月日托福阅读真题回顾及解析.doc

2012年5月12日托福阅读真题回顾及解析 　　TOPIC 1玛雅文明及其衰败 　　考生回忆： 　　玛雅文明曾经辉煌； 　　衰落原因：战争；气候；不合理耕作 　　Non-ecological theories of Maya decline are divided into several subcategories, such as overpopulation, foreign invasion, peasant revolt, and the collapse of key trade routes. Ecological hypotheses (theories) include environmental disaster, epidemic disease, and climate change. There is evidence that the Maya population exceeded the carrying capacity of the environment including exhaustion of agricultural potential and overhunting of the large animals in the area. Some scholars have recently theorized that an intense 200 year drought led to the collapse of Maya civilization. 　　TOPIC 2生态区间与资源共享 　　考生回忆： 　　若资源有限：共同依赖该资源的生物会竞争，只有一种存活； 　　若资源充足：不竞争，都存活。 　　实验证明以上：在一个试管（tube）里养两种生命体（organism），结果最后只有一种存活了。得出结论两种竞争的生物在资源有限的同一时间同一环境下不能同时存活。第二次实验，把两种生物分别放在试管底部（tube bottom）和溶液（solution）表面，结果它们就都存活了，因为它们不争资源。 　　后来就说这种现象还能涉及多种物种。如某个地方有好几种鸟，它们都吃一样的虫子，每种飞的时候都结伙（flock），不过它们会在不同的时间迁徙（migrate）。它们共同生存，研究发现它们在树的canopy上都有自己的地盘，在不同的位置，所以互不影响。 　　The term niche differentiation as it applies to the field of ecology, refers to the process by which natural selection drives competing species into different patterns of resource use or different niches. This process allows two species to partition certain resources so that one species does not out-compete the other. Thus, coexistence is obtained through the differentiation of their realized ecological niches. 　　Spatial resource partitioning occurs when two competing species use the same resource by occupying different areas or habitats within the range of occurrence of the resource. Spatial partitioning can occur at small scales (microhabitat differentiation) or at large scales (geographical differentiation). Microhabitat differentiation occurs when two competing species with overlapping home ranges partition a resource. Two examples would be different species of fish feeding at different depths in a lake or different species of monkey feeding at different heights in