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alatino Linotype";">OG12 P360 alatino Linotype";">A recent study has provided clues to alatino Linotype";">predator-prey dynamics in the late Pleistocene alatino Linotype";">era. Researchers compared the number of tooth alatino Linotype";">fractures in present-day carnivores with tooth alatino Linotype";">fractures in carnivores that lived 36,000 to 10,000 alatino Linotype";">years ago and that were preserved in the Rancho alatino Linotype";">La alatino Linotype";">Breaalatino Linotype";"> tar pits in Los Angeles. The breakage frequencies in the extinct species were strikingly higher than those in the present-day species.
In considering possible explanations for this finding, the researchers dismissed demographic bias because older individuals were not overrepresented in the fossil samples. They rejected preservational bias because a total absence of breakage in two extinct species demonstrated that the fractures were not the result of abrasion within the pits. They ruled out local bias because breakage data obtained from other Pleistocene sites were similar to the La Brea data. The explanation they consider most plausible is behavioral differences between extinct and present-day carnivores—in particular, more contact between the teeth of predators and the bones of prey due to more thorough consumption of carcasses by the extinct species. Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities.
7. The researchers’ conclusion concerning the absence of demographic bias would be most seriously undermined if it were found that (A) the older an individual carnivore is, the more likely it is to have a large number of tooth fractures (B) the average age at death of a present-day carnivore is greater than was the average age at death of a Pleistocene carnivore (C) in Pleistocene carnivore species, older individuals consumed carcasses as thoroughly as did younger individuals (D) the methods used to determine animals’ ages in fossil samples tend to misidentify many older individuals as younger individuals (E) data concerning the ages of fossil samples cannot provide reliable information about behavioral differences between extinct carnivores and present-day carnivores 能不能帮我翻译一下这道题的题目，尤其是那个the absence of demographic bias 搞得我不明白是要削弱db加强作者，还是削弱作者加强db… 麻烦大家说一下思考的思路吧，谢谢咯~~~(*^__^*) 以下是解释 Logical structure Begin by looking at the section on demographic bias. Lines 11–13 state that demographic bias has been ruled out as an explanation because older individuals were not overrepresented in the fossil samples. Th is implies that older carnivores would be expected to have more tooth fractures than younger ones. To answer this question, read each answer choice to find the one statement that undermines the researchers’ conclusion. If the method to determine age in the fossil samples is faulty and older carnivores are misidentified as younger ones, then demographic bias cannot be dismissed. A Th is statement supports rather than undermines the researchers’ conclusion. B Th is comparison between present-day and Pleistocene carnivores has no bearing on whether older Pleistocene individuals were overrepresented or not. C Th e comparison between older and younger individuals is irrelevant to the researchers’ conclusion. D Correct. If older individuals have been misidentified as younger ones, then a higher proportion of older individuals undermines the researchers’ conclusion. E Neither the diff erences nor the data are relevant to the researchers’ conclusion about the proportion of older Pleistocene carnivores. | 
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发表于 2009-9-7 22:31:00
