Biological extinction is also called biological extinction. It is not always uniformly speedy and gradually progresses. There are often large-scale cluster extinctions, that is, mass extinctions of organisms. The whole family, the whole order and even the whole class can completely disappear in a very short time or only a very small number of remaining. During the cluster extinction process, all species in the entire taxa are often all the species in the entire taxa. No matter its status in the ecosystem, they cannot escape this disaster. Moreover, many different biological groups often extinct together, but some groups always survive, and some groups are born or began to flourish. Large-scale cluster extinctions have a certain periodicity, which happens once every 62 million years, but cluster extinctions of absolute animals have the greatest impact, while cluster extinctions of terrestrial plants are not as significant as animals.

The first mass extinction of organisms was in the late Ordovician period 440 million years ago. The event caused the extinction of about 85% of species, also known as the first mass extinction of species: the Ordovician mass extinction.

Introduction to Ordovician

The Ordovician Period (Ordovician Period, Ordovician), a geological name, is the second period of the Paleozoic era, which began 500 million years ago and lasted 65 million years.

The Ordovician period is also divided into three generations: early, middle and late. The Ordovician period is one of the most extensive periods of Shanghai's invasion in the history of geography. In the platform area inside the plate, seawater is widely distributed, manifested as the general development of coastal shallow marine carbonate rocks. In the active trough area at the edge of the plate, it is a deeper water environment, forming shallow sea, deep-sea clastic sedimentation and volcanic eruption sedimentation.

There was a large-scale ice age in the late Ordovician period, with distribution ranges including Africa, especially North Africa, Argentina in South America, Bolivia in Europe, Spain and southern France.

Source of the word "Odovician"

The term "Ordovician" was proposed by British geologist C. Lapworth in 1879. It represents the rock formation exposed from the Arenig Mountains in the United Kingdom and crosses North Wales to the east, and is located between the Cambrian and Silurian rock formations. This area is the residence of the Ordovician tribe, so it is named.

Ordovician biological evolution

At that time, the climate was mild and the shallow sea was spread wide. Many parts of the world (including most parts of our country) were covered by shallow sea water. Marine organisms developed unprecedentedly.

In the vast ocean of the Ordovician, marine invertebrates flourished unprecedentedly, and a large number of various invertebrates live in. In addition to the groups that began to flourish in the Cambrian period, some other groups have also been further developed, including pyramid, coral, brachiopod, sea lilies, bryozoos and molluscs.

Bistone is the most peculiar group of marine animals in the Ordovician period. They have flourished and widely distributed since the early Ordovician period. During this period, brachipods evolved rapidly, and most of the groups have appeared. The chitin-shelled brachipods gradually declined, while the calcified shells have become popular for a while. Nautilus entered its prosperous period, and their bodies were huge and were ferocious carnivorous animals in the ocean at that time. Due to the emergence of a large number of carnivorous nautilus, trilobites evolved into many defensive needles in the chest and tail to avoid attack or devouring of carnivorous animals. Corals have appeared in large numbers since the Middle Ordovician period. Although the corals in the complex are still relatively primitive, they can form small reefs.

In the late Ordovician period, about 480 million years ago, the first reliable terrestrial vertebrates - freshwater jawless fish - appeared; freshwater plants are probably also seen in the Ordovician.

The first mass extinction occurred in the late Ordovician period 440 million years ago. Due to the colder climate and the decline of sea levels on Earth, various invertebrates living in water bodies disappeared.

At the end of the Ordovician period 440 million years ago, it was the largest species extinction event in the history of the earth, with about 85% of species extinctions. Paleontologists believe that this species extinction was caused by global climate cooling. About 440 million years ago, the current land where the Sahara was located was once located in the Antarctic. When land gathers near the poles, it is easy to cause thick ice accumulation - this is the case in the Ordovician period. Large areas of glaciers cool the ocean currents and atmospheric circulations, the temperature of the entire earth dropped, the glaciers locked in water, and the sea level also decreased, and the original rich coastal ecosystem was destroyed, resulting in 85% of the species extinction.

The second extinction of creatures

Time: The late Devonian period 365 million years ago.

Event: Marine creatures suffered a catastrophe.

