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
149
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.
Why did the introduction of myxomatosis into New Zealand as a means of rabbit control fail?
选项
A、Because the nature of myxomatosis is evil.
B、Because the species of flea and mosquito that transmit the disease are absent in this country.
C、Because there are too many rabbits.
D、Because the myxomatosis virus bas drastically reduced.
答案
B
解析
见文中mainly because the species of flea and mosquito that transmit the disease are absent in this country.
转载请注明原文地址:https://kaotiyun.com/show/34r7777K
0
大学英语四级
相关试题推荐
Immigrantsarepeoplewholeaveonecountryto_________________________(永久地住在另一个国家).
A、Colleagues.B、Bossandsecretary.C、Customerandclientmanager.D、Husbandandwife.C
However______certainnaturalresourcesmaybe,theycannotreproducethemselvesandareboundtobeusedupultimately.
AGrassrootsRemedyMostofusspendourlivesseekingthenaturalworld.Tothisend,wewalkthedog,playgolf,gofishin
Thoughitisamereonetothreepercentofthepopulation,theupperclasspossessesatleast25percentofthenation’swealth
A、Atanairport.B、Ataboatdock.C、Ataweatherstation.D、Atabeach.A由女士说的haveagoodflight可知男士即将乘飞机。所以对话最可能发生在机场,故A正确。
Weoftenhearthe【B1】______,"Everybodytalksaboutweather,butnobodydoesanythingaboutit."Thisisreallynot【B2】______to
A、Toatapeshop.B、Toaparty.C、Toaconcert.D、ToattendameetingC对话中,男士说他不得不去参加会议,但其实他更愿意和女士一起去听音乐会,女士也感到很遗憾,因为男士最喜欢的乐队将会在
Unlessmeasuresaretakenatonce,thereisapossibilitythatalltheoceansoftheworldwillbedeadbythenextcentury.How
Intheseventeenthcentury,tipwasprobablyawordusedby______.Whichofthefollowingwordscanbestdescribethegovernme
随机试题
破伤风发病是由于
抢救伤员时应当首先处理
护士协助患者更换卧位,不正确的操作是
我国《选举法》中规定,省、自治区的人民代表大会代表的名额,由本级人民代表大会常务委员会按照农村每一代表所代表的人口数四倍于城市每一代表所代表的人口数的原则分配。当前,有人对该规定提出了质疑,认为它违反了宪法上的平等原则,也有人认为该规定是合理的。 请你运
以工业产权和非专利技术作价出资的比例一般不超过项目资本金总额的()。
本着既经济合理又能确保消防安全基本要求的原则,对临时搭建的宿舍、办公用房的要求有()。
对供应链金融模式下的存货和应收账款,贷后管理应关注的内容包括()。
旅游者的个别要求如果是因为客观因素的局限而难以满足,导游员应遵循的原则是()。
张老师与李老师在教学研讨会上展开了一场辩论,张老师认为教学应以学生掌握理论知识为目的,调动学生理性思维的运转及发展,是一种理性运动。李老师则认为教学重在学生的情感体验和意志锻炼,是一种情意活动。他们之间的辩论实质上属于()的辩论。
将考生文件夹下的SNOW文件夹中的文件夹DRIGEN删除。
最新回复
(
0
)