The idea that species no longer exist is contrary to theology, which makes it difficult for many people to accept.But before the end of the 18th century,naturalistWe began to agree thatEarth historyThe extinction of species has occurred many times.Extinctive beasts, especially those once wandering around the earthdinosaurAnd other huge beasts.The fossils left by them make people dumbfounded.DarwinSouth AmericaThe fossils of several "extinct monsters" were excavated.He is《Origin of species》I think no one is more surprised by the extinction of species than I am
Extinction process
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Bone specimen
Some scientists believe that species extinction has always been a part of the process of life.University of ChicagopaleontologistDavid M. Raup estimates.Ninety nine percent of previously surviving species have become extinct.In the 1980s, Loup and his colleague Jack Sepkoski made a detailed and in-depth studyFossil recordLater, the research results on the "background" ratio of species extinction were published, namelyOrganismOn EarthLife historyThe normal proportion of extinctions.The fossil record shows that the species has experienced at least five mass extinction or extinction;From the geological point of view, in a very short time.The rate of extinction has risen sharply.According to Laup's research, the largest extinction of species occurred about 225-245 million years ago, and the number of extinct species accounted for 96% of the surviving species.Three quarters of all species, including the last generation of dinosaurs, disappeared in the extinction 65 million years ago.For these mass extinctions, scientists have put forward many theories.Some scientists believe that the reason is that whenContinental plateWhen drifting from the tropics to the poles,global climateChanges that have occurred.Some scientists claim that large-scaleAsteroidsperhapsComet clusterCollision with the Earth, resulting in worldwideDust cloud, blocking the sun, causing the temperature to drop, leading to the extinction of species.geologistHeguOrnithologistStill looking for evidence for these and other theories.Extinction andSpecies evolutionClose relationship.Darwin's discovery about species andLife formsThe relationship between replacement stages and the fossils of extinct species is a wonderful explanation.Darwin also realized that the emergence of new species was closely related to the extinction of existing species.With regard to species extinction and its role in species form (formation of new species),theory of evolutionBiologists continue to offer new ideas.One of the most influential ideas comes fromHarvard UniversityStephen Jay Gould andAmerican Museum of Natural HistoryNiles Eldredge.Their discontinuous balance theory believes that in the process of species evolution, there will be short-term sharp changes every longer period of stability;At that time, some species became extinct and some new species appeared.That is to say, in about several million years, after a certain number of species become extinct, drastic changes will occur, and species extinction provides enough evolutionary space for new species.
The earth is in another great extinction of species,asteroidIt is not the cause of this extinction.The contemporary mass extinction is the result of the activity of a very perfect species, Homo sapiens (the scientific name of modern man).becausehabitatDamage, environmental pollutionmodern industryAs a result of the rapid population growth, dozens of animals and plants are extinct every day.Perhaps in the millions of years that followed, the mass extinction of species provided room for the development of new species.However, when a species dies, it will never reappear.
Extinction speed
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britainecologyAnd a research team led by Jeremy Thomas of the Hydrology Research Center《science》Britain published in the magazinewild animalinvestigation reportIt said that in the past 40 years, the number of native bird species in Britain has decreased by 54%Wild plantThe variety has decreased by 28%, while the localbutterflyThe number of species decreased by an astonishing 71%.It has always been considered that there are many kinds and quantities with strong resilienceinsectAnd began to face the fate of extinction.
According to statistics, 75 species are extinct every day in the world, and 3 species are extinct every hour.
Extrapolate the survey of butterflies in Britain to other insects in Britain and the whole earthinvertebrateThen we are obviously experiencing a seriousbio-diversityCrisis.
A species is one that can mate with each other to produce fertile offspringNatural group。Extinct species refer to species that have not been found in the wild for sure in the past 50 years."The extinction is not just the extinction of a species, but many speciesGeological history periodThat is to say, it became extinct in hundreds of thousands of years, or millions of years. "Dr. Jiang Zhigang said.Thomas said, "InsectsSpecies quantityThey account for more than 50% of the global species, so their large-scale extinction of the earth's biodiversity is a bad news. "Since the Industrial Revolution, there have beenIcelandGreat auk、passenger pigeon 、South AfricaZebra donkeyIndonesiaBalinese tigerAustraliaWombat、Zhili Macaque、High nosed antelope、equus przewalskii And other species no longer exist.World Conservation UnionThe Red List of Threatened Species released shows that in 2009, there were still 1/4mammalMore than 1200 birds and more than 30000 plants are in danger of extinction.
