The earth has experienced five mass extinctions in its 4.6 billion year history? What is the reason?

4.6 billion years ago, the earth was born in the newly formed solar system. The early Earth was not beautiful, nor was it a planet of life, but the earth was in a very good position, in a livable zone, with the sun’s temperature and sunshine. At this time, the earth did not have liquid water. Not long after, a group of Exodus came to the solar system, which was still in a chaotic state. They were a large number of comets and asteroids.

Comets and asteroids impact on the earth, bringing a lot of liquid water to the earth, so that the earth’s ecosystem has a preliminary structure, asteroid impact has brought a variety of rich mineral resources to the earth. At the same time, comets may also bring the seeds of life. After hundreds of millions of years, the solar system has stabilized and the earth’s ecological environment has gradually improved. At this time, the earliest single cell life appeared.

Simple life has evolved step by step to form a species rich biota, and the earth has finally become a real life planet. However, the evolution of life on the earth is not smooth. I believe many friends know that the earth has experienced five mass extinctions in its history, each of which basically wiped out most of the organisms. Finally, after a long period of evolution, new species of life emerged and ushered in mass extinction again. So what are the reasons for the five mass extinctions? Next, we will explore and analyze them.

The first mass extinction occurred at the end of the Ordovician period 440 million years ago, also known as the Ordovician mass extinction. This extinction event led to the extinction of about 85% of species. At this time, marine life is very prosperous. It’s easy to understand that water is the source of life. The earliest life on earth was born in the ocean, and terrestrial life evolved from marine life.

So what is the cause of the mass extinction? Paleontologists believe that the global climate is getting colder. About 440 million years ago, the Sahara desert is now located in the South Pole. When it is close to the south pole, it is easy to form a thick ice layer, just like the Ordovician period. Large glaciers cool ocean currents and atmospheric circulation. The temperature of the whole earth has dropped, glaciers have locked up water, and sea levels have fallen.

This situation is what we call the ice age, and it is also the big ice age. The small ice age usually lasts for only a few decades, and its impact is limited. But the great ice age is different. It makes the temperature of the earth lower, and it lasts for a long time, possibly tens of millions of years. So every time the great ice age happens, it’s a time when life is facing a huge disaster.

The second mass extinction occurred in the late Devonian period 365 million years ago, also known as the Devonian mass extinction. During this period, the land area began to expand, and a large number of terrestrial organisms began to evolve. In particular, vertebrates ushered in a period of rapid development, and reptiles also began to appear. The extinction event led to the extinction of 70% of the earth’s species.

The second mass extinction event mainly affected marine life, but the impact of terrestrial plants and animals was much smaller. After this extinction event, terrestrial life really ushered in a period of rapid development. The cause of the extinction is still unclear. Some scientists believe that it is caused by the rapid change of global climate, while others believe that it is the super volcanic eruption caused by asteroid impact.

The third mass extinction occurred at the end of Permian 250 million years ago, also known as the Permian mass extinction, which is the most serious mass extinction event in history. If you want to ask which of the five mass extinctions is the most serious, it must be the third. According to statistics, the extinction event led to a 52% reduction in the number of biological families and a more than 90% reduction in the number of species. The greatest impact on marine life, 96% of marine species are extinct, leading to the reduction and disappearance of the number of major organisms, including trilobites, occupying the ocean for nearly 300 million years.

On land, more than three-quarters of vertebrates have disappeared, and lizards, amphibians and theropods have declined dramatically. Scientists believe that the cause of this mass extinction may be that the earth once experienced sea-level decline and continental drift. At this time, all continents gathered into a united ancient land. Many organisms lost their living space, and the oxygen in the atmosphere also decreased sharply. Plate movement caused abrupt climate change, expansion of deserts and large-scale volcanic eruptions.

Some scientists believe that the mass extinction may be related to the gamma ray bursts generated by the supernova explosion. For example, the decrease of ozone and oxygen in the atmosphere during this period may be caused by cosmic ray irradiation. Although the third mass extinction was very serious and almost wiped out all the earth’s creatures, the spring of reptiles came after the disaster. A huge creature that ruled the earth for 160 million years appeared. It was dinosaur.

The fourth mass extinction occurred in the Late Triassic period 208 million years ago, also known as the Triassic mass extinction. The scale of this extinction is relatively small, with only 25% of species on the verge of extinction, mainly marine organisms. The extinction also created many favorable conditions for the rule of dinosaurs, from which dinosaurs began their long journey to rule the earth. Scientists believe that the mass extinction may be related to asteroid impact on the earth and super volcano eruption.

We are familiar with the fifth mass extinction. It was the Cretaceous mass extinction that happened 65 million years ago. This mass extinction event resulted in the overall collapse of the dinosaur family, and about 80% of the species on the earth went extinct.

There are various explanations for the disaster, one of which is generally accepted by the scientific community as an asteroid impact. At the end of the Cretaceous, one or more meteor showers led to the collapse of the global ecosystem. A lot of gas and dust enter the atmosphere, so sunlight cannot penetrate, global temperature drops sharply, dark clouds cover the earth for several years, plants cannot get energy from the sun, marine algae and land forests gradually die, the basic link of the food chain is destruction, many animals die of hunger, including dinosaurs.

After the fifth mass extinction, the reign of dinosaurs came to an end. At the same time, it opened the door for the emergence of mammals and human beings. From then on, mammals ushered in great development, and human primitive life also appeared. Maybe many people think that human beings were born only for millions of years. In fact, it is not. Millions of years actually refers to the time when human beings began to evolve their wisdom.

The earliest form of human life may have appeared tens of millions of years ago, that is, shortly after the fifth mass extinction. At that time, the earliest form of human life appeared. Through step-by-step evolution, it finally went to the road of intelligent evolution, and gradually appeared modern human. The emergence of any life can not be produced out of thin air, it must have its roots, and so is human nature.

Through the five mass extinctions in the history of the earth, we seem to find that each mass extinction is a sublimation of life, and the purpose may be the ultimate birth of intelligent human beings. Now that human beings are born, will the earth usher in the sixth mass extinction in the future? It’s hard to say, and I believe scientists can’t predict it.

The occurrence of mass extinction is basically caused by some factors that lead to dramatic changes in the earth’s ecological environment. Some people think that if the sixth mass extinction occurs in the future, it may be caused by human beings themselves. The reason is that the rapid development of human science and technology and the failure to protect the earth make the earth’s environment worse and worse, and the earth’s ecological system must have a limit to bear Once this limit is exceeded, the ecosystem will collapse completely, and the earth will face mass extinction again.

Of course, if the sixth mass extinction really happens in the future, most of the creatures on the earth may be extinct, but human beings may survive. The reason is that at that time, human science and technology may have been very developed, and interstellar migration has also been realized. When the earth can’t survive, we can go to other planets to survive, and we don’t have to worry about the disappearance of human beings.

Guys, do you think the sixth mass extinction will happen? Welcome to leave a message below to discuss and express your opinions.

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