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
2024-08-31
41
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] 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://tihaiku.com/zcyy/3738167.html
相关试题推荐
Althoughitseemedtotakeallherstrength,thepatient______upasmiletohe
Bothpropertiesoccupyaregionlongknownasthe"lungofHaikou"foritsgreen
_______,hesometimescannotstandthewayshesolvesproblems.A、Althoughmuch
Enginesaretomachines______heartsaretoanimals.A、thatB、whichC、whenD、wha
Althoughitseemedtotakeallherstrength,thepatient______upasmiletoher
______,hesometimescannotstandthewayshesolvesproblems.A、Althoughmuchh
It’s______thecaseintheregion;astoryalwayssoundsclearenoughatadist
(1)Naturally,inagroupofanimalsasdiverseasthesnakes,andwithsoma
(1)Althoughnumbersofanimalsinagivenregionmayfluctuatefromyearto
(1)Althoughnumbersofanimalsinagivenregionmayfluctuatefromyearto
随机试题
ALetterofInvitationForthispart,youareallowed30minutestowritea
Thermoelectricmaterialscanconvertwasteheatdirectlyintoelectricity.T
以下不属于基金销售机构的是( )。A.商业银行 B.证券公司 C.中国结算
根据《公开地图内容表示补充规定(试行)》,关于利用涉及国家秘密的测绘成果编制的公
根据以下材料,回答题 某新入市投资者在其保证金账户中存入保证金20万元。当日开
一患者进行金属烤瓷冠修复,冠就位后发现冠十分密合,经调无早接触后选择聚羧酸粘固剂
抗菌药物的临床使用应当遵循下列的原则中,哪项是正确的A.安全、有效 B.安全、
下列属于绩效考核指标体系的内容的是()。A.绩效考核指标 B.绩效考核指标权
编制借款还本付息计划表时,需要直接引用的数据报表有()。A:流动资金估算表 B
A.肺动脉瓣区第二心音增强伴分裂 B.主动脉瓣区第二心音增强 C.第一心音分
最新回复
(
0
)