What is the relationship between organisms in the African savannah ecosystem?

1) The atmospheric environment is deteriorating. The main manifestations are: the increase and intensification of climate disasters, global warming, melting glaciers, rising sea levels, and the threat of coastal lowlands being submerged by seawater; The change of atmospheric composition is not conducive to human beings, carbon dioxide increases, the concentration of ozone layer that relieves ultraviolet radiation decreases, the ozone layer above the earth's poles appears holes and is increasing, and many harmful components are also increasing. According to the report of American Ritchie National Laboratory 1997, since the industrial revolution, the concentration of carbon dioxide in the atmosphere has increased by 30%, methane has doubled, and nitrogen oxides have increased by 15%. Carbon dioxide, methane and nitrogen oxides are all gases that can produce greenhouse effect, and the increase of their concentrations leads to the increase of temperature.

These changes in the atmosphere are caused by nature itself. Volcanic eruptions and forest fires will release pollutants into the atmosphere. However, the use of fossil fuels such as coal and oil releases harmful gases and dust such as carbon dioxide, methane, nitrogen oxides and sulfur dioxide, which makes air pollution more serious. Coal burning produces the most pollutants. The resulting poisonous fog and acid rain are outstanding manifestations of air pollution. "Killing Smoke" first appeared in Belgium in 1930, and enveloped London four times from 1948 to 1962. The concentration of sulfur dioxide and dust in smoke greatly exceeded human tolerance, resulting in more than 6,000 deaths. Although this kind of record is rare, polluted air generally permeates the space of many industrial and mining areas and cities.

Ordinary rainwater often contains trace amounts of carbonic acid. Sulfur dioxide, nitrogen oxides and other components are added to the polluted atmosphere, which makes the rainwater more acidic. At present, people define rain with pH below 5.6 as acid rain. It looks like ordinary rain, but the acidic substances it contains enter the soil and water on the surface, and the organisms that depend on these water and soil are adversely affected, especially the destruction of forests. 1939 The pH value recorded as acid rain for the first time is 5.9 (pure water pH value is 7). In 1950s, the pH value of acid rain dropped to 3-5, and the lowest was 2. 1, which was almost even stronger than vinegar. It shows that with the development of industry, the degree of air pollution is becoming more and more serious. Because the atmosphere containing pollutants is mobile and can cross the ocean, the acidic components emitted by Japan can form acid rain in the United States, and it is not surprising that acid rain in Canada originated in the United States. Scientists have measured that two-thirds of the sulfur dioxide gas gathered over Sweden and Norway comes from industrial areas in Britain and Germany.

With the rapid development of China's economy, the area covered by acid rain has also expanded rapidly, with 1999 becoming the third largest acid rain area in the world, next to Europe and North America. China still uses coal as its main fuel, which is one of the reasons for serious air pollution.

The damage caused by air pollution is extremely extensive. Many times, it does not appear in the form of poisonous fog and acid rain, but all kinds of creatures are often affected by it, especially the damage to forests and crops. Frequent breathing of polluted air is also a threat to human health, especially respiratory diseases. Living in a polluted atmospheric environment for a long time is just like chronic poisoning.

Ozone in the atmosphere can't make ends meet, and its concentration decreases. Scientists first discovered in 1985 that in September and October of 1984, the ozone concentration in the ozone layer over Antarctica was 40% lower than that in the mid-1970s, which could not completely block too much ultraviolet rays, resulting in a "hole" in this special life protection circle, threatening the survival of Antarctic marine phytoplankton. According to the report of the World Meteorological Organization, it was found in 1994 that the ozone content in the stratosphere over the Arctic region also decreased, and in some months it decreased by 25-30% compared with that in the 1960s. However, the ozone hole over Antarctica is still expanding, with the largest area reaching 25 million Km2 in1September 1998. *

Why is there a hole in the ozone layer? Many scientists believe that it is the result of using freon as refrigerant. Freon consists of carbon, chlorine and fluorine. After chloride ions are released into the atmosphere, ozone molecules can be destroyed repeatedly and remain unchanged. Therefore, even if the amount is small, ozone molecules can be reduced to form "holes". Recently, scientists in China suggested that it is not enough to rely solely on the action of Freon. The particle flow of solar wind is concentrated to the geomagnetic pole under the action of geomagnetic field, where ozone molecules are destroyed, which is the main reason. (Yang Xuexiang, 1999) In any case, artificially discharging chloride ions into the atmosphere is a harmful behavior.

