50 years later more than one hundred of thousands of terrestrial biology from the Earth. Because of the impact of human activities, than the natural extinction of species extinction rates 1,000 times faster, on average there is one species extinction per hour.
Biological evolution in a long, long term stability of the dramatic changes of always short term alternating with extinction also occurs at different scales. In a stable period, the average new rate far greater than the average extinction rate, the total average extinction rate remains at a low level, such a low level of extinction is called background extinction; Correspondingly, in the upheaval of many biological categories extinction in the short term, a sudden interruption of the process of biological evolution, so that a sudden increase in extinction rate, while the new rate is down so low, this is called mass extinction mass extinction or major extinction.
According to statistics, since the Cambrian has been significant extinction event 15 times. Of which there are 5 major mass extinction. Scientists have been studying the causes and patterns of extinction and made a variety of explanations, such as meteorite impacts, cosmic rays and strong, volcanic eruptions, climate change, atmospheric composition changes, changes in ocean salinity, geomagnetic changes. The previous mass extinctions are a natural disaster, but the 6th is artificial. We are going through the history of extinction of life on Earth other than the extinction of the incident even worse. Some experts say.
The number of species around the world do? Some said that 1.5 million kinds, and some say 1.7 million kinds of even two million kinds. These figures refer to the known species, there are many species we have not found the actual figure will be far greater than now.
The World Conservation Union (IUCN) released every few years the situation of a global species, Red Book, the most recent Red List of species have 15,589 species are threatened with extinction. Including 12 of bird species, 23 of mammals, 32 of amphibians, 25 of the gymnosperms, cycads 52 , 42 of the turtles, sharks and rays of 18 , 27 of East Africa freshwater fish.
5 major threat to biodiversity
Why so serious global environmental situation? Experts concluded the following 5 main reasons: First, habitat loss or fragmentation; second, invasion of exotic species; Third, environmental pollution; the fourth, a population explosion; Fifth, over exploitation.
To understand the danger of species extinction has much, we must first understand its genetic diversity. Such as two grass looked like, not tell to the naked eye, but they are no doubt on the genetic basis of distinction, and this is the uniqueness of the individual, and now we can high resolution molecular markers to distinguish individuals. Yuan Longping you are familiar with the contribution of rice production on the increase, but if you do not do very hard to find wild rice hybrid, he can not have the present results; dwarfing gene on the promotion of China s grain output, also played a very crucial effect.
In this sense, a gene may change a country s economic situation. Because in an ecosystem, each species has its own special features. Extinction of a species each, there are several dozens of species of living affected.
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