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
Disease can be one of the most powerful factors in checking population growth. In crowded conditions where many individuals of a
Disease can be one of the most powerful factors in checking population growth. In crowded conditions where many individuals of a
admin
2013-04-08
88
问题
Disease can be one of the most powerful factors in checking population growth. In crowded conditions where many individuals of a species are living close together, the spread of pathogens (病原体) from one individual to another, occurs readily. History shows many instances where human populations, crowded together in cities, have been almost wiped out by the rapid spread of disease. Modern orchard and forestry practice recognizes this fact and the close planting of trees of the same species is avoided. Mixed forests and orchards are the recognized procedure these days.
Apart from regulating population numbers in other species, disease has probably been the greatest factor in controlling the growth of the human population.
In the mid 14th century, the Black Death wiped out 25 million people in Europe alone, while as recently as 1918 over 21 million people died in a single year as a result of the influenza epidemic. The relative stability of the human population has been upset by advances in medical science. No longer does disease regulate human population growth in many parts of the world. Medical cures have prolonged life and upset the age structure of many populations, increasing the proportion of individuals in the reproductive age group.
The decrease in distribution and numbers of some species of native birds in New Zealand-the bellbird for example-has been attributed to disease rather than predation. Indeed, there are examples to show that disease has deliberately been used to control some animal populations. In Australia, for instance, the introduction of the myxomatosis (多发粘液瘤病) virus has drastically reduced the rabbit population in many areas, although increasing resistance to the disease is becoming apparent. Attempts to introduce myxomatosis into New Zealand as a means of rabbit population control have failed, mainly because the species of flea and mosquito that transmit the disease are absent in this country.
Research is currently being carried out to discover whether selected strains of virus can be used to control pathogenic bacteria that have developed a resistance to drugs. It is hoped that the virus will parasite (寄生) and kill the bacteria without harming the organism that the bacteria has infected.
The relative stability of the human population has been upset by ______.
选项
A、the proportion of the reproductive age group
B、the influenza epidemic
C、advances in medical science
D、the Black Death in Europe
答案
C
解析
见第三段“The relative stability of the human population has been upset by advances in medical science.”
转载请注明原文地址:https://kaotiyun.com/show/t4r7777K
0
大学英语四级
相关试题推荐
Today,Americanfilmmakersproducemovieswithfewrestraintsaboutviolence,sexualityandadultlanguage.Butthiswasnotalw
Asresearcherslearnmoreabouthowchildren’sintelligencedevelops,theyareincreasinglysurprisedbythepowerofparents.T
______(当说到能源安全),ourpolicyisnotdirectedagainstanysinglecountry.
Inpreviousgenerations,youngpeoplewereundertheirparents’control;nowtheteenagechildrenoftheWest’srichestgenerat
Thoughitisamereonetothreepercentofthepopulation,theupperclasspossessesatleast25percentofthenation’swealth
TheNationalTrustinBritainplaysanincreasinglyimportantpartinthepreservationforpublicenjoymentofthebestthatis
A、Artists.B、TourguidesC、Grocers.D、Musicians.DWhogaveNewYorkitsnickname?
Therewerethreedifferentkindsof【B1】______guides.Onekind,atourist【B2】______,mightmeettouristsattheairport.Hemight
A、Becauseallthebuildingsinthecitylookalike.B、Becausetherearenosignstodirectthem.C、Becausenotourguidesareav
随机试题
如人工周期有经血来潮,为鉴别诊断需进行如下辅助检查,但不包括:如测定FSH74U/L,LH41U/L,E2<0.1pmol/L,T正常女性范围,可能的原因为:
下列哪项指标常提示狼疮活动
报关企业________,海关可以暂停其从事报关业务。
某传真机公司每年购买80000个用于制造传真机的调制解调器,每个解调器的成本为10元,一年解调器的持有成本为3元,每批的订货成本为30元,最近该公司与其供应商准备开始联合库存的管理尝试,力图降低整个供应链的成本,提高竞争力。请分析下列问题:
简述国务院银行业监督管理机构的权利与义务。
常某于2015年1月18日向国家知识产权局提交了一件实用新型专利申请,该申请享有2014年8月20日的优先权日,后发现所提交申请遗漏了附图2,而说明书中写有对该附图2的说明,常某于2015年3月18日补交了附图2,经审查国家知识产权局接受了该附图2,该申请
发展社会主义文化的根本任务是()。
平均报酬率
论述开元之治的措施及意义
软件生命周期可分为定义阶段、开发阶段和维护阶段,下面属于定义阶段任务的是
最新回复
(
0
)