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Environmental scientists observe that it is of great significance to protect wildlife and wild places ff human beings want to su
Environmental scientists observe that it is of great significance to protect wildlife and wild places ff human beings want to su
admin
2010-06-18
19
问题
Environmental scientists observe that it is of
great significance to protect wildlife and wild places
ff human beings want to survive. We must under-
stand the important links between ourselves and the
wild plants and animals in our environmental
【1】______ system. 【1】______
Diseases and insects can develop to destroy
some kinds of plants and animals. So a supply of
different kinds of plants is needed. The new species
can be found in the wild or be obtained by Scientists
who mix【2】______material from different species.【2】______
For example, 100 years ago, scientists grew
the European vine on【3】______from the American 【3】______
vine. In this way the European【4】______ 【4】______
industry was saved.
In recent years, scientists have expressed concern
that coffee trees in Brazil and soybean plants in
America come from limited wild species. They are
easily attacked by insects, diseases, or severe
weather conditions.
Scientists are also concerned about the loss of
traditional farm animals. For example, almost 115
out of the original【5】______kinds of cattle in 【5】______
Europe and the Mediterranean area are endangered.
Traditional farm animals can be very valuable,
e.g. a rare European sheep, Cornish hen etc. Some
scientists say this kind of hen can be mated with
other species of chickens to introduce a
【6】______ bird for food. 【6】______
Wild plants and animals are important to medicine,
too. A study shows that about 40 percent of
the medicines in U.S. contain drugs from plants,
animals, etc. For example, cancer scientists are using
a plant to fight a cancer of【7】______ 【7】______
Wild plants and animals are disappearing at an
increasing speed, yet there are still success stories.
For example, the number of elephants killed
【8】______in Africa has decreased dramatically. 【8】______
In another case, 400 gorillas survive in a
【9】______area in Africa because Rwanda developed【9】______
an important business that relies on protecting
the gorillas.
Another successful program takes the endangered
animals from their natural homes to protected
zones where they can【10】______safely. 【10】______
【2】
Environmental scientists say protecting wildlife and wild places is extremely important if the world is to continue to support human life. These experts say we must understand the important links between ourselves and the wild plants and animals in our environmental support system. They note that no one knows for sure which of these plants and animals may be useful to us in the future.
Through the years, diseases and insects develop that can destroy some kinds of plants and animals. Farmers then need a new supply of different kinds of plants to grow and animals to raise for food and work. These new species are found in the wild. Or scientists mix genetic material from many different species to develop new ones. For example, 100 years ago, an insect killed off European grape plants. But scientists discovered that American grape plants were not affected by the insect. So the scientists grew the European wine on roots from the American vine. The grapes produced in this way saved the European wine industry.
In recent years, scientists have expressed concern that almost every coffee tree in Brazil comes from one kind of plant. And all soybean plants in the United States come from six kinds of soybeans found in one place in Asia. The scientists fear that a change in weather conditions or an attack by insects or disease, could destroy Brazil’s coffee trees and America’s soybean plants. This would not happen if we grew different kinds of coffee trees and soybean plants. They would not all be affected by the same weather, insects or disease.
Scientists also are concerned about the loss of many species of traditional farm animals. For example, almost 115 of the original 145 kinds of cattle in Europe and the Mediterranean area are in danger of dying out.
Traditional kinds of farm animals can be very valuable. A rare European sheep, for example, has been used to produce a kind of sheep that can survive where the weather is very hot. And it still produces good wool. Other scientists have worked with the Cornish hen. They say it can be mated with other species of chickens to produce a fast-growing bird for food.
Wild plants and animals also are important to modern medicine. One study say that 40 percent of the medicines used each year in the United States contain drugs that come from plants, animals or small living organisms. For example, cancer scientists are using a periwinkle plant from Madagascar. The plant contains a chemical that may be used to fight leukemia, a cancer of the blood. Other chemicals from plants provide medicines that fight diseases such as malaria. Others improve heart and lung action, or kill pain, or stop dangerous growths. Yet scientists have been able to study only a small number of the world’s plants to find their value as medicines.
While plant and animal species are disappearing at a rapidly increasing rate throughout the world, scientists note some success stories. For example, the number of elephants killed illegally in Africa has fallen sharply. Eighty nine thousand were killed in 1983. Forty six thousand were killed one year later.
Successful efforts also have been made in protecting Africa’s endangered mountain gorillas. Almost 400 of the gorillas survive in a volcano area on the border of Rwanda, Uganda and Zaire. The mountain gorilla population has remained about the same for 15 years. This happened, in part, because Rwanda developed an important business that depends on protecting the gorillas. Visitors there can pay to get close to watch the gorillas in the animals’ traditional home area.
Another successful program takes endangered animals out of their natural homes. The animals are put into zoos or their protected areas where they can reproduce in safety. The goal of many of these programs is to produce enough animals to put back into the wild.
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答案
genetic
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