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
The livelihood of each species in the vast and intricate assemblage of living things depends on the existence of other organisms
The livelihood of each species in the vast and intricate assemblage of living things depends on the existence of other organisms
admin
2016-11-21
58
问题
The livelihood of each species in the vast and intricate assemblage of living things depends on the existence of other organisms. This interdependence is sometimes subtle, sometimes obvious. Perhaps the most straightforward dependence of one species on another occurs with parasites, organisms that live on or in other living things and derive nutrients directly from them. The parasitic way of life is widespread. A multitude of microorganisms(including viruses and bacteria)and an army of invertebrates — or creatures lacking a spinal column(including insects and many different types of worms)— make their livings directly at the expense of other creatures. In the face of this onslaught, living things have evolved a variety of defense mechanisms for protecting their bodies from invasion by other organisms.
Certain fungi and even some kinds of bacteria secrete substances known as antibiotics into their external environment. These substances are capable of killing or inhibiting the growth of various kinds of bacteria that also occupy the area, thereby eliminating or reducing the competition for nutrients. The same principle is used in defense against invaders in other groups of organisms. For example, when attacked by disease-causing fungi or bacteria, many kinds of plants produce chemicals that help to ward off the invaders.
Members of the animal kingdom have developed a variety of defense mechanisms for dealing with parasites. Although these mechanisms vary considerably, all major groups of animals are capable of detecting and reacting to the presence of "foreign" cells. In fact, through the animal kingdom, from sponges to certain types of worms, shellfish, and all vertebrates(creatures possessing a spinal column), there is evidence that transplants of cells or fragments of tissues into an animal are accepted only if they come from genetically compatible or closely related individuals.
The ability to distinguish between " self" and " nonself" , while present in all animals, is most efficient among vertebrates, which have developed an immune system as their defense mechanism. The immune system recognizes and takes action against foreign invaders and transplanted tissues that are treated as foreign cells.
Plants defend themselves against invaders by producing______.
选项
A、antibiotics
B、chemicals
C、fungi
D、bacteria
答案
B
解析
事实细节题。本题答案可以从…many kinds of plants produce chemicals that help to ward off the invaders中得出。
转载请注明原文地址:https://www.kaotiyun.com/show/UTJK777K
0
专业英语四级
相关试题推荐
MostpeopleknowtwothingsaboutCorsica;Napoleonwasbornhereanditwasthehauntofbandits.Thefirstiscorrect;thesec
Studentloansarebasedonasimpleidea:thatagraduate’sfutureflowofearningswillmorethancoverthecostsofdoingade
Studentloansarebasedonasimpleidea:thatagraduate’sfutureflowofearningswillmorethancoverthecostsofdoingade
Americansoftensaythatthereareonlytwothingsapersoncanbesureofinlife:deathandtaxes.Americansdonothaveacor
Thestatistics______thatlivingstandardsintheareahaveimproveddrasticallyinrecenttimes.
Therearestillmanyproblemsaheadofus,butbythistimenextyearwecanseelightattheendofthe______.
Thefutureofthecompanyisatstake;manyofitstalentedemployeeshaveresignedfromthecompany.Theunderlinedpartsmeans
Thestatistics______thatlivingstandardsintheareahaveimproveddrasticallyinrecenttimes.
随机试题
易化扩散和主动转运的共同特点是
肝郁血虚,脾失健运。见两胁作痛,神疲食少,脉虚弦者,治宜选用
患者,男,65岁。有慢性咳喘病史20年,咳嗽、咳喘加重2周,咳大量白色泡沫痰,气短喘息,活动后加重,脘痞纳少,倦怠乏力。体格检查:神志清楚,舌质淡红,苔薄腻,脉促,桶状胸,剑突下可见心尖搏动,双肺可闻及湿啰音。心率110次/分,节律不齐,心音强弱不等。心电
下列结构的药物名称为
下列关于金属结构工程的工程量计算的说法,正确的为()。
气体灭火系统灭火剂输送管道的外表面宜涂红色油漆。在吊顶内、活动地板下等隐蔽场所内的管道,可涂红色油漆色环,色环宽度不应小于()mm,且每个防护区或保护对象的色环宽度要一致,间距应均匀。
以下各项中,用人单位可以单方随时解除劳动合同的是()。
孙悟空:《西游记》:吴承恩
______almosthadnointertribalwarfare?______wasthenameformanytribesunitedindefendingtheirlandsandinwarfare?
A、unbelievableB、confusingC、surprisedD、baffledB观点态度的找寻和判断。根据原文WhyCambridgeshouldtopsuchanunhealthyleaguetablehasbaf
最新回复
(
0
)