首页
登录
职称英语
Although numbers of animals in a given region may fluctuate from year to yea
Although numbers of animals in a given region may fluctuate from year to yea
游客
2024-01-13
31
管理
问题
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.
The first theory attributes a relatively constant population to periodic cli- matic 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.
A second theory argues that population growth is primarily density-de- pendent—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 in- crease, 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 hor- monal changes in the pituitary and adrenal glands 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.
A third theory, proposed by Wynne- Edwards and termed "epideic-tic," argues that organisms have evolved a "code"in the form of social or epideic- tic behavior displays, such as winterroosting aggregations or group vocalizing; such codes provide organisms with information on population size in a region so that they can, if necessary, ex- ercise reproductive restraint. However, Wynne-Edwards’ theory, linking animal social behavior and population control, has been challenged, with some justification, by several studies. [br] The challenge posed to the Wynne - Edwards theory by several studies is regarded by the author with
选项
A、complete indifference.
B、qualified acceptance.
C、skeptical amusement.
D、perplexed astonishment.
E、agitated dismay.
答案
B
解析
作者对那些攻击Wynne—Edwards理论的研究持何态度?原文L63—64有一句评价:“with some justification”。∴B正确。有限接受。
转载请注明原文地址:https://tihaiku.com/zcyy/3357532.html
相关试题推荐
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
DuringatriptoobservewildanimalsinAfrica,Iencounteredtheleastbrav
随机试题
[originaltext]ThereasonmyhusbandBillandIboughtavideocameraeight
WhatweretheArabmilitiasaccusedof?[br][originaltext]Sudan’sgovernm
肝浊音界扩大见于()。A.肝癌 B.肝脓肿 C.急性重型肝炎 D.多囊肝
爱因斯坦提出了光量子概念并成功地解释光电效应的规律而获得1921年的诺贝尔物理
股权投资母基金的业务不包括( )。A.一级投资 B.二级投资 C.直接投资
政府质量监督的性质属于行政执法行为,是为了保证建设工程质量,保护人民群众生命和财
共用题干 1.Someofthemostcommonlyusedm
根据房产税的相关规定,下列说法中,正确的是()。A.产权属于集体和个人所有
在项目的国民经济评价中,属于转移支付的有 A.税金B.国内银行贷款利息 C
地下水位以下或含水量超过()的土,不宜采用土桩或灰土桩。A.15% B.
最新回复
(
0
)