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
28
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).
What do desert annuals respond to as a signal for reproduction?
选项
A、Day length.
B、Sunshine.
C、Temperature.
D、Rainfall.
答案
D
解析
细节题。根据desert annuals定位到原文第三段desert annuals germinate,flower and seed whenever suitable rainfall occurs,regardless of the day length“对于沙漠里一年生植物而言,只要有合适的雨水,他们就会生长、开花、结果,不受日照长短的影响。”所以沙漠植物将雨水视为繁殖的信号,这和选项D的表述一致。
转载请注明原文地址:https://www.kaotiyun.com/show/Fzh7777K
0
大学英语六级
相关试题推荐
A、Thewomanwouldlikethemantotakecareofhermail.B、Thewomanhasputthenumberintoeveryone’smailbox.C、Thenewcopy
HarpsealsfromCanadaareshowingupintheUSwatersingreaternumbersandfarthersouththanusual,andbiologistswanttok
Caffeinewillgetyougoingduringthedaybutcouldleaveyoutossingandturningatnight—unlessyou’rea"nightowl"【B1】_____
Caffeinewillgetyougoingduringthedaybutcouldleaveyoutossingandturningatnight—unlessyou’rea"nightowl"【B1】_____
Whohasn’tbeenthere:inthethroesof(处于......的困境中)afoodcravingsointensethathavingJillianMichaelsappearintheflesh
A、Tointerviewthelocalpeople.B、Tohelpthepoorchildrenwiththeirstudy.C、Toinvestigatethehistoryoftheslums.D、Tog
A、Theparentsaren’tdoingwellinbringingtheirchildrenup.B、TVandmoviesproducetoomuchbadinfluenceonthem.C、Thepar
A、Acomparisonbetweenfishandwarm-bloodedanimals.B、Thedifferencebetweensaltwaterandfreshwaterenvironments.C、Theimpo
TheSpanish-AmericanWartookplaceinthelate1800sduringtheadministrationofPresidentWilliamMcKinley.Unlikeother
Crash.Shatter.Boom.Crash.Shatter.Boom.Smatteringofsillydialogue.Prettygirlscreams:"Dad!"Crash.Shatter.Boom.Sill
随机试题
平素头晕耳鸣,寐少梦多,与他人争吵后突发口眼喁斜,舌强语謇,半身不遂,舌红苔黄,脉弦滑,治疗选用()(2005年第62;1999年第72题)
从唯物主义历史观的角度看,“识时务者为俊杰”这里的“时务”喻指()
饮食因素致病,易致聚湿、化热、生痰的是
适用于较简单手术需血量较少的自身储血方法是
A.基托与组织不密合,卡环与基牙不贴合B.上下后牙覆盖过小C.咬合早接触,基牙负担过重D.卡环尖过长抵住了邻牙E.卡环体部进入基牙倒凹区可摘局部义齿初戴时,无法就位,其可能原因是()
项目人力资源管理的目的是调动所有项目参与人的积极性。在项目承担组织的内部和外部建立有效的工作机制,以实现()。
下列对有效市场假说描述正确的是()。Ⅰ.在市场上的每个人都是理性的经济人,金融市场上每只股票所代表的各家公司都处于这些理性人的严格监视之下Ⅱ.股票的价格反映了这些理性人的供求的平衡,想买的人正好等于想卖的人Ⅲ.股票的价格也能充分反映该资产的所
2015年1月1日,甲公司将投资性房地产从成本模式转换为公允价值模式计量。甲公司适用的所得税税率为25%,该投资性房地产的原价为40000万元,至转换时点已计提折旧10000万元,未计提减值准备,2015年1月1日,其公允价值为50000万元。甲公司按净利
一个栈的初始状态为空。现将元素1、2、3、4、5、A、B、C、D、E依次入栈,然后再依次出栈,则元素出栈的顺序是
A、 B、 C、 A根据“孩子在睡觉,请把电视的声音调低点。”可知答案为A。
最新回复
(
0
)