问题 解答题

养蚕织丝在我国有着悠久的历史.如图表示桑蚕的不同发育时期,请回答下列问题:

(1)从图中看出,蚕的发育经历______时期,这种发育过程从幼体到成体有较大的变化,称为______.

(2)蚕的体细胞中有28对染色体,它产生的精子或卵细胞中染色体的数目是______.

(3)课外养蚕小组的同学发现,黄足蚕结黄茧,白足蚕结白茧.他们选用黄足蚕与白足蚕杂交,后代全是黄足蚕,说明黄足是______性状;如果控制相对性状的基因用A、a表示,则亲代蚕和子代蚕的基因组成分别是______;若让子代蚕与白足蚕杂交,推测后代黄足蚕和白足蚕的比例是______.

(4)2008年,我国的桑蚕育种专家将水母的绿色荧光蛋白基因转移到桑蚕的体内,培育出能吐绿色荧光蚕丝的新品种.这项现代生物技术称为______,这个事例说明基因与性状的关系是______.

(5)蚕与人类的关系非常密切,请你列举两个事例:______.

答案

(1)家蚕的生殖发育经过受精卵、幼虫、蛹和成虫等4个时期的叫完全变态发育.完全变态发育的幼虫与成虫在形态构造和生活习性上明显不同,差异很大.

(2)体细胞形成生殖细胞时,染色体的数目要减少一半

(3)黄足蚕与白足蚕杂交,后代全是黄足蚕,说明黄足是显性性状;如果控制相对性状的基因用A、a表示,则亲代蚕和子代蚕的基因组成分别是;AA和aa、Aa若让子代蚕与白足蚕杂交,推测后代黄足蚕和白足蚕的比例是1:1

(4)2008年,我国的桑蚕育种专家将水母的绿色荧光蛋白基因转移到桑蚕的体内,培育出能吐绿色荧光蚕丝的新品种.这项现代生物技术称为转基因技术,这个事例说明基因与性状的关系是基因控制生物的性状.

(5)蚕与人类的关系非常密切:蚕丝为人类提供丝织品;蚕蛹可供食用;蚕是中外文化交流--丝绸之路的重要基础;蚕赋予诗人灵感,形成脍炙人口的诗篇等等

故答案为:

(1)卵、幼虫、蛹和成虫;完全变态

(2)28条

(3)显性  AA和aa、Aa 1:1

(4)转基因技术  基因控制生物的性状

(5)蚕丝为人类提供丝织品;蚕蛹可供食用;蚕是中外文化交流--丝绸之路的重要基础;蚕赋予诗人灵感,形成脍炙人口的诗篇等等(开放性试题,答案中体现政治、经济、文化、生活、艺术等方面合理内容即可得分)

单项选择题
单项选择题

On a weekday night this January, thousands of flag-waving youths packed Olaya Street, Riyadh’s main shopping strip, to cheer a memorable Saudi victory in the GCC Cup football final. One car, rock music blaring from its stereo, squealed to a stop, blocking an intersection. The passengers leapt out, clambered on to the roof and danced wildly in front of the honking crowd. Having paralyzed the traffic across half the city, they sped off before the police could catch them.

Such public occasion was once unthinkable in the rigid conformist kingdom, but now young people there and in other Gulf states are increasingly willing to challenge authority. That does not make them rebels: respect for elders, for religious duty and for maintaining family bonds remain pre-eminent values, and premarital sex is generally out of the question. Yet demography is beginning to put pressure on ultra-conservative norms.

After all, 60% of the Gulf’s native population is under the age of 25. With many more of its citizens in school than in the workforce, the region faces at least a generation of rocketing demand for employment. In every single GCC country the native workforce will double by 2020. In Saudi Arabia it will grow from 3.3m now to over 8m. The task of managing this surge would be daunting enough for any society, but is particularly forbidding in this region, for several reasons.

The first is that the Gulf suffers from a lopsided labor structure. This goes back to the 1970s, when ballooning oil incomes allowed governments to import millions of foreign workers and to dispense cozy jobs to the locals. The result is a two-tier workforce, with outsiders working mostly in the private sector and natives monopolizing the state bureaucracy. Private firms are as productive as any. But within the government, claims one study, workers are worth only a quarter of what they get paid.

Similarly, in the education sector, 30 years spent keeping pace with soaring student numbers has taken a heavy toll on standards. The Saudi school system, for instance, today has to cope with 5m students, eight times more than in 1970. And many Gulf countries adapted their curricula from Egyptian models that are now thoroughly discredited. They continue to favor rote learning of "facts" intended to instill patriotism or religious values.

Even worse, the system as a whole discourages intellectual curiosity. It channels students into acquiring prestige degrees rather than gaining marketable skills. Of the 120, 000 graduates that Saudi universities produced between 1995 and 1999, only 10,000 had studied technical subjects such as architecture or engineering. They accounted for only 2% of the total number of Saudis entering the job market.

The word "lopsided" (Paragraph 4) most probably means()

A.Detrimental

B.Unappealing

C.Harmonious

D.Unbalanced