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问题 问答题 简答题

生物反应与一般化学反应的显著区别

答案

参考答案：

（1）生物反应存在着活细胞，在反应中可以将它看着催化剂

（2）由于细胞是生长着的，它对营养有一定的要求，使得参与反应的成分很多

（3）生物反应的途径通常不是单一的，反应过程也往往伴随着生成代谢产物的反应，它受到众多环境因素的影响

问答题

（1）有两个做匀加速直线运动的质点，下列说法正确的是______（填正确答案标号）

A．相同时间里，速度大的质点加速度必定大

B．相同时间里，若加速度相同，初速度大的质点的末速度一定大

C．相同时间里，加速度大的质点速度变化必定大

D．相同时间里，末速度越大的质点，通过的位移一定越大

E．相同时间里，平均速度大的质点，通过的位移一定越大

（2）一辆汽车在平直公路上从A站开往B站，在开始的

1
5
位移上平均速度为v，在以后的
4
5
位移上平均速度为2v，这辆汽车全程的平均速度是多少？
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单项选择题

Should we care if over 150 known species of animals have (91) from the earth in the last fifty years Should we be concerned that there are (92) thousands of species whose very existence is (93) endangered—largely because of our activities (94) , after all, is the natural end of populations. Species are born, then (95) , and then die. Some live a (96) time, perhaps millions of years; some die more quickly. We have (97) the extinction of many species we know about, and we have undoubtedly sealed the (98) of others. In fact, there are undoubtedly many other species that have lived among us during our time on earth, but that have disappeared as a (n) (99) of our activities without our ever having known they existed.
It is hard to explain the rationale of many of us who are concerned about such matters. I have never seen a sea whale, (100) I don’t want them to become extinct. Moreover, I felt this way long before I understood anything about how they might be an important part of an ecosystem. Possibly such feelings merely reflect the cultural attitude that it is "nice" to wish other living things well; thus, the attitude is (101) . I feel nice.
There are, of course, more rational reasons for (102) the extermination of any species. For one thing, the kind of attitude that encourages or sanctions the destruction of other species is a threat (103) our own wellbeing. If such an attitude exists, we ourselves might (104) victim to it. living things (including us) might be expected to fare better where there is (105) for life. The extinction of other species could also threaten us (106) by simplifying the system of which we are a part or by destroying parts of the ecosystem (107) which we directly rely. For example, if we continue to poison the oceans (108) we are willing to believe only a few bottom dwellers are affected, we might (109) overstep some critical threshold and trigger the wholesale death of plankton, thus finding ourselves without a major (110) of the world’s food and with our oxygen supplies dwindling.

A．seemingly

B．indirectly

C．certainly

D．conveniently
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