Also known as: the second species is extinct and the Devonian extinction.

Introduction to Devonian

The Devonian period, the name of the geological age, was the fourth Paleozoic period, which began about 405 million years ago, ended about 350 million years ago, and lasted about 50 million years.

The Devonian is divided into three generations: early, middle and late, and the strata are divided into three groups: lower, middle and upper. The paleogeographic appearance of the Devonian period has undergone tremendous changes in the early Paleozoic period. It is manifested as the expansion of land area, the development of terrestrial strata, and the appearance of the biological world has also undergone tremendous changes. Land plants and fish-shaped animals have developed unprecedentedly, amphibians have begun to appear, and the composition of invertebrates has also changed significantly.

Fish Land Age

The Devonian is a period of vertebrates flying and development. Fish are quite prosperous and various types of fish appear. Therefore, the Devonian is called the "Era of Fish". The most important thing is the emergence of the ancestors of amphibians and reptiles, the ancestral figure of amphibians and reptiles.

Research on paleo-climates shows that the Devonian period was warm. Fossil records show that the temperate climate was as far away as the Arctic. The second mass extinction occurred in the late Devonian period, and the reason for the earth's climate became colder and the retreat of the ocean.

In the late Devonian period about 365 million years ago, it experienced two peaks, with a gap of 1 million years between them. It was the fourth largest species extinction event in the history of the earth, and marine life suffered severe damage.

The third extinction of creatures

Time: The end of the Permian period 250 million years ago,

Event: Causing more than 95% of Earth's creatures extinction.

Also known as: the third mass extinction of species and the Permian mass extinction.

Introduction to the Permian

The Permian period is the last period of the Paleozoic and an important coal-forming period. The Permian period is divided into the Early Permian, Middle Permian and Late Permian. The Permian began about 295 million years ago and extended to 250 million years, and experienced a total of 45 million years. The Permian crustal movements were relatively active, and the relative movements between old plates intensified. Many troughs around the world were closed and folded mountain systems were formed one after another. The old plates gradually spliced ​​together to form a joint Paleocontinent (pan-continent). The further expansion of land area, the reduction of ocean range, and the changes in the natural geographical environment promoted the important evolution of the biological world and herald the arrival of a new era in the history of biological development.

The worst mass extinction event ever occurred in the late Permian period about 250 million years ago. It is estimated that 96% of species on the earth have become extinct, of which 90% of marine organisms and 70% of terrestrial vertebrates have all disappeared. Trilobites, sea scorpions and important coral groups have all disappeared. The terrestrial monoarch groups and many reptile groups have also become extinct. This mass extinction caused the major organisms that occupied the ocean for nearly 300 million years to decline and disappear, giving way to new biological species, and the ecosystem has also received the most thorough update, paving the way for the evolution of reptiles such as dinosaurs. The scientific community generally believes that this mass extinction is a milestone in the turning point of the earth's history from Paleozoic to Mesozoic. The decline in marine species caused by other mass extinctions is less than 1/6, and it has not caused such a major turning point in the biological evolution process.

Scientists believe that sea level decline and continental drift occurred in the Permian period, which caused the most serious mass extinction of species. At that time, all continents gathered into a united ancient continent, the rich coastline decreased sharply, the continental shelf also shrunk, and the ecosystem was severely damaged, and the extinction of many species was due to the loss of living space. What's more serious is that when the shallow continental shelf was exposed, the organic matter originally buried on the seabed was oxidized, and this process consumed oxygen and released carbon dioxide. The oxygen content in the atmosphere may be reduced, which is very unfavorable to animals living on land. As the temperature rises and sea level rises, many land organisms were hit by disasters, and the oceans became hypoxic zones. The large amount of organic matter-rich shale deposited in the strata is a proof of this disaster.

This mass extinction was caused by a series of reasons such as climate change, expansion of desert scope, and volcanic eruptions.

Meteorite impact

Some scientists believe that the impact of meteorites or asteroids on Earth led to mass extinctions of organisms in the late Permian period. If this impact reaches a certain level, it will produce a devastating shock wave around the world, causing climate change and organisms to die. Some recent evidence has attracted attention to this view. But most biological scientists believe that the extinction was caused by natural changes on Earth.

