题干

对群落演替的理解不正确的是(      )

A:群落是一个动态系统,是不断发展变化的

B:裸岩上演替的草本植物阶段,也有乔木的种子迁入,但不适合生长

C:群落演替的本质是生物和环境相互作用共同演变的过程

D:人工群落组建后,它的物种丰富度不再变化

上一题 下一题 0.0难度 选择题 更新时间:2017-06-28 11:13:53

答案(点此获取答案解析)

D

同类题2

阅读下文,回答问题

小名

    大约我的出生与水有关,于是颇懂斯文的外公顺口给我起名叫淼儿。在“淼儿、淼儿”的呼唤中我慢慢长大了,到了要上学的年龄时,爸爸觉得该有个体面的学名才对,便为我取了个挺大众化的名字,可家里人还是“淼儿、淼儿”地叫。特别是妈妈叫得尤为响亮频繁。

    不知为什么,随着年龄的增长,再听到家人唤我小名竟有些不舒服了,好像有一种不被尊重的感觉。终于有一天,我在听到妈妈又一声“淼儿”的呼唤后,郑重地对她说:“妈妈,我有大名的。别叫我小名好吗?”然后,在妈妈惊愕的表情里,我走进了自己的房间。

    但妈妈终究还是改不了。

    那天是我16岁生日聚会,好多同学朋友都跑来了,家里的小客厅里挤得满满的。我一边给大家分发糖果,一边忙不迭地说着谢谢。爸爸妈妈在厨房里忙着做菜,当一碟碟香气四溢的精美小菜端上餐桌时,同学萍将送给我的大蛋糕端了上来。我立刻连声称谢着,打开了蛋糕盒,喊道:“妈妈,拿刀子来!”

    妈妈一边递过来一把瓜刀,一边叮咛:“淼儿,小心点!”

    “咦!你原来叫淼儿呀,挺好玩的名字!”

    萍欢快地叫着,同时在空中打了一个别致的手势。朋友们也善意地哄笑起来,我的脸“唰”地红到了耳根。

    晚上,临睡觉时,我推开了妈妈的房门。倚着门框,又一次对她说:“妈妈,我不是说过嘛,别叫我小名!”语气里已有了几分不耐。由此妈妈的脸上呈现了一种复杂的表情,看了走进来的爸爸一眼,叹了口气:“对不起!高翔。”可我听出我的名字在她口中却变得十分生硬,似乎很绕口。

    没多久,我要离开家到数百里外的一座城市去读书。

    不知怎的,妈妈竟在短短几天内学会了很有味地叫我的大名,而且同以前叫我小名时那样顺口熟练。我自然很高兴。

    分别的那一天,爸妈一齐送我去车站,爸爸一直喋喋地叮三嘱四,妈则沉默着,显得有些黯然神伤。我大人似的笑笑,反过来抚慰他们:“放心吧,没事的,我已不是孩子了。”

    火车开动的刹那,我从车窗探出头去,同他们挥手告别。一直不言不语的妈妈突然抬起了头,眼里竟有了泪。她紧跑着,挥动起双手,脱口喊了出来——

    “写信回来,淼儿!”

    我稍稍一愣,心里似乎被什么东西猛撞了一下,泪水夺眶而出。

(原文有改动)

同类题4

阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

    Many facts suggest that children are overweight (超重的) and the situation is getting worse, according to the doctors. I feel there are a number of reasons for this.

    Some people blame the fact that we are surrounded by shops selling unhealthy, fatty foods, such as fried chicken and ice cream, at low prices. This has turned out a whole generation of grown-ups who seldom cook a meal for themselves. If there were fewer of these restaurants, then probably children would buy less take-away food.

    There is another argument that blames parents for allowing their children to become overweight. I agree with this, because good eating habits begin early in life, long before children start to visit fast food shops. If children are given fried chicken and chocolate rather than healthy food, or are always allowed to choose what they eat, they will go for sweet and salty foods every time, and this will carry on throughout their lives.

    There is a third reason for this situation. Children these days take very little exercise. They do not walk to school. When they get home, they sit in front of the television or their computers and play computer games. Not only is this an unhealthy pastime (消遣), it also gives them time to eat more unhealthy food. What they need is to go outside and play active games or sports.

    The above are the main reasons for this problem, and therefore we have to encourage young people to be more active, as well as steering them away from fast food shops and bad eating habits.