Extinction causes
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Natural causes
Since 600 million years agomulticellular organismSince its birth on the earth, the mass extinction of species has occurred five times.
It happened about 250 million years agopermianThe third mass extinction at the end of the period wasEarth historyIt is estimated that 96% of the species on the earth are extinct, 90% of the marine life and 70% of the landvertebrateExtinction.the triassic periodTriassic period began 250 million to 203 million years ago and lasted about 50 million years.It is the first period of the Mesozoic Era.It is located in the Permian andjurassic period(Jurassic),Hercynian movement Later, manyGeosynclineTransformed into mountains, the land area expanded,Platform areaSomeInland basin。This new ancientgeographical conditions causesedimentary faciesandBiosphereChanges.The Triassic isthe paleozoic eraBiotaModern biota began to form after extinctionperiod of transition。In the early Triassic, most plants were drought tolerant. As the climate changed from semi dry and hot to warm and humid, plants tended to flourish,Low hill gentle slopeThe distribution is similar to modernEvergreen tree, such as looseCycasAnd the mainFloraAlmost completely extinct.During the Triassic, vertebrates were further developed.Among them,Grooved teethReptiles appeared and the earliest dinosaurs developed from them,Late Triassic ，Saurischia andOrnithialesThere are many kinds of dinosaursecosystemOccupies an important position.Therefore, the Triassic is also known as "the dawn before the generation of dinosaurs".At the same time, fromtherapsids The earliest mammal has evolved among reptiles -Mammalian Reptiles, but then fromjurassic periodFor more than 100 million years in the Cretaceous period, these untimely mammals had been living in the shadow of reptiles dominated by dinosaurs until the Cenozoic.
The fourth time happened 185 million years ago, 80% of reptiles became extinct.
The fifth time happened in the Cretaceous period 65 million years ago, which is also known to all. It ruled the earth for 160 million yearsDinosaur extinctionHas.
The first five mass extinction events were mainly caused by geological disasters and climate change.For example, the first mass extinction was caused byGlobal climate coolingAs a result, the last time in the Cretaceous was due to the collapse of the global ecosystem caused by the asteroid hitting the earth.
People are the culprits
The sixth mass extinction in progress has made mankind the culprit.Experts believe that it is hard to say whether human beings will be included.Some people do not deny that fromtheory of evolutionFrom the perspective ofnatural law, such aspandaThe population is in a state of decline.But since the emergence of human beings, especiallyindustrial revolutionSince then, the population of the earth has been increasingMeans of subsistenceMore and more, humanScope of activitiesMore and more disturbance to nature.In this way, a large number of forests, grasslands, and rivers have disappeared, and roads, farmland, and reservoirs have replaced themhuman activityThe traces of the broken into pieces."Every road is an insurmountable barrier for animals. Even butterfly populations on both sides of the road have been isolated, and they are no longer flying around like beforeGene exchange。”Dr. Jiang Zhigang said sadly, "Not to mentionTibetan antelopeSheeplion、tigerWait for such a big animal. "Some scientists estimated that in the past 200 million years, 90 vertebrates would be extinct every 100 years on average, and one vertebrate would be extinct every 27 years on average, if there were no human interferencehigher plantExtinction.But because of human interference, birds andMammalsThe speed of extinction has increased by 100 to 1000 times.U.S.ADuke University Stuart Pimm, a famous biologist, believes that if species decrease at this rate, one quarter to half of the species will be extinct or endangered by 2050.
