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
Breeding in most organisms occurs during a part of the year only, and so a reliable cue is needed to trigger breeding behaviour.
Breeding in most organisms occurs during a part of the year only, and so a reliable cue is needed to trigger breeding behaviour.
admin
2014-12-26
50
问题
Breeding in most organisms occurs during a part of the year only, and so a reliable cue is needed to trigger breeding behaviour. Day length is an excellent cue, because it provides a perfectly predictable pattern of change within a year. In the temperate zone in spring, temperatures fluctuate greatly from day to day, but day length increases steadily by a predictable amount. The seasonal impact of day length on physiological responses is called photoperiodism, and the amount of experimental evidence for this phenomenon is considerable. For example, some species of birds’ breeding can be induced even in midwinter simply by increasing day length artificially(Wolfson 1964). Other examples of photoperiodism occur in plants. A short-day plant flowers when the day is less than a certain critical length. A long-day plant flowers after a certain critical day length is exceeded. In both cases the critical day length differs from species to species. Plants which flower after a period of vegetative growth, regardless of photoperiod, are known as day-neutral plants.
Breeding seasons in animals such as birds have evolved to occupy the part of the year in which offspring have the greatest chances of survival. Before the breeding season begins, food reserves must be built up to support the energy cost of reproduction, and to provide for young birds both when they are in the nest and after fledging. Thus many temperate-zone birds use the increased day lengths in spring as a cue to begin the nesting cycle, because this is a point when adequate food resources will be assured.
The adaptive significance of photoperiodism in plane is also clear. Short-day plane that flower in spring in the temperate zone are adapted to maximising seedling growth during the growing season. Long-day plants are adapted for situations that require fertilization by insects, or a long period of seed ripening. Short-day plane that flower in the autumn in the temperate zone are able to build up food reserves over the growing season and over winter as seeds. Day-neutral plane have an evolutionary advantage when the connection between the favourable period for reproduction and day length is much less certain. For example, desert annuals germinate, flower and seed whenever suitable rainfall occurs, regardless of the day length.
The breeding season of some plants can be delayed to extraordinary lengths. Bamboos are perennial grasses that remain in a vegetative state for many years and then suddenly flower, fruit and die(Evans 1976). Every bamboo of the species Chusquea abietifolio on the island of Jamaica flowered, set seed and died during 1884. The next generation of bamboo flowered and died between 1916 and 1918, which suggests a vegetative cycle of about 31 years. The climatic trigger for this flowering cycle is not-yet known, but the adaptive significance is clear. The simultaneous production of masses of bamboo seeds(in some cases lying 12 to 15 centimetres deep on the ground)is more than all the seed-eating animals can cope with at the time, so that some seeds escape being eaten and grow up to form the next generation(Evans 1976).
Which of the followings is an example of the plants whose breeding season can be delayed for a very long time?
选项
A、Shade-tolerant plants.
B、Bamboos.
C、Day-neutral plants.
D、Desert annuals.
答案
B
解析
细节题。根据breeding season、delayed定位到最后一段The breedingseason of some plants can be delayed to extraordinary lengths.Bamboos are perennialgrasses that remain in a vegetative state for many years and then suddenly flower,fruitand die.“一些植物的生殖期会拖得特别长。竹子是多年生植物,在很多年的时间里都保持生长状态,然后突然开花、结果、死亡。”所以答案选B。
转载请注明原文地址:https://kaotiyun.com/show/Gzh7777K
0
大学英语六级
相关试题推荐
HarpsealsfromCanadaareshowingupintheUSwatersingreaternumbersandfarthersouththanusual,andbiologistswanttok
Caffeinewillgetyougoingduringthedaybutcouldleaveyoutossingandturningatnight—unlessyou’rea"nightowl"【B1】_____
Whohasn’tbeenthere:inthethroesof(处于......的困境中)afoodcravingsointensethathavingJillianMichaelsappearintheflesh
A、Theyimposethreattothelocaleconomy.B、Theyenrichlocalspecies.C、Theybecomealocaltouristattraction.D、Theykilllo
A、Acomparisonbetweenfishandwarm-bloodedanimals.B、Thedifferencebetweensaltwaterandfreshwaterenvironments.C、Theimpo
A、Thereasonsforpeople’sbehavior.B、Commonreasonsforanger.C、Waystochangepeople’sattitudes.D、Theeffectsofnegative
A、She’slookingforwardtoherweekendtrip.B、She’dliketoinvitethemantogotheretogether.C、Shewouldprefertogototh
A、Anewsreporttheyarelisteningto.B、Amagazinethewomanisreading.C、ATVseriesaboutfinance.D、Atextbookoneconomy.
A、Shedoessometeachingwork.B、Shedoesherhomework.C、Sheworksasababysitter.D、Sheattendsweekendlessonstoimprovehe
TheAmericaneconomicsystemisorganizedaroundabasicallyprivateenterprise.It’s【B1】______economyinwhichconsumersdeterm
随机试题
通过经常性的各种有效信息的传递,使组织成员建立密切关系,体现了协调的
患者女性,23岁。停经48天,阴道少量流血1天。晨4时突发下腹剧痛,伴恶心、呕吐及一过性晕厥。面色苍白,血压70/40mmHg,脉搏126次/分,妇科检查:阴道畅,有少量血液,宫颈举痛明显,后穹隆触痛(+),盆腔触诊不满意,尿妊娠试验弱阳性。护士在
区房管局向某公司发放房屋拆迁许可证。被拆迁人王某向区房管局提出申请,要求公开该公司办理拆迁许可证时所提交的建设用地规划许可证,区房管局作出拒绝公开的答复。对此,下列哪一说法是正确的?()(司考2010.2.45)
代理记账人员必须遵守的规则有()。
运用市场法时选择3个及3个以上参照物的目的是()。
某企业现有资金100000元,可用于以下投资方案:方案一:购入国库券(5年期,年利率14%,不计复利,到期一次支付本息);方案二:购买新设备(使用期5年,预计残值收入为设备总额的10%,按直线法计提折旧,设备交付使用后每年可以实现12000元的息税
一位教育工作者的真正威信在于他的__________,它会对学生产生终身影响。
记忆过程包括以下哪几个基本环节?()
依次填人下面一段文字横线处的语句,衔接最恰当的一项是:标点是辅助文字记录语言的符号,是书面语的有机组成部分。标点符号有狭义和广义之分:______。①狭义指约定俗成的、有别于文字的书写符号,如句号、问号、逗号、分号等②而标点则有
2019年1月2日,习近平在《告台湾同胞书》发表40周年纪念会上指出,“世界上只有一个中国,坚持一个中国原则是公认的国际关系准则,是国际社会的普遍共识。”下列关于两岸关系的历史和未来,判断正确的是()
最新回复
(
0
)