首页
登录
职称英语
(1)Although numbers of animals in a given region may fluctuate from year to
(1)Although numbers of animals in a given region may fluctuate from year to
游客
2024-09-10
49
管理
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. [br] According to the Wynne-Edwards’ theory, epideictic behavior displays serve the function of ______.
选项
A、determining roosting aggregations
B、locating food
C、attracting predators
D、regulating sexual activity
答案
D
解析
末段首句是一个长难句,句末的结果从句表明生物体类似社会或传播行为的信号的功能,选项D表达了相同的功能,因此选D。
转载请注明原文地址:http://tihaiku.com/zcyy/3751913.html
相关试题推荐
(1)Althoughnumbersofanimalsinagivenregionmayfluctuatefromyearto
Bycuttingdowntreeswe______thenaturalhomeofbirdsandanimals.A、harmB、h
AlthoughIlikedtheappearanceofthehouse,whatreallymademedecidetobuy
[originaltext]W:Frank,wejustgotoursalesfiguresinandthenumbersareve
Acutehearinghelpsmostanimalssensetheapproachofthunderstormslongbefor
______,Mr.Wellsisscarcelyinsympathywiththeworkingclass.A、Althoughhei
Mendifferfromanimals______theycanthinkandspeak.A、forwhichB、forthatC
TheTibetAutonomousRegionis1.22millionsq.km.inarea,withanaverage____
Althoughshe’sa(n)______talenteddancer,shestillpracticesseveralhourseve
______atinthisway,theairpollutioninthisregiondoesn’tseemsoserious.
随机试题
Mr.Greenoftenhassupperathome,______?A、hasn’theB、hasn’tMr.GreenC、doe
大多数人都认同骑自行车环保并且能够有效避免交通拥堵的观点。然而,他们依然有充分的理由放弃骑自行车出行。最明显的理由是公共交通很便利。然而最重要的原因是他
Doppelganger,aSanFrancisco-basedstartupislaunchingavirtualworldtoday
AnexplosionhadthrownradiomanHarleyOlsonoutofbed.Heworkedwildly,
建筑工程量清单中规定砌筑实心墙凸出墙面但不能增加计算工程量,并入墙体的砌体是(
孕前体重正常,不计划哺乳的女性,其适宜的孕期增重为( )kg。A.10 B.
胚胎期形成唇裂畸形的时期是A、第2~4周 B、第6~8周 C、第12~14周
FA0的“食品法典委员会”制定的农产品质量标准可被看作是( )。A.专用标准
下列施工过程中,作为建造类施工过程而必须列入流水施工进度计划之中的有()。
小脑出血的常见表现为() A.眩晕、频繁呕吐、头痛、病变侧共济失调 B.意识
最新回复
(
0
)