New speciesDifficult to produce.Existing species are declining, but new species are hard to produce.according toFossil recordEvery time a species goes extinct, it is replaced by some new advanced groups.Dinosaur extinctionThe rapid reproduction of mammals is a typical example.Creatures are always evolving, and the creatures we see are evolved over a long period of time.Therefore, the generation of new species takes a long time and a lot of space, but it is under the management of people everywhere,natural environmentAs things get worse and worse, organisms lose the environment and conditions for natural evolution, and species continue to die naturally, but it is difficult for new species to emerge.Just like a tiger, if you give it enoughliving spaceIf it is allowed to hunt freely, it may also evolve to produce a new species similar to a tiger, but the space for its activities is limited, so it is difficult for it to survive, let alone evolve.Surface of the earthIt is composed of all living species such as animals, plants and microorganisms and their survivalEnvironmental compositionA hugebiosphereHuman beings are also one of them.A large number of creatures disappeared in the sixth mass extinction, but it is difficult to generate new species like the previous five. The Earth's ecosystem is far more fragile than imagined. When it is damaged to a certain extent, it will lead to the collapse of the system on which human beings rely for survival.
Extinction prediction
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Amazing speed
From EuropeAustralia, Central SouthAmericaandAfricaAfter a two-year study on the six regions with the richest biological species in the world accounting for 20% of the earth's surface area, scientists from.They predict that 1 million species will become extinct in 2050.According to the research of scientists, since climate warming is a fait accompli, the extinction of one tenth of the species to be extinct will be irreversible.But since then, countries have controlled the worldHarmful gasEmissionsOur efforts will be able to save more species from the same fate.
Alpine organism
Extinction of species
Alpine creatures have a good chance of survival.According to the research results of scientists, those living in high mountain areas are more likely to survive than other areas, because the species in this areaglobal warmingIt can move to higher and cooler areas.Those living in flat areas, such asBrazil、MexicoAnd Australia, their future living environment will be very fragile.In order to adapt to the changed climate and environment, the creatures in these areas can only move thousands of miles away, which is almost impossible.
Bird species
Birds are most likely to survive.In theory, birds are one of the most promising species to survive by virtue of their strong migration ability.In order to find more suitable areas for survival, birds can fly long distances, but because of the forest and othernatural conditionThey may not be able to find a natural environment that is truly suitable for survival.The result is that we can only face death.abovescientific researchOne of the team members, from the UKLeeds UniversityProfessor Thomas, an expert in biological protection, said: "When scientists conduct scientific research, they all hope to come to a clear conclusion.
Butterfly insect
Australia's 12 butterfly species will disappear.Other amazing discoveries made by scientists are that half of the 24 butterfly species included in the study in Australia will disappear forever in the coming years.
In South Africa's main biological reserves, 60% of the protected biological species are in danger of extinction.InMidwest BrazilSavannaThe research shows that more than 70% of the 163 trees in the region are extinct.Many of these plants are unique to the region.
Europe
Europe was the least affected.Europe's natural environment is affected byGlobal climate changeThe area with the least impact.The survival probability of animals and plants in this area is greater than that of animals and plants in large regions of the world.But even so, under the influence of climate warming, a quarter of birds and 11%~17% of plants in Europe will gradually become extinct in the future.Studies in Mexico show that animals and plants in plains and arid areas are most affected by climate warming.Once there is a slight change in the climate, these animals and plants need to move to far areas to find a new environment suitable for survival.In the regionAccept researchOf the 1870 species of animals and plants, one third will have a survival crisis in the future.
Climatic factors
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"Gender imbalance theory" According to the popular view in the scientific community, the extinction of dinosaurs is foreignCelestial impactCaused by the earth.However, there are different opinions on what kind of consequences caused by the impact of foreign celestial bodies directly accelerated the extinction of dinosaurs.For example, a new view put forward by British and American researchers is that the climate cooling caused by the impact of foreign celestial bodies may result in more males and less females of dinosaur offspring, and dinosaurs will eventually become extinct due to "gender imbalance".britainLeeds UniversityProfessor David Miller and colleagues pointed out in the new issue of Fertility and Sterility magazine that mammals, birds, snakeslizardAnd somefishThe sex of their offspring is determined by chromosomes or genes.Taking mammals as an example, the offspring who inherit two X chromosomes are female, and one X chromosome and one X chromosome are inheritedY chromosomeIt will be male.But some reptiles living on the earth, such ascrocodileandtortoiseWait, the eggs they laid areambient temperatureWill affect the gender of offspring.The researchers said that the sex of the offspring of some extinct species such as dinosaurs may also be determined by the temperature at the time of incubation.Miller et al. believed that the impact of foreign celestial bodies on the Earth about 65 million years ago was likely to cause a large amount of dust to enterEarth's atmosphereAs a result, the global climate became colder, which led to the male occupation of the descendants of dinosaursleading role 。This imbalance in gender ratio may be caused byDinosaur extinctionIs an important factor.Researchers speculate that the Y chromosome in mammalian males may have evolved mainly to prevent the extinction of species related to climate change.This mechanism of determining gender through heredity can guarantee the balance of gender ratio in offspring.They believe that the warming trend that the world is experiencing may pose a threat to the survival of some existing species that depend on environmental temperature to determine the sex of their offspring.
