as well as atmospheric composition. So, will the change of atmospheric composition affect the life span of living things? The answer is yes. For example, people's lives are in danger in an environment with high carbon dioxide concentration, and some animals are even more sensitive to the change of carbon dioxide concentration than people. In Mesozoic, the content of carbon dioxide in the atmosphere was high, indicating that dinosaurs adapted well to the atmospheric environment with high carbon dioxide concentration. Perhaps only in such an atmospheric environment can they live well. At that time, although mammals had appeared, they had not developed greatly. Perhaps because the environment such as atmospheric composition was not favorable to them, they were in a weak position and developed slowly in Mesozoic. With the passage of time, at the end of Cretaceous, the atmospheric environment changed greatly, the content of carbon dioxide decreased and the content of oxygen increased. This unfavorable environment may be reflected in two aspects: 1, the dinosaur's body became uncomfortable, and it was easy to get sick in the new environment, and the disease would spread like a plague. 2. The new atmospheric environment is more suitable for the survival of mammals, and mammals have become more advanced and adaptable competitors. Under the action of these two factors, dinosaurs finally became extinct. And those reptiles that are left behind are a few reptile species that can adapt to both the old environment and the new environment. The theory that the change of atmospheric composition led to the extinction of dinosaurs has two starting points. One is that the atmospheric composition of Mesozoic is different from that of modern times. Modern science has proved this. The other is that every living thing needs a suitable atmospheric environment to survive. Modern science is not difficult to verify this. There was almost no oxygen in the ancient atmosphere, but the content of carbon dioxide was high. Later, due to the appearance of organisms, the process of carbon dioxide content gradually decreasing and oxygen content gradually increasing in the atmosphere under photosynthesis may explain many phenomena in the history of biological evolution. For example, the explosion of life in CAMBRIAN is also a mystery in evolutionary history. The change of atmospheric composition can also explain this, because animals can't directly use inorganic substances for photosynthesis, and its origin lags behind that of plants, and it will only happen when the oxygen content in the atmosphere reaches a certain level. Therefore, the outbreak of CAMBRIAN life must be guaranteed by the fact that the oxygen content in the atmosphere reaches a certain level, which has been proved by science. So the impact of asteroids may have played a role in the extinction of dinosaurs, but it does not seem to be the most critical factor. In addition to the above 22 famous sayings, there are many little-known sayings (such as sunspot eruption, electromagnetic disturbance, changes in the direction and intensity of the earth's magnetic field). As for which is the best, everyone has different opinions, and there is no right or wrong. After all, the mystery of dinosaur extinction has not really been solved!