In the atmosphere, substances are loosely distributed and move at a high speed, and small external disturbances may also upset the original balance, so the impact of human activities on the atmospheric environment cannot be underestimated.

There are about 100 kinds of pollutants that have been harmful or noticed in the atmosphere, among which hydrocarbons, carbon monoxide, nitrogen oxides, sulfur oxides, hydrogen sulfide, fluoride, photochemical oxidants and particulate matter are the main threats to the human environment.

(2) The hydrosphere is seriously polluted

The biggest problem of hydrosphere is the shortage of fresh water resources and uneven geographical distribution, which has become an obstacle to the sustainable development of some countries and regions (see chapter 12), and the pollution of hydrosphere has threatened the survival of mankind. 199 On the occasion of World Water Day, UN experts announced that1400 million people still drink unsafe water in the world today, and more than 5 million people die of diseases every year. In China, after the great development of economic construction, most rivers have been polluted to varying degrees. In other countries, the more developed the industry, the more serious the water pollution. The polluted atmosphere can be diluted rapidly after flowing and diffusing; Although polluted water can also flow, it often exists in relatively stable water bodies. It has had a long-term and far-reaching impact on people and creatures living on water.

There are natural factors that cause water and water pollution. However, with the development of industry and the use of fertilizers, pesticides and a large number of chemicals in life, the pollution of hydrosphere has developed to the present harmful level.

Wastewater discharged from industrial production, domestic sewage and agricultural backwater often become the main pollution sources today. There are many kinds of pollutants in water, including metals, nonmetallic substances and organic substances, many of which are harmful to human body and even highly toxic. Although it can be purified by manual treatment, most of it is only slightly treated, or even directly discharged into natural water without treatment.

In 1950s and 1960s, Minamata disease occurred in both Minamata City and Niigata Prefecture, Japan. The reason is that the mercury in the wastewater discharged by the factory is gradually enriched through the biological food chain (diatom-flying squid-grouper-eel), so that the mercury content in eel reaches 65,438+00-20 mg per liter (up to 50-20mg). After local residents preyed on eels, mercury accumulated in the human body, causing serious damage to the central nervous system. Water pollution is very harmful to human body and aquatic organisms, especially the pollution of toxic and harmful substances will cause chronic poisoning, acute poisoning and even death. Water polluted by germs is the source of infectious diseases. Water pollution is very harmful to human body and aquatic organisms, especially the pollution of toxic and harmful substances will cause chronic poisoning, acute poisoning and even death. Water polluted by germs is the source of infectious diseases.

Most rivers eventually flow into the ocean, and harmful and harmless substances are concentrated in the ocean with the rivers; The rupture or sinking of an oil tanker is bringing oil that may seriously pollute the sea into the sea. In some places, people also dump garbage into the sea. The ocean is a cornucopia and self-purification pool of nature, but some people regard it as a sewage pool and a garbage can. Near the developed industrial areas, there are no fishing grounds in the Mediterranean, and many species are extinct here. Due to the expansion of surrounding cities and the rise of industry, this development trend also appears in Bohai Sea in China. 1998 The report of the monitoring department shows that 56% of the Bohai sea area in 1995 is polluted, which is twice as large as that of ten years ago and is still expanding. Rivers, lakes and oceans all have self-purification functions, so the water in nature has always been crystal clear, and now it is polluted and still developing, which is completely the result of human carelessness. The hydrosphere is a system in which pollutants diffuse with the movement of water, so pesticides are also found in the tissues of Antarctic penguins. The red tide (red tide) that affects the vast sea area comes from urban sewage. These sewage are rich in phosphorus, nitrogen and other elements and organic matter needed for biological nutrition. Red tide is a phenomenon that some red or maroon algae get rich nutrition, grow rapidly and increase in number. Because of their excessive reproduction and decay after death, they consume a lot of oxygen, which affects other organisms, especially fish. Biosphere and food chain

Biosphere is a huge and extremely complex ecosystem. It consists of countless ecosystems of different sizes. These ecosystems can be basically divided into three categories: terrestrial ecosystems, freshwater ecosystems and marine ecosystems.

