【正文】 are in many respects like traditional printed encyclopedias collections of articles on various subjects. What is specific to these online encyclopedias, however, is that any Inter user can contribute a new article or make an editorial change in an existing one. As a result, the encyclopedia is authored by the whole munity of Inter users. The idea might sound attractive, but the munal online encyclopedias have several important problems that make them much less valuable than traditional, printed encyclopedias. First, contributors to a munal online encyclopedia often lack academic credentials, thereby making their contributions partially informed at best and downright inaccurate in many cases. Traditional encyclopedias are written by trained experts who adhere to standards of academic rigor that nonspecialists cannot really achieve. Second, even if the original entry in the online encyclopedia is correct, the munal nature of these online encyclopedias gives unscrupulous users and vandals or hackers the opportunity to fabricate, delete, and corrupt information in the encyclopedia. Once changes have been made to the original text, an unsuspecting user cannot tell the entry has been tampered with. None of this is possible with a traditional encyclopedia. Third, the munal encyclopedias focus too frequently, and in too great a depth, on trivial and popular topics, which creates a false impression of what is important and what is not. A child doing research for a school project may discover that a major historical event receives as much attention in an online encyclopedia as, say, a single longrunning television program. The traditional encyclopedia provides a considered view of what topics to include or exclude and contains a sense of proportion that online democratic munal encyclopedias do not. Listening Professor: The munal online encyclopedia wil! probably never be perfect, but that39。t there more remains of big containers? Third, the idea that the great houses were ceremonial centers isn39。 unsupported by evidence. It may sound plausible that large empty rooms were used for storage, but excavations of the great houses have not uncovered many traces of maize or maize containers. If the great houses were used for storage, why isn39。t have been residential. Second, the idea that the great houses were used to store grain m163。t rapidly growing. These growth rings are evidence that dinosaurs stopped growing or grew more slowly during cooler periods. This pattern of periodic growth, you know, rapid growth followed by no growth or slow growth, and then rapid growth again, is characteristic of animals that are not endotherms. Animals that maintain a constant body temperature yearround as true endotherms do grow rapidly even when the environment bees cool. TPO5 Reading As early as the twelfth century ., the settlements of Chaco Canyon in New Mexico in the American Southwest were notable for their great houses, massive stone buildings that contain hundreds of rooms and often stand three or four stories high. Archaeologists have been trying to determine how the buildings were used. While there is still no universally agreed upon explanation, there are three peting theories. One theory holds that the Chaco structures were purely residential, with each housing hundreds of people. Supporters of this theory have interpreted Chaco great houses as earlier versions of the architecture seen in more recent Southwest societies. In particular, the Chaco houses appear strikingly similar to the large, wellknown apartment buildings at Taos, New Mexico, in which many people have been living for centuries. A second theory contends that the Chaco structures were used to store food supplies. One of the main crops of the Chaco people was grain maize, which could be stored for long periods of time without spoiling and could serve as a longlasting supply of food. The supplies of maize had to be stored somewhere, and the size of the great houses would make them very suitable for the purpose. A third theory proposes that houses were used as ceremonial centers. Close to one house, called Pueblo Alto, archaeologists identified an enormous mound formed by a pile of old material. Excavations of the mound revealed deposits containing a surprisingly large number of broken pots. This finding has been interpreted as evidence that people gathered at Pueblo Alto for special ceremonies. At the ceremonies, they ate festive meals and then discarded the pots in which the meals had been prepared or served. Such ceremonies have been documented for other Native American cultures. Listening Professor: Unfortunately none of the arguments about what the Chaco great houses were used for is c First, sure, from the outside, the great houses look like later and native American apartment ^ ut the inside of the great houses casts serious doubt on the idea that many people lived there. I39。t need the idea of endothermy and running to explain why dinosaurs evolved to have their legs under their bodies. Ok, so how about bone structure? Many dinosaur bones do have Haversian canals, that39。t prove the dinosaurs were endotherms. Well, what about the fact that dinosaurs have their legs placed under their bodies, not out to the side like crocodiles. That doesn39。s side, as they are for crocodiles and many lizards. The legs of all modern endotherms are underneath the body, and so were the legs of dinosaurs. This strongly suggests that dinosaurs were endotherms. Haversian canals There is also a connection between endothermy and bone structure. The bones of endotherms usually include structures called Haversian canals. These canals house nerves and blood vessels that allow the living animal to grow quickly, and rapid body growth is in fact a characteristic of e