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Dendrochronology, the study of tree-ring records to glean information about the past, is possible because each year a tree adds a new layer of wood between the existing wood and the bark. In temperate and subpolar climates, cells added at the growing season's start are large and thin-walled, but later the new cells that develop are smaller and thick-walled; the growing season is followed by a period of dormancy(冬眠,隐匿). When a tree trunk is viewed in cross section, a boundary line is normally visible between the small-celled wood added at the end of the growing season in the previous year and the large-celled spring wood of the following year's growing season. The annual growth pattern appears as a series of larger and larger rings. In wet years rings are broad; during drought years they are narrow, since the trees grow less. Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions.
However, trees that grew in areas with a steady supply of groundwater show little variation in ring width from year to year; these "complacentrings tell nothing about changes in climate. And trees in extremely dry regions may go a year or two without adding any rings, thereby introducing uncertainties into the count. Certain species sometimes add more than one ring in a single year, when growth halts temporarily and then starts again.
Question #50. 341-02 (23608-!-item-!-188;#058&000341-02)
The passage suggests which of the following about the ring patterns of two trees that grew in the same area and that were of different, but overlapping, ages?
(A) The rings corresponding to the overlapping years would often exhibit similar patterns. (B) The rings corresponding to the years in which only one of the trees was alive would not reliably indicate the climate conditions of those years. (C) The rings corresponding to the overlapping years would exhibit similar patterns only if the trees were of the same species.-我选C,从第一段句尾知会表现相同,但是最后一段句尾又说不同树种表现也会不同,所以综合两个我选了C,但答案是A,不理解,觉得没C全面 (D) The rings corresponding to the overlapping years could not be complacent rings. (E) The rings corresponding to the overlapping years would provide a more reliable index of dry climate conditions than of wet conditions.
Question #51. 341-03 (23654-!-item-!-188;#058&000341-03)
In the highlighted text, "uncertainties" refers to的
(A) dendrochronologists' failure to consider the prevalence of erratic weather patterns (B) inconsistencies introduced because of changes in methodology (C) some tree species' tendency to deviate from the norm (D) the lack of detectable variation in trees with complacent rings (E) the lack of perfect correlation between the number of a tree's rings and its age -答案选E,但是我错选了C,感觉都是说年轮和气候的关系,跟树龄没关系吧
Question #52. 341-04 (23700-!-item-!-188;#058&000341-04)C
The passage is primarily concerned with
(A) evaluating the effect of climate on the growth of trees of different species (B) questioning the validity of a method used to study tree-ring records (C) explaining how climatic conditions can be deduced from tree-ring patterns (D) outlining the relation between tree size and cell structure within the tree (E) tracing the development of a scientific method of analyzing tree-ring patterns 答案选C,我选B,我认为段首先提出树龄法这个东西,然后阐述这个原理,第2段用however否定其准确性啊。
还有4天就考试了 这篇阅读我全部做错,而且看了答案还是不能理解,期望牛牛解答,感激不尽! |
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