Climate changes

Some scientists believe that climate change is the main cause of this catastrophe. Because rocks formed at the end of the Permian period showed that the climate in some areas became colder at that time, forming ice caps at the poles of the earth. These huge white ice caps emit sunlight back to space, which will further reduce global temperatures and make it difficult for organisms on land and sea to adapt. If the plane drops in Shanghai and volcanic eruptions are added, this will become a catastrophe.

Changes in atmospheric composition

Some biologists believe that animals with more active and active lifestyles, such as mammalian monoarchers, need more oxygen than other animals, may become extinct due to changes in atmospheric composition. Because the decrease in temperature in the late Permian period will lead to a drop in sea level. The vast coal seam area of ​​the seabed will be exposed, releasing a large amount of carbon dioxide into the atmosphere, and the oxygen content in the atmosphere will be relatively reduced.

Volcanic activities

The volcanic eruption returns to spew a large amount of gas and volcanic dust into the atmosphere. Volcanic ash clusters will not only suffocate animals to death, but may also block the sun and reduce global temperatures. Therefore, volcanic activity may also be one of the causes of the extinction incident in the late Permian period. Siberia once discovered the material emitted by the violent eruption of volcanoes at that time.

The raging desert

The Permian land blocks collided and bordered to form the huge Pangu continent. Rain and fog from the sea could no longer penetrate into the inland areas. As a result, some areas of the Permian became drier and hotter, causing the desert to grow wider and wider, and animals that could not adapt to the arid environment became extinct.

The fourth extinction of creatures

Time: The late Triassic period 200 million years ago.

Event: The fourth biological extinction occurred, and reptiles suffered severe damage.

Also known as: Triassic extinction, the fourth species extinction

Introduction to the Triassic

The Triassic period was the first period of the Mesozoic era. It is located between the Permian and Jurassic.

It began between 250 million and 203 million years ago and lasted about 50 million years. After the Haixi Movement, many troughs were converted into mountain systems, the land area expanded, and some inland basins were produced in the platform area. This new paleogeographic condition led to changes in sedimentary facies and biological worlds. Since the Triassic period, terrestrial facies were deposited all over the world, especially in China and other parts of Asia. In terms of paleoclimate, the early Triassic period inherited the characteristics of drought in the late Permian period; after the middle and late periods, the climate transitioned to damp heat, resulting in the phenomenon of red rock formations containing coal, and drought-prone plants developing to damp heat plants. Plant geographical areas also diverged at the same time.

The extinction of marine life

At the end of the Triassic period 195 million years ago, it was estimated that 76% of the species, mainly marine organisms disappeared during this extinction. This disaster was not particularly obvious. It was only found that sea level rose again after it fell, and large areas of hypoxic seawater appeared.

The fifth extinction of creatures

Time: around 65 million years, late Cretaceous

Event: Suddenly, the dinosaurs that have dominated the earth for a long time since the Jurassic have become extinct.

Also known as: the fifth mass extinction of species, the Cretaceous mass extinction, the dinosaur mass extinction

Introduction to the Cretaceous

The Cretaceous Period (Cretaceous Period, Cretaceous) was the last period of the Mesozoic Period. The Cretaceus Period was the last period of the Mesozoic Period, which began 137 million years ago and ended 65 million years ago, and 70 million years later. Both the inorganic and organic realms underwent important changes during the Cretaceous Period. It is located below the Jurassic and above the Neozoic Region. The Cretaceous Period was the period when the Earth's surface was most submerged in the Mesozoic Region. During this period, the Cretaceous layer was widely deposited in the northern hemisphere. In 1822, Belgian scholar J.B.J. Omalidaruy named it the Cretaceous System. The Cretaceous layer is a very fine and pure powdery limestone, which is a marine deposition of biological origin. It is mainly composed of a calcium ultrafine fossil called quartz algae and a planktose foraminifera fossil.

The end of the dinosaur era

At the end of the Cretaceous period 65 million years ago, it was the second largest biological mass extinction event in the history of the earth, with about 75%-80% of species extinctions. Among the five mass extinctions, this mass extinction event was the most famous, and it was famous for the end of the 140 million-year-old dinosaur era, and the ammonites in the ocean also disappeared. Its greatest contribution was to eliminate the dominant dinosaurs and their similarities on the earth, and provided an opportunity for the final appearance of mammals and humans. This disaster came from the Earth.

