1、Passage oneHumans have used the windmill to harness wind power for thousands of years. However, it was not until the 19th century that windmills possessed the features that made them efficient in the same way as modern wind turbine blades. The windmill was refined when its heavy, inefficient wooden
2、blades were replaced with lighter, faster steel blades around 1870. Over the next century, more than six million small windmills were built in the western US, where they pumped ground water for livestock and provided the domestic water supply for families living on remote ranches. The first large wi
3、ndmill to produce electricity was a multi-blade design with a 12-kilowatt capability, built in 1888. Today, wind power is a promising, clean, safe, and environmentally friendly energy resource that can serve as an alternative to electricity generated by fossil fuels such as coal, oil, and natural ga
4、s. In 1999, wind-generated electricity exceeded 10,000 megawatts globally, which amounts to approximately 16 million kilowatt-hours of electricity. This is more than enough to serve five medium-sized cities with a population of 350,000 each.Wind-generated electricity is projected to be one of the de
5、veloping worlds most important sources of energy, and it also has potential for industrialized nations. Wind power could provide 20 percent of the electricity in the US, with turbines installed on less than one percent of the nations land area. Within that area, less than 5 percent of the land would
6、 be occupied by wind equipment; the remaining 95 percent could continue to be used for farming or ranching. Passage twoProfessors are normally found in university classrooms, offices, and libraries doing research and lecturing to their students. More and more, however, they also appear as guests on
7、television news programs, giving expert commentary on the latest events in the world. These television appearances are of great benefit to the professors themselves as well as to their universities and the general public.Professors benefit from appearing on television because by doing so they acquir
8、e reputations as authorities in their academic fields among a much wider audience than they have on campus. If a professor publishes views in an academic journal, only other scholars will learn about and appreciate those views. But when a professor appears on TV, thousands of people outside the narr
9、ow academic community become aware of the professors ideas. So when professors share their ideas with a television audience, the professors importance as scholars is enhanced.Universities also benefit from such appearances. The universities receive positive publicity when their professors appear on
10、TV. When people see a knowledgeable faculty member of a university on television, they think more highly of that university. That then leads to an improved reputation for the university. And that improved reputation in turn leads to more donations for the university and more applications from potent
11、ial students.Finally, the public gains from professors appearing on television. Most television viewers normally have no contact with university professors. When professors appear on television, viewers have a chance to learn from experts and to be exposed to views they might otherwise never hear ab
12、out. Television is generally a medium for commentary that tends to be superficial, not deep or thoughtful. From professors on television, by contrast, viewers get a taste of real expertise and insight.Passage threeAltruism is a type of behavior in which an animal sacrifices its own interest for that
13、of another animal or group of animals. Altruism is the opposite of selfishness; individualsperforming altruistic acts gain nothing for themselves.Examples of altruism abound, both among humans and among other mammals.Unselfish acts among humans range from the sharing of food with strangersto the don
14、ation of body organs to family members, and even to strangers. Suchacts are altruistic in that they benefit another, yet provide little reward to the oneperforming the act.In fact, many species of animals appear willing to sacrifice food, or even theirlife, to assist other members of their group. Th
15、e meerkat, which is a mammal thatdwells in burrows in grassland areas of Africa, is often cited as an example. Ingroups of meerkats, an individual acts as a sentinel, standing guard and looking outfor predators while the others hunt for food or eat food they have obtained. If thesentinel meerkat see
16、s a predator such as a hawk approaching the group, it gives analarm cry alerting the other meerkats to run and seek shelter. By standing guard,the sentinel meerkat gains nothingit goes without food while the others eat, andit places itself in grave danger. After it issues an alarm, it has to flee al
17、one, whichmight make it more at risk to a predator, since animals in groups are often able towork together to fend off a predator. So the altruistic sentinel behavior helps ensurethe survival of other members of the meerkats groupPassage fourIn the area today covered be several states in the America
18、n Southwest, the Anasazi Indians, who are sometimes referred to as Pueblo Indians, once lived. The Anasazi had a history that went back into prehistoric times. They even experienced a several-hundred- year golden age that ended around 1150. However, the Anasazi suddenly vanished only a couple of cen
19、turies later. Many anthropologies attribute their disappearance to war.Archaeologists have combed through the ruins of past Anasazi settlements. One feature they have noted is that there are a large number of places which were burned. Even some of the Anasazis ritual sites were burned. This strongly
20、 suggests the reason for the burnings was invasions by warring tribes. Many American Indian tribes would burn the settlements of the tribes they has defeated in battle. The fact that Anasazi sites were burned shows they too must have been conquered.At these same sites, archaeologists have also unear
21、thed a large number of personal articles That once belonged to individual Anasazi. Many of these items, including pottery, jewelry, and other personal effects, would have been valuable to their owners. In most cases, their owners would not have left them. However, many believe that because of the su
22、dden onset of war, their owners were either slain or had no time to gather their belongings as they fled from approaching enemies.There is also the geographical aspect of the Anasazi. Their settlements, which were mostly in modern-day Arizona and New Mexico, were located in places with abundant sour
23、ces of water, a unique feature for the American Southwest. It would Only be natural that other tribes, coveting the rich land, would make war upon the Anasazi and attempt to drive them out, as they, apparently successfully, did.Passage fiveThe dodo was a large, flightless bird nativeto the island of
24、 Mauritius in the Indian Ocean. Mauritius was colonized by Dutch settlers in the late 16th century, and ,fewer than 100 years later, the last dodo disappeared. There is much speculation as to why the dodo disappeared, but experts have arrowed the reasons down to the actions of humans.There were no h
25、umans on Mauritius prior to the Dutchs arrival, so the dodos had no fear of humans and thus were easily hunted. The Dutch also brought other animals, such as cats, dogs , pigs and various farm animals, and there were many instances where these animals hunted dodos or destroyed their eggs and nests.
26、The dodo, being flightless, built its nests on the ground in forested areas and laid its eggs in these nests. The eggs and young dodos therefore had no protection against predators.When the Dutch colonized Mauritius, they began rapidly altering the land for farming. They cleared forests, and this ac
27、tion destroyed the dodos natural habitats. The dodos soon had fewer places to make their nests and lay their eggs. Also, since the dodos fed on the tropical fruits native to the island, when the Dutch chopped down the trees, a large part of the dodos food supply was destroyed.Some also speculate tha
28、t outsiders introduced a disease which proceeded to wipe out the dodos. Some diseases may pass from human to animals or, more commonly, from animal to animal. This would account for the virtually overnight disappearance of the dodos. The introduction to a new species often wreaks havoc on the natives. For example, when the European settlers arrived in America, many Native Americans died due to a lack of immunity to new diseases. The same could easily have happened to the dodo.
