就是为了给出一个例子来说明这种不同寻常的指数增长并不会跟随着减少。正确答案：B 14.What point does the professor make when she discusses the carrying capacity of an ecosystem? A.The availability of food is more important for species than the availability of space.
B.The amount of environmental resistance in an ecosystem does not change over time. C.Environmental resistance controls the population size of species in an ecosystem. D.The population size of most species increases at a constant rate. 解析：(1’30’’)教授用BUT转折回到男生说的观点，But for most species, most of the time, resources are finite. There’s only so much available … which leads me to my point. Every ecosystem has what we call a carrying capacity. 教授开始阐述自己的观点，即生态环境的承载容量是会限制物种的最大数量的。(2’06’’)There are always factors that limit population growth. This is called environmental resistance. 这些限制因素就成为：环境抵抗因素。正确答案：C 15.How did the researchers test the links between acorns, white-footed mice, and gypsy moths in a forest? 解析：(3’48’’)男生对教授说的例子提出疑问：How can we know that for sure? It seems like a big jump from more acorns to fewer gypsy moths. 于是教授解释：We can know for sure because in this oak forest, the researchers decided to test the links between acorns and the two animal species. In some parts of the forest, they had volunteers drop a large number of extra acorns on the forest floor. And in another section of the forest, they remove a number of white-footed mice. 正确答案：D 16.What does the professor say can lead to a change in the gypsy moth population in a forest? (click on 2 answers) 解析：(4’13’’) In the forest areas where extra acorns had been dropped, the gypsy moth population soon went into a significant decline. But in the section of the forest where the white-footed
mice had been removed, the gypsy moth population exploded. 当橡子少了，舞毒蛾也会极大减少。但是当白脚鼠被移除，舞毒蛾数量会膨胀。也就是说，橡子和白脚鼠的数量变化会引发舞毒蛾的数量的变化。正确答案：BC
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- Spring '15
- d., B., c., Gypsy moth, Copper Basin