问题 选择题

生活在绿草地上的蝗虫体色多为绿色而不是褐色;而生活在草木稀疏地上的蝗虫,体色多为褐色而不是绿色.对这种现象的解释是(  )

A.人工选择的结果

B.过度繁殖的结果

C.适者生存的结果

D.蝗虫会飞的结果

答案

自然选择说认为,生物要在自然界中要生存下去,都要为争夺足够的食物和空间进行生存斗争,在生存斗争中,具有有利变异的个体容易生存下来并繁殖后代,同时将有利变异遗传给下一代,而具有不利变异的个体则容易被淘汰,这种在生存斗争中,适者生存、不适者被淘汰的过程叫做自然选择,生活在绿草地上的蝗虫体色多为绿色而不是褐色;而生活在草木稀疏地上的蝗虫,体色多为褐色而不是绿色,这就是适者生存、不适者被淘汰的结果.

故选:C

阅读理解

It’s a sure sign that summer is over and winter is on the way — leaves that were once deep green turn red, yellow and bright orange. It happens every autumn. But did you ever wonder why?

The leaves start changing color when the nights start getting longer and the temperature starts getting cooler. Some scientists think that as the number of daylight hours shrinks, the leaves stop making chlorophyll which makes plants green. The reason is that the process of making chlorophyll requires sunlight. But according to horticulture (园艺) educator Susan Rose from Colorado State University, it turns out leaves don’t really change color at all. “The fall colors are actually there all along,” she said. “But they are covered by the green chlorophyll. As the chlorophyll stops being produced, the other colors can shine through.”

The kind of color that the leaves are going to change to is determined by the plant’s genetic (基因的) background. In some places, the leaves start changing color in September — before autumn even officially begins. In other places, they don’t change until late October or even November. Some scientists say the leaves have been changing color later than usual in recent years. And they think global warming has something to do with that.

In one study, researchers found that the growing season in the Northern Hemisphere was nearly a week longer, on average, in 2008 than it was in 1982. And a professor from Harvard University found that the leaves, west of Boston, Massachusetts, are changing color about three days later than they used to. However, other scientists disagree with the global warming theory. Susan Rose said the leaves in her part of Colorado are changing “right on schedule.” But the leaves in other parts of that state are running a little late. “The lateness in the mountains may have something to do with the really warm late summer and early fall,” she said. “But I’m afraid that’s just a guess.”

小题1:According to Susan Rose, _____.

A.the fall colors are always in leaves

B.leaves make chlorophyll all the seasons

C.leaves’ changing color have nothing to with the weather

D.leaves begin changing color because they start making chlorophyll小题2:The underlined word “shrinks” in Paragraph 2 could best be replaced by _____.

A.reduces

B.increases

C.lasts

D.appears小题3:Scientists guess leaves change color later than usual probably as a result of _____.

A.genetic background

B.dry weather

C.global warming

D.low temperature小题4:The purpose of the last paragraph is to tell readers _____.

A.why leaves change color at fall

B.leaves change color at different time

C.the effects of the global warming on plants

D.different opinions on the lateness of leaves’ changing color

单项选择题