两种托福阅读文章的段间关系讲解

　　托福阅读需要把握段落关系及篇章结构，而把握段与段之间的关系对于理解托福阅读文章十分重要，在比对段落关系时，和比较句子关系类似，要从段落最主要的意思方面来判断。为了通俗易懂，段间关系可分为总分关系(句子之间称为概述与详述或抽象与具体关系)和并列关系。下面小编就分别从这两种关系出发，给大家详细分析托福阅读文章的段间关系。

　　托福阅读文章的段间关系：总分关系

　　上下两段意思方面相同，相比之下，上一个段落主要内容比下一个段落更具有概括性。

　　Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans. In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale. The fossil was officially named Pakicetus in honor of the country where the discovery was made. Pakicetus was found embedded in rocks formed from river deposits that were 52 million years old. The river that formed these deposits was actually not far from an ancient ocean known as the Tethys Sea. The fossil consists of a complete skull of an archaeocyte, an extinct group of an-cestors of modern cetaceans. Although limited to a skull, the Pakicetus fossil provides precious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack the enlarged space that is filled with fat or oil and used for receiving underwater sound in modern whales. Pakicetus probably detected sound through the ear opening as in land mammals. The skull also lacks a blowhole, another cetacean adaptation for diving. Other features, however, show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans. It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean. It probably bred and gave birth on land.

　　解析：

　　注意：以下分析仅从段落层面角度来看，后文将置于篇章层面来看会出现变化。

　　段1中

　　首句最具有概述性，并提出：许多令人兴奋的发现允许科学家重建最可能的鲸的起源。 其他句子为对P化石发现的背景介绍。

　　段2中

　　第二句为为本段最概述性内容，表明P化石给鲸鱼起源提供许多宝贵细节。 其他句子相对第二句均为细节性内容。

　　段1与段2比较，段1更具有概括性。因此两端中TS在段1中，段2第二句为概述性细节MaD，其余句子均为详述性细节(未进一步分层次)。

　　托福阅读文章的段间关系：并列关系

　　上下两段意思方面不同。

　　Another major discovery was made in Egypt in 1989. Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert. This whale lived around 40 million years ago, 12 million years after Pakicetus. Many incomplete skeletons were found but they included, for the first time in an archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land. Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs. An even more exciting find was reported in 1994, also from Pakistan. The now extinct whale Ambulocetus natans ("the walking whale that swam") lived in the Tethys Sea 49 million years ago. It lived around 3 million years after Pakicetus but 9 million before Basilosaurus. The fossil luckily includes a good portion of the hind legs. The legs were strong and ended in long feet very much like those of a modern pinniped. The legs were certainly functional both on land and at sea. The whale retained a tail and lacked a fluke, the major means of locomotion in modern cetaceans.The structure of the backbone shows, however, that Ambulocetus swam like modern whales by moving the rear portion of its body up and down, even though a fluke was missing. The large hind legs were used for propulsion in water. On land, where it probably bred and gave birth, Ambulocetus may have moved around very much like a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea.

　　解析：

　　段1中

　　末句最具概述性，并提出：B毫无疑问是完全海生的鲸并有不起作用或退化了的后腿。

　　段2中

　　末句最具概述性，并提出：A毫无疑问是连接陆地和海洋生命的鲸。

　　段1与段2意思方面不同，为并列关系。