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Maintain biodiversity
"To keep the biodiversity of the earthEquilibrium stateThe task of adapting to human development is very arduous. Human beings themselves face a very important problem, which is to control the growth of their own population, and at the same time carry out effective, orderly and reasonableProduction mode。”Feng WeiminHe said that if we want to control the rate of species extinction to a certain extent, we must fully realize that although the past mode of production can improveproduction efficiencyHowever, it will cause serious consequences for the sustainable development of human beings.
"Our earth is full of birds singing and flowers fragrance, which is totally different from the past environment. Life is constantly transforming the earth's surface in the process of evolution,Earth environmentThe diversity presented is the result of continuous evolution after countless disasters. "In Feng Weimin's view, not only scientists, but also all people should understand the history of the earth's environmental evolution and the development process of biodiversity, from which we can get useful enlightenment.
Changing the mode of production may be the most important way to save the earth. Building a win-win mode of production for resource development and economic development is the top priority.In this historical process, will we find new ideas, production methods and economic operation concepts?
In the 20th century, China announced the extinction of ten kinds of animals, some of which will soon reach the deadline of 50 years
Xinjiang tiger(Extincted in 1916) OriginLop NurandTarim River Downstream, seen by Si Wen in 1916Lop Nur、Korla。Sven, a Swedish explorer, in his book The Exploration of Lop Nur, described the scene where the local people described the tiger's remains being swallowed by ants.
equus przewalskii (Extincted in the 1960s) Proctor's Mustang, also known asEquus przewalskii 。In 1881, Przewalski of Russia was discovered in Xinjiang and named it Przewalski Mustang.In 1890, a German captured 52 wild horses from China, and after long-distance trafficking to Hamburg, there were only 28, of which 8 bred.However, the last observation of the real wild horse was recorded in the 1960s, and there has been no trace since then.
High nosed antelope(Extinction in 1960s) Before 1960s, in XinjiangJunggar Basin、Beita MountainAnd other regions have discontinuous distribution, and they have not been found since then.
Taiwan clouded leopard(Extincted in 1972) Taiwan clouded leopard, also known as tortoise leopard.In the 1960s, there were records of hunting. Due to deforestation, the demand for fur and leopard bones declined sharply.Since 1972, there has been no leopard in Baodao.
Zhili Macaque(Extincted in the 1980s) Zhili Macaca was once the northernmost primate in China, HebeiWuling MountainIt was established as the northern limit of macaque distributionNational Nature Reserve。In the 20th century, people poured into Wuling Mountain area to cut down, and Zhili macaques became extinct in Wuling Mountain.
White headed stork(The extinction date is unknown) The white headed stork is a large wading bird, which lives in coastal and inland marshes and flood areas in clusters.There have been no wild reports since the 1950s, so it is concluded that China may become extinct.
Dolphin deer(Extincted in the 1970s) Dolphin deer was only found at the border of Gengma and Ximeng County in Yunnan Province in China.Scientists only found a few in the 1960s when they investigated, but they disappeared when they did the investigation again in the 1980s.
Small toothed civet(Extincted in the 1980s) Small toothed civet, only distributed in southern Yunnan in ChinaXishuangbannaMenglaHemengyang.In addition to two specimens obtained in Mengla in the 1970s and three skins acquired in Jinghong and Mengyang, it has disappeared since the 1980s and is estimated to be extinct.