Terrestrial ecosystem refers to the ecological environment that constitutes terrestrial vivid plants, such as the subtropical jungle in Xishuangbanna, China, Asian elephants, South China tigers and clouded leopards in the jungle, together with various birds and other small animals, forming a complete ecosystem. For example, in many grasslands in northern China, there are not only scenes of wind and grass and flocks of cattle and sheep everywhere, but also a paradise for all kinds of wild animals and birds. The snowy plateau and Gobi desert look desolate, but they not only have life, but also have their own ecosystems because of interdependence and environmental impact.

Freshwater ecosystem usually refers to the interdependence between freshwater organisms in rivers, lakes and swamps and the natural environment generated by them. In this ecosystem, the main body is fresh water, and all other aquatic animals and plants are objects. As long as it doesn't destroy the fresh water environment of the subject, the object generally won't have much problem. Then, this ecosystem can basically maintain balance.

Marine ecosystem, as its name implies, refers to the natural environment formed by various animal and plant groups under the main conditions of the ocean. The sea is rough and unruly, but the underwater world photographed by underwater cameras is so quiet, peaceful, warm and wonderful!

The various ecosystems that make up the biosphere have their own characteristics in structure and function, which play a special role and jointly maintain the normal function of the biosphere. This is what we usually call ecological balance.

Food chain refers to the food network relationship formed by mutual restriction and interdependence among organisms. For example, carnivores-herbivores and insects-birds in grassland ecology restrict each other and coexist and prosper together. The relationship between them is unity of opposites and natural harmony. On the African savannah, carnivores such as lions, cheetahs and hunting dogs specialize in herbivores, and their killing of wildebeests and even zebras is very brutal. However, this cruel killing is not only necessary for the survival and reproduction of carnivores, but also an essential factor for maintaining the lush grassland plants and ecological balance. Without the control of carnivores on herbivores, herbivores will develop rapidly. When the number of herbivores reaches a certain level, the grassland will be overwhelmed and degraded, and the herbivores will lose the conditions for survival and development. Killing herbivores by carnivores can not only control the number of herbivores, but also improve the quality of herbivores in a sense. After a long-term field investigation, biologists have proved that carnivores often choose sickly herbivores in the hunting process, which is undoubtedly conducive to the survival of the fittest. From this point of view, the brutal killing of herbivores by carnivores is natural and reasonable.

Carnivores feed on herbivores, which protect the grassland while controlling the number of herbivores. All kinds of birds prey on insects, just like carnivores, and also play a role in protecting grasslands. The excrement of birds and animals has become a good fertilizer to promote the growth of various plants. This food chain with plants as the main body and herbivores, carnivores and insects-birds as the objects plays an important role in maintaining the ecological balance of grassland. Hulunbeier grassland is one of the largest grasslands in northern China, and the largest animal husbandry base in China, with abundant pasture and flocks of cattle and sheep. However, in history, because of the wild wolves here, it poses a serious threat to the development of animal husbandry. In order to protect human and animal safety, local herders once organized large-scale wild wolf hunting activities, and the number of wild wolves decreased sharply. The remaining wolves no longer dared to take the grassland as their home and feed on cattle and sheep, and all moved to the deep mountains and forests. The wolves disappeared and animal husbandry developed unprecedentedly. At the same time, the number of cattle and sheep has been increasing, and rabbits have also developed at an alarming rate. Rabbits and cattle and sheep compete for pasture, and the grassland is unbearable, which leads to the rapid degradation of grassland and the danger of desertification.

Facts make people realize that once there is a problem in any link of the food chain, disaster will soon come. Wolves will poach cattle and sheep when they are hungry, but under normal circumstances wolves feed on rabbits. From this point of view, it is wild wolves that control the reproduction and development of rabbits, avoid the phenomenon that rabbits compete with cattle and sheep for food, and ensure the normal ecological environment of grassland. After the herdsmen realized this natural law, they were much more tolerant of wild wolves. They never talked about the color change of wolves again, and they beat them whenever they saw it.

Man is not only a part of the biosphere, but also plays a leading role in various ecosystems of the biosphere. People can protect various ecosystems and promote ecological balance through their own efforts; People can also plunder resources and destroy the ecological balance for their own vital interests. We must be soberly aware that human beings cannot exist supernatural, and protecting ecological balance is also protecting human beings themselves. Once the ecological balance is destroyed, the whole biosphere is threatened, and human beings themselves are doomed.