【待插入句子】One example of such tropical abundance is found in Panama, which has 667 species of breeding birds一three times the number found in Alaska.

【待插入段落】 When we look at the way in which biodiversity (biological diversity) is distributed over the land surface of the planet, we find that it is far from even. The tropics contain many more species overall than an equivalent area at the higher latitudes. This seems to be true for many different groups of animals and plants.

Why is it that higher latitudes have lower diversities than the tropics? Perhaps it is simply a matter of land area. The tropics contain a larger surface area of land than higher latitudes—a fact that is not always evident when we examine commonly used projections of Earth’s curved surface, since this tends to exaggerate the areas of land in the higher latitudes—and some biogeographers regard the differences in diversity as a reflection of this effect. But an analysis of the data by biologist Klaus Rohde does not support this explanation. Although area may contribute to biodiversity, it is certainly not the whole story; otherwise, large landmasses would always be richer in species.

1.首先公布答案：1st square;

2.看到待插入句子中有one example…，这是个典型的论点+论据的结构! 给我们的是论据，那么前面一定要出现论点，这样才能和举例子对应起来。 之后，看看举的是什么样的例子——这样的热带多样性被发现在Panama，有667个鸟类物种，是Alaska的三倍。

3.最后让我们来看一下待插入段落的各个句子：

P1:1st:当我们来看生物多样性(biodiversity)在地表分布的方式时，我们会发现这种分布(it)不是(far from)均匀的(even)。2nd:热带(tropics)比同样(equivalent)面积的高纬度(higher latitudes)地区包含了更多地物种。 3rd:这种现象对许多不同种类的动植物都是正确的。

P2: 1st: 为什么高纬度有(比热带)更低的多样性?

2nd: 可能只是陆地面积的缘故。(托福中经典的自问自答!)

3rd:热带(比高纬度区域)包含了更大的地表面积，有些生物地理学家把这种多样性的差异(differnece in diversity)当成是(regard...as)这种结果(this effect, 只带前半句的热带面积更大)的反射——面积的事实(a fact)在我们看地球曲面投影图的时候并不总是明显的，因为投影(this)会夸大(exaggerate)高纬度地区的陆地面积。(这一句也考到了句子简化题，注意”先大后小”的原则，破折号留到后面读)

4th: 但是KR的数据分析并不支持这个解释。

5th:尽管面积可能导致(contribute to…)生物多样性，它当然不是全部的理由(not the whole story);否则(otherwise),大的地表面积就应该总是有更丰富的物种。 (言外之意是 并非如此。——考察常识)

看完之后就很清楚了，第一个段落讲现象，第二个段落讲原因。而待插入的句子说的是现象，所以放在第一段关于生物多样性的论点后面，perfect。

语法积累

far from… 跟上次课讲过的other than…一样，表示否定。

more…than…;lower…than…; larger…than… 识别比较关系。

regard…as… 被认为...

not the whole story 字面理解为“不是全部的故事”;常用的承上启下转移话题的短语。

词汇积累

diversity 多样性

distribute 分布

even 平均的

equivalent 等价的

reflection 反映，反射

contribute to… 导致

otherwise 否则