首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
(1)Although numbers of animals in a given region may fluctuate from year to year, the fluctuations are often temporary and, over
(1)Although numbers of animals in a given region may fluctuate from year to year, the fluctuations are often temporary and, over
admin
2022-12-18
52
问题
(1)Although numbers of animals in a given region may fluctuate from year to year, the fluctuations are often temporary and, over long periods, trivial. Scientists have advanced three theories of population control to account for this relative constancy.
(2)The first theory attributes a relatively constant population to periodic climatic catastrophes that decimate populations with such frequency as to prevent them from exceeding some particular limit. In the case of small organisms with short life cycles, climatic changes need not be catastrophic: normal seasonal changes in photoperiod (daily amount of sunlight), for example, can govern population growth. This theory—the density-independent view—asserts that climatic factors exert the same regulatory effect on population regardless of the number of individuals in a region.
(3)A second theory argues that population growth is primarily density-dependent—that is, the rate of growth of a population in a region decreases as the number of animals increases. The mechanisms that manage regulation may vary. For example, as numbers increase, the food supply would probably diminish, which would increase mortality. In addition, as Lotka and Volterra have shown, predators can find prey more easily in high-density populations. Other regulators include physiological control mechanisms: for example, Christian and Davis have demonstrated how the crowding that results from a rise in numbers may bring about hormonal changes in the pituitary (垂体) and adrenal glands (肾上腺) that in turn may regulate population by lowering sexual activity and inhibiting sexual maturation. There is evidence that these effects may persist for three generations in the absence of the original provocation. One challenge for density-dependent theorists is to develop models that would allow the precise prediction of the effects of crowding.
(4)A third theory, proposed by Wynne-Edwards and termed "epideictic", argues that organisms have evolved a "code" in the form of social or epideictic behavior displays, such as winter roosting aggregations or group vocalizing; such codes provide organisms with information on population size in a region so that they can, if necessary, exercise reproductive restraint. However, Wynne-Edwards’ theory, linking animal social behavior and population control, has been challenged, with some justification, by several studies.
Which of the following may be a density-independent factor that affects animal population?
选项
A、Famine.
B、Tornadoes.
C、The number of predators.
D、The variety of food supply.
答案
B
解析
推断题。第2段末句表明与气候有关的因素就是density-independent factors,四个选项中只有选项B表明的是某种气候因素,因此选B。其他三个选项都与气候无关,因此都不符合题意。
转载请注明原文地址:https://kaotiyun.com/show/7pcD777K
0
专业英语四级
相关试题推荐
Britain’sprivateschoolsareoneofitsmostsuccessfulexports.Thechildrenofthewealthy【C1】________tothem,whetherfromC
Asimpleideasupportsscience:"trust,butverify".Resultsshouldalwaysbe【C1】________tochallengefromexperiment.Thatsimp
Asimpleideasupportsscience:"trust,butverify".Resultsshouldalwaysbe【C1】________tochallengefromexperiment.Thatsimp
Asimpleideasupportsscience:"trust,butverify".Resultsshouldalwaysbe【C1】________tochallengefromexperiment.Thatsimp
Ifyoucan’tresistthechancetoputonabet,blameyourinsula—aregionofyourbrain.Scientiststhinkthatwhenthisbrain
Ifyoucan’tresistthechancetoputonabet,blameyourinsula—aregionofyourbrain.Scientiststhinkthatwhenthisbrain
[A]Intheory,statisticsshouldhelpsettlearguments.Theyoughttoprovidestablereferencepointsthateveryone—nomatterwh
Formorethanadecade,Dellhasposteddouble-digitgrowthbysellingcomputersdirectlytocustomers,mostofthemcorporatec
Formorethanadecade,Dellhasposteddouble-digitgrowthbysellingcomputersdirectlytocustomers,mostofthemcorporatec
[A]Airbnbisfightingtherulingwithalawsuit.Itsmainargumentindefendingitspositionascomplementaryratherthanin
随机试题
汛期将近,各单位_______于4月底前做好防洪抢险准备工作。[一定必须]
A、风湿热B、儿童类风湿C、过敏性紫癜D、先天性胸腺发育不全E、皮肤黏膜淋巴结综合征容易引起冠状动脉炎的是
A.去根B.去茎C.去核D.去毛E.去心净制诃子方法是
哺乳动物长期致癌试验结果分析指标是
A、空腹血糖B、糖基化血红蛋白C、尿糖D、胰岛素释放试验E、葡萄糖耐量试验调整胰岛素剂量最简便的检查是
某钢结构工程;施工过程中发生了以下事件。事件1:由于基础工程发生严重拖期,为了赶工,施工单位项目经理未按质量标准进行控制和检验,导致混凝土模板严重变形,为弥补缺陷,花费5万元。事件2:由于采用的水准仪不准确,导致楼面标高和层高错误,该缺陷无法弥补。根
“教,上所施,下所效也;育,养子使作善也。”对“教育”作此解释的是()
近年来公安工作的群众路线正在朝着群防群治的方向发展,这就是在党的统一领导下,动员各社会组织自觉承担治安方面的责任义务,形成全社会的社会治安综合治理网络体系。()
某公司有F、G、H、I、M和P六位总经理助理,三个部门。每一部门恰由三个总经理助理分管。每个总经理助理至少分管一个部门。以下条件必须满足:(1)有且只有一位总经理助理同时分管三个部门。(2)F和G不分管同一部门。(3)H和I不
UPS的中文译名是
最新回复
(
0
)