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
2024-10-19
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 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.
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.
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, if true, would best support the density-dependent theory of population control?
选项
A、As the number of foxes in Minnesota decrease, the growth rate of this population of foxes begins to increase.
B、As the number of woodpeckers in Vermont decreases, the growth rate of this population of woodpeckers also begins to decrease.
C、After the number of prairie dogs in Oklahoma increases, the number of predators of these dogs also begins to increase.
D、After the number of beavers in Tennessee decreases, the number of predators of these beavers begins to increase.
答案
A
解析
推断题。根据第3段首句描述the rate of growth of a population和the number of animals之间的关系可知:前者减,后者便增;前者增,后者便减。只有选项A描述的关系符合原文,由此可判定选项A为本题答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3807691.html
相关试题推荐
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
AlthoughIaminperfecthealth,andinpossessionofavalidclass-oneCali
随机试题
Thevastprojecthasbeencomparedwiththe【B1】______oftheEgyptianPyramidsor
【B1】[br]【B20】A、pleasureB、propertyC、interestsD、opportunitiesA此句照应了文章首句。商人变得
项目绩效评审的主要目标是()。A.根据项目的基准计划来决定完成该项目需要多少资
男性,在聚餐饮酒后3小时于凌晨出现头痛,头晕,乏力,意识模糊,呼吸急促,眼前有闪
某男子因车祸受重伤被送到医院急救,因没带押金,医生拒绝为其办理住院手续,当病人家
共用题干 张某欲购买一套住房,委托甲房地产经纪机构(以下简称甲机构)寻找房源并
下列关于卖方代理的表述中,错误的是()。(2009年真题)A.代理方要帮助委
Thechangeinthatvillagewasmiraculou
(2018年真题)下列占用耕地的情形中,应减征耕地占用税的是()。A.医院占用
关于效力待定合同的说法,正确的是()。A.善意相对人不可撤销效力待定合同 B
最新回复
(
0
)