Sickle winged chicken(declared extinct in 2000) Sickle winged chicken is distributed inXiaoxing'an MountainsAnd the lower reaches of Heilongjiang, which can be seen abroadSiberia。In 1986 and 1987, there was no trace.In 2000, Xinhua News Agency announced that after five years of investigation by Heilongjiang Animal Institute, no sickle winged chicken was found, and the local people had not seen it for decades.
Crested duck(Extincted in the middle of the 20th century) Guanma Duck, also known as Fengtou Duck, is native to Northeast China, Japan, Korea and Russia.It was discovered in 1877, 1913 and 1916 respectively.Until May 16, 1964VladivostokOne male, two females and three females appeared, but then disappeared mysteriously.It is estimated that the crested duck was extinct in the middle of the 20th century.
be on the verge of
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worldwide
one
It is also called Baiji and Baiji dolphin, belonging to the beak dolphin family, whose scientific name is Lipotesvexillifer Miller, and belongs to Cetacea and Baiji family.The identification feature is: the snout is long and narrow, about 300 mm long.The forehead is round and bulging.The dorsal fin is triangular, located at 3/5 of the body, and has a low skin ridge connected with the caudal fin.There is a breathing hole on the left side of the head that can be opened and closed freely.The caudal fin is horizontal and concave to the edge in crescent shape.The population of baiji is very small, and it is a rare aquatic animal unique to China, which needs to be protected urgently.Produced inYangtze RiverThe middle and lower reaches of the main stream of Hubei, Anhui and Jiangsu.They have lived in the Yangtze River for about 25 million years“living fossil”The laudatory name of.Due to the extremely small number, it is listed as a first-class protected wild animal in China.
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The Sumatran tigerThere are only 20 in the wild.With the 1940sBalinese tigerAnd the 1970sLi HaihuIt is predicted that this species will also disappear from the earth in the near future.
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The Garamba National Park in Congo has less than 25Sumatran rhinocerous , the northern white rhinoceros will probably disappear completely on the earth.Northern white rhinoceros andSouthern AfricaThe white rhinoceros ofgeneThere are great differences between themUgandaMassive reproduction, but it gradually disappeared due to the lack of local protection.In the Guaramba National Park, the number of them reached 35 in the late 1980s and 30 in April 2003, after which 6 were killed, 4 were newly born, and last month, another 2 were killed. At the same time, nearly 1000 elephants were killed.
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Orinoco CrocodileThe largest carnivore in South America is also one of the 12 most endangered species on the earth.
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Monk seal(monachus monachus ormonkseal) According to expert estimates, there are only 500 in the world, living inmediterranean sea, exposed to sea water and beachesecological environmentDue to the bad influence, they were killed by a large number of fishermen.
Miniature pig(pigmyhog, scientific name Sussalvanius) The smallest pig in the world, a kind of wild boar, mainly lives in northeast India.60 cm long, 25 cm high, less than 10 kg for adult pigs.Once inthe himalayasThere are a large number of them in the region. Only Manas National Park in Assan, India, has a few.Its gene is not very different from that of domestic pigs.
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Spikes parrot: In the wild, although the Spikes parrot is not completely extinct, it is no less.In 1990, the ornithologists who searched for this bird only found one surviving male bird, living in the far northeast of Brazil.About 31 birds captured by people are the hope that this bird can survive.
"It is a very difficult task to keep the biodiversity of the earth in a balanced state and adapt to human development. Humans themselves face a very important problem, that is, to control the growth of their own population, and at the same time to carry out an effective, orderly and reasonable production mode." Feng Weimin said that if we want to control the rate of species extinction to a certain extent,We must be fully aware that although the past mode of production can improve production efficiency, it will cause serious consequences for human sustainable development.
"Our earth is full of birds singing and flowers fragrance, which is totally different from the past environment. Life is constantly transforming the earth's surface in the process of evolution,Earth environmentThe diversity presented is the result of continuous evolution after countless disasters. "In Feng Weimin's view, not only scientists, but also all people should understand the history of the earth's environmental evolution and the development process of biodiversity, from which we can get useful enlightenment.
Changing the mode of production may be the most important way to save the earth. Building a win-win mode of production for resource development and economic development is the top priority.In this historical process, will we find new ideas, production methods and economic operation concepts?
