问题 选择题

打开你的影集你会发现,现在的你比小学的你长高了许多,你知道这是什么缘故么?(  )

A.细胞的分裂和生长

B.细胞数目的增多

C.细胞体积的增大

D.细胞的分化

答案

答案:A

题目分析: 生物体由小长大,是通过细胞的生长、分裂和分化长大的。构成生物体的细胞要从周围环境中吸收营养物质,并且转变成组成自身的物质,体积会由小变大,这就是细胞的生长;但细胞不能无限制的长大,一部分细胞长到一定的大小,就会进行分裂;细胞分裂就是一个细胞分裂成两个细胞,细胞分裂使细胞数目增多;

在个体发育过程中,一个或一种细胞通过分裂产生的后代,在形态、结构和生理功能上发生差异性的变化,形成了多种多样的细胞,这一过程叫做细胞的分化。细胞分化的结果是形成组织,使生物体形成不同层次。

考点: 细胞分裂和细胞分化的意义。

选择题
阅读理解

阅读理解。

     Some years ago industries had more freedom than they have now, and they did not need to be as careful

as they must today. They did not need to worry a lot about the safety of the new products that they developed.

They did not have to pay much attention to the health and safety of the people who worked for them. Often

new products were dangerous for the people who used them; often conditions in the work place had very bad

effects on the health of the workers.

     Of course sometimes there were real disasters which attracted the attention of governments and which

showed the need for changes. Also scientists who were doing research into the health of workers sometimes

produced information that governments could not ignore. At such times, there were inquiries into the causes

of the disasters or the problems. New safety rules were often introduced as a result of these inquiries; however,

the new rules came too late to protect the people who died or who became seriously ill.

     Today many governments have special departments that protect customers and workers. In the U.S., for

example, there is a department that tests new airplanes and gives warnings about possible problems. It also

makes the rules that aircraft producers must follow. Another department controls the foods and drugs that

companies sell. A third department looks at the places where people work, and then reports any companies that

are breaking the laws which protect the health and safety of workers. Of course, new government departments

and new laws cannot prevent every accident or illness, but they are having some good results. Our work places

are safer and cleaner than before. The planes and cars that we use for travel are better. Producers are thinking

more about the safety and health of the people who buy and use their products.

1. It can be inferred from the passage that in the past ____.

A. workers often got ill because of the poor working conditions

B. companies were free to put out any products they wanted to

C. many people were killed by dangerous products

D. industries were as careful in management as they are today

2. As can be seen in the passage ____.

A. governments and companies had different opinions about the safety of products

B. scientists also helped improve the safety and health of workers and customers

C. government officials often did not listen to scientists

D. governments paid no attention to the safety of products at all 

3. From the passage, we know that some years ago safety rules ____.

A. were put forward due to scientists' recommendations

B. came into being as a result of the workers' demands

C. were introduced because quite a number of people were killed or seriously injured

D. were effective enough to protect workers and customers

4. The special departments protect customers and workers in many ways EXCEPT by ____.

A. testing new products

B. designing new products

C. controlling the sale of products

D. inspecting work places