External space and volcanic eruptions, one or more meteorite showers that occurred at the end of the Cretaceous period caused the collapse of the global ecosystem. The impact caused a large amount of gas and dust to enter the atmosphere, so that the sun could not penetrate, and the global temperature dropped sharply. This black cloud covered the earth for several years (to several million years to several thousand years). Plants could not obtain energy from the sun. Algae and scattered forests in the ocean gradually died, the basic links of the food chain were destroyed, and a large number of animals died of starvation, including dinosaurs.

Asteroid impact theory

Scientists supporting the asteroid impact theory infer that this impact is equivalent to 1 million times the strongest earthquake in human history, and the explosion energy is equivalent to 10,000 times the total explosion of nuclear weapons on Earth, causing 21,000 cubic kilometers of matter to enter the atmosphere. Due to the high-density of dust in the atmosphere, the sunlight cannot shine on the earth, causing the temperature of the earth's surface to drop rapidly. Without sunlight, plants gradually wither and die; without plants

, Plant-eating dinosaurs also died of hunger; without plant-eating animals, carnivorous dinosaurs also lost their food source, and they slowly died in despair and killing each other. Almost all large terrestrial animals were unable to survive and died in despair in cold and hunger. Small terrestrial animals, like some mammals, barely survived the most difficult time, and waited for the Paleogene terrestrial vertebrates to prosper again.

Supporters of the impact hypothesis have found many powerful evidence to prove their views. The most powerful evidence comes from the iridium anomalies and impact quartz found on the geological boundary of K/T (Cretaceous and Paleogene). Scientists speculate that this high-content iridium element was brought by the asteroid that hit the earth. The impact quartz was formed during the impact, but the impact craters formed by the impact were not found. Most craters are believed to be of inconsistent with the speculation.

American Chattergi proposed a similar hypothesis about 10 years ago. He believed that the murderer who hit the Earth at the end of the Cretaceous period was not an asteroid or meteorite, but a comet shower. A large number of comet showers hit the Earth, forming an impact belt around the Earth, and two huge comet bodies became the "main culprits" of the dinosaur mass extinction: one formed a huge crater near the Gulf of Mexico, which we are familiar with, and the other hit the current Indian continent, forming a crater larger than the crater near the Gulf of Mexico.

The upcoming sixth biological extinction

Since the emergence of humans, especially after the Industrial Revolution, humans have only noticed the practical value of specific biological sources and developed them wantonly, while ignoring the indirect and potential value of biodiversity, which has caused the Earth's life-sustaining system to be ruthlessly eroded by humans. Scientists estimate that without human interference, an average of 90 species of vertebrates will be extinct every 100 years in the past 200 million years, and an average of one higher plant will be extinct every 27 years. In this context, human interference has increased the extinction rate of birds and mammals by 100-1000 times. Since 1600 years,

724 species of higher animals and plants have been extinct. Most species have become extinct before humans know it. According to rough estimates, in 400 years, the environmental area of ​​living organisms has been reduced by 90%, and the species has been reduced by half. Among them, the impact of the deforestation of tropical rainforests on species losses is more prominent. It is estimated that the extinction of species caused by deforestation of tropical forests from 1990 to 2020 will reduce the number of species in the world by 5%-15%, that is, 50-150 species per day. In the past 400 years, a total of 58 mammals have been extinct around the world, and one species has been extinct every 7 years.

This speed is 7-70 times higher than the normal fossil record; in the 100 years of the 20th century, a total of 23 mammals were extinct worldwide, and one species was extinct every 4 years, which was 13-135 times higher than the normal fossil record... The following is a set of latest data from the State Administration of Environmental Protection: There are 1,000 rare and endangered species in China, 28 extremely dangerous species, and 7 extinctions or may be extinct; 63 endangered and threatened gymnosperms, 14 extremely dangerous species, and 1 extinction; 433 vertebrates are threatened, and 10 extinctions and possibly extinctions.... Biodiversity is the most common in history
Chapter completed!