91.2阅读EXCEPT题，请大家进来讨论一下~~

无敌浩克OneUID: 3605802

As Gilbert White, Darwin, and others observed long ago, all species appear to have the innate capacity to increase their numbers from generation to generation. The task for ecologists is to untangle the environmental and biological factors that hold this intrinsic capacity for population growth in check over the long run. The great variety of dynamic behaviors exhibited by different populations makes this task more difficult: some populations remain roughly constant from year to year; others exhibit regular cycles of abundance and scarcity; still others vary wildly, with outbreaks and crashes that are in some cases plainly correlated with the weather, and in other cases not.
To impose some order on this kaleidoscope of patterns, one school of thought proposes dividing populations into two groups. These ecologists posit that the relatively steady populations have “density-dependent” growth parameters; that is, rates of birth, death, and migration which depend strongly on population density. The highly varying populations have “density-independent” growth parameters, with vital rates buffeted by environmental events; these rates fluctuate in a way that is wholly independent of population density.
This dichotomy has its uses, but it can cause problems if taken too literally. For one thing, no population can be driven entirely by density-independent factors all the time. No matter how severely or unpredictably birth, death and migration rates may be fluctuating around their long-term averages, if there were no density-dependent effects, the population would, in the long run, either increase or decrease without bound (barring a miracle by which gains and losses canceled exactly). Put another way, it may be that on average 99 percent of all deaths in a population arise from density-independent causes, and only one percent from factors varying with density. The factors making up the one percent may seem unimportant, and their cause may be correspondingly hard to determine. Yet, whether recognized or not, they will usually determine the long-term average population density.
In order to understand the nature of the ecologist’s investigation, we may think of the density-dependent effects on growth parameters as the “signal” ecologists are trying to isolate and interpret, one that tends to make the population increase from relatively low values or decrease from relatively high ones, while the density-independent effects act to produce “noise” in the population dynamics. For populations that remain relatively constant, or that oscillate around repeated cycles, the signal can be fairly easily characterized and its effects described, even though the causative biological mechanism may remain unknown. For irregularly fluctuating populations, we are likely to have too few observations to have any hope of extracting the signal from the overwhelming noise. But it now seems clear that all populations are regulated by a mixture of density-dependent and density-independent effects in varying proportions.

23.        In the passage, the author does all of the following EXCEPT:
(A) cite the views of other biologists
one school of thought proposes dividing populations into two groups.
(B) define a basic problem that the passage addresses
The great variety of dynamic behaviors exhibited by different populations makes this task more difficult
This dichotomy has its uses
(C) present conceptual categories used by other biologists
(D) describe the results of a particular study
(E) draw a conclusion
they will usually determine the long-term average population density.

问题主要集中在C 和 D上
conceptual categories是具体指什么呢？
D：these rates fluctuate in a way that is wholly independent of population density.
这个结论虽然不完全正确，但是不算是研究结果吗？

cchen2014UID: 3590105

These ecologists posit that the relatively steady populations have “density-dependent” growth parameters; that is, rates of birth, death, and migration which depend strongly on population density. The highly varying populations have “density-independent” growth parameters, with vital rates buffeted by environmental events; these rates fluctuate in a way that is wholly independent of population density.
后面都是posit出来的东西， 不是研究结果

无敌浩克OneUID: 3605802

cchen2014 发表于 2015-5-23 12:20
These ecologists posit that the relatively steady populations have “density-dependent” growth para ...

posit的功效到句号还没结束吗？怎么判断呀？

wfxmfwjwUID: 3582171

我怎么觉的A是As Gilbert White, Darwin, and others observed long ago, all species appear to have the innate capacity to increase their numbers from generation to generation.
C是These ecologists posit that the relatively steady populations have “density-dependent” growth parameters; that is, rates of birth, death, and migration which depend strongly on population density. The highly varying populations have “density-independent” growth parameters, with vital rates buffeted by environmental events; these rates fluctuate in a way that is wholly independent of population density.这个
但是没有D

无敌浩克OneUID: 3605802

wfxmfwjw 发表于 2015-5-23 17:20
我怎么觉的A是As Gilbert White, Darwin, and others observed long ago, all species appear to have the  ...

conceptual categories是具体指什么呢？

wfxmfwjwUID: 3582171

density-dependent   density-independent

far2goUID: 3568511

我准备明天开始练阅读, 你是写一篇对一篇呢,还是连续写几篇再对?

无敌浩克OneUID: 3605802

wfxmfwjw 发表于 2015-5-23 19:50
density-dependent   density-independent

soga!!谢谢~~！

无敌浩克OneUID: 3605802

far2go 发表于 2015-5-23 21:34
我准备明天开始练阅读, 你是写一篇对一篇呢,还是连续写几篇再对?

不一定啊~加油！

far2goUID: 3568511

无敌浩克One 发表于 2015-5-24 10:07
不一定啊~加油！

不是推荐用五步法训练吗,我在思考要怎么处理, 然后我用economist blog 训练就没问题了, 如果阅读题的话感觉不太好.

wsjenglishUID: 3643341

D：没有一个particular study, 都是泛泛的说