问题 选择题

关于生态系统的有关叙述,错误的一项是(  )

A.生态系统是一个开放的系统

B.生态系有自动调节能力,但是有限的

C.物质和能量通过食物链和食物网流动

D.生态系统多种多样、各自独立、互不影响

答案

A、各生态系统并不是密闭的,孤立的,而是开放的,相互联系在一起.不符合题意.

B、在生态系统中各种生物的种类和数量总是维持在相对稳定的状态,达到生态平衡,这说明生态系统具有一定的自动调节能力,但这种调节能力是有一定限度的,如果外界的干扰超过了这个限度,生态系统就会遭到破坏.不符合题意.

C、在一个生态系统中,往往有很多条食物链,它们彼此交错连接,形成了食物网.生态系统中的物质和能量就是沿着食物链和食物网流动的.不符合题意.

D、生物圈中的生态系统多种多样,它们之间并不是相互孤立的,而是相互联系在一起的,生物圈是一个统一的整体.符合题意.

故选:D

解答题
阅读理解

阅读理解。

     What would you think if I told you I could eat 40 percent more food than other peopleeating boxes

of ice cream,bowls of noodles and plates of meatall while losing weight?

     You might hate me,thinking I have one of those annoyingly good metabolisms (新陈代谢) that just

burn up fat the instant it enters my body.You might wonder if I have an intestinal (肠的) worm,or perhaps an eating disorder.Or maybe you'd just shrug your shoulders and figure I have a rich fantasy life.You'd be

wrong.

     For my body to finish such a surprising task,I would have to be a mouse.Not just any mouse,but one

lucky enough to be involved in a new study at Baylor College of Medicine in Houston.

     After identifying an enzyme (酶) that allows fat to be stored in the body,scientists fed mice without

those enzymes,and found those mice were able to consume far more food than other miceand still weigh

10 to 15percent less.  

     Best of all,the mice that had no enzymes were in very good health,producing baby mice with no

problem and generally acting like any other mouse.That's great news for obesity researchers,who think

that scientists may figure out a way to prevent the fatmetabolizing (脂肪代谢) enzyme in humans and

control weight

gain.And such a pill would be very exciting for many struggling to get rid of dangerous extra pounds.

     But don't start planning any big dinner just yet:At this point,of course,any pill for humans is but a

twinkle (闪烁) in the eye of every medicine company's CEO.More tests are to be made,and eventually

humans will be introduced in the test.

     But for now,unfortunately,control in diet is still key.

1.What does "such a surprising task" in Paragraph 3 refer to?

A.Eating a lot of food while losing weight.  

B.Burning fat very quickly.

C.Controlling the diet.                  

D.Having a rich fantasy life.

2.Why did the author say he/she had to be a mouse in Paragraph 4?

A.Because a mouse can lose weight no matter how much it eats.

B.Because the weightlosing tests were made on the mouse.

C.Because the mouse has a very good metabolism.

D.Because the author wants to try the food without the enzyme.

3.What does the author want to show through the last two paragraphs?

A.You can be free of guilt when having big dinners.

B.Scientists cannot find the key to identifying the enzyme.

C .Don't overeat before the test is made on humans.

D.It is unnecessary to control weight at present.