题目内容
The history of global diversity can be summarized as follows: after the initial flowering of multi-cellular animals, there was a swift rise in the number of species in early Paleozoic times (between 600 and 430 million years ago), then plate-alike stagnation for the remaining 200 million years of the Paleozoic era, and finally a slow but steady climb through the Mesozoic and Cenozoic eras to diversity's all-time high. This history suggests that biological diversity was hard won and a long time in coming. Furthermore, this pattern of increase was set back by five massive extinction episodes. The most recent of these, during the Cretaceous period, is by far the most famous, because it ended the age of the dinosaurs, giving hegemony to the mammals, thus ultimately making possible the dominance of the human species over the Earth. But the Cretaceous crisis was minor compared with the Permian extinctions 240 million years ago, during which between 77 and 96 percent of marine animal species perished. It took five million years, well into Mesozoic times, for species diversity to begin a significant recovery.
Within the past 10,000 years biological diversity has entered a wholly new era. Human activity has had a devastating effect on species diversity, and the rate of human-induced extinctions is accelerating. Half of the bird species of Polynesia have been eliminated through hunting and the destruction of native forests. The list of such biogeographic disasters is extensive.
Because every species is unique and irreplaceable, the loss of biodiversity is the most profound process of environmental change. Its consequences are also the least predictable because the value of the Earth's species remains largely unstudied and unappreciated; unlike material and cultural wealth, which we understand because they are the substance of our everyday lives, biological wealth is usually taken for granted. This is a serious strategic error, one that will be increasingly regretted as time passes.
Which one of the following best expresses the main idea of the passage？
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What is true about the Cretaceous crisis according to the author？
Over the past thirty years, the incidence of suicides among college-age individuals has risen 284 percent. This dramatic increase is explained in numerous ways by experts from different domains.
Although there is typically no single reason for a suicide, authorities have compiled several reasons why a college student may attempt it.
First, scholastic anxiety may contribute to a student's dissatisfaction with life. Parental and peer pressure for scholastic achievement may become an unreasonable burden. Since competition for grades and academic achievement is becoming fiercer on today's campuses, the student who is worried or anxious about grades may become extremely distraught and depressed.
Second, students face high unemployment rates. Economic hardship is often a hallmark of suicide.
Third, a stressful social life can make a college student feel rejected, abandoned and dissatisfied. Individuals who have problems adjusting to social life in college are frequently considered likely candidates for attempting suicide since they lack companionship and thus may feel as though no one cares about them.
There is an encouraging note in the bleak picture. A high percent of suicidal individuals — 80% — indicate their intention. An actual suicide such as "You'd better off without me" and "Life has lost all meaning" fall into this category. Another possible indication is the situational hint, such as a person's poor health, economic distress, breakups of relationships, and family problems. A fourth possible indication is the emotional hint, which involves changes in behavior. and levels of energy.
The suicide of at least 5,000 higher education students per year is a devastating loss — to family and friends, to the college, and to the community. Since early detection and treatment of depression are the greatest deterrents to suicide, educators and colleges may be in unique positions to help prevent these losses. Studies report that establishing crisis intervention centers on campuses is highly effective step.
Two major components are necessary before these centers can be completely functional. The first is a twenty-four hour telephone answering service. Personnel answering the phone can be professionals. A second component is the presence of professional counselors. Students who contemplate or attempt suicide need professional guidance.
Typically, campus crisis centers perform. three functions. First, they educate and inform. the community about suicide. If other students and professors are taught to recognize symptoms of a suicidal individual, then early detection and intervention may be possible before an individual even attempts suicide. Second, the centers provide counseling for victims who have attempted suicide. Since statistics show that four of five people who commit suicide tried it at least once before, this intervention is of the outmost importance. The third functions of a crisis intervention center on a campus is to counsel individuals who were friends, roommates, and relatives of the victims.
The college's roll in early detection and intervention for its troubled students may be relatively simple, requiring only minimum facilities and personnel, and institutional awareness and concern.
The article is primarily about
At first, the professor was talking about the problem of education, he suddenly ______ to
The consequences from the loss of biodiversity are difficult to predict because
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