北美托福机经英文版原文(2)

摘要:北美托福机经英文版原文(2)

1. 美国产业发展阶段灰蛾子和黑蛾子总数的调整。



关键见解是:环境污染比较严重使花草树木发黑,这时黑蛾子隐敝实际效果变好;另一方面,灰蛾子被吃得多。这一基础理论牵涉到一个生物学家的试验及其材料获得,学界有关这一還是有异议的,因此作者施展秘密武器:1966年美国根据除此之外,环保法桉之后,灰蛾子的总数又上去了,因此生物学家的基础理论就从反向获得确认。

辞�√猓�detecting。

How did peppered moths change because of the Industrial Revolution?

The Industrial Revolution caused pepper moths to adapt to a darker color because of the soot and ash everywhere so that they could hide from predators better,which made the black to gray moth ratio pull towards black. After the Industrial Revolution was over however then the black peppered moths numbers started to decrease and the grayish peppered moths number began to increase. This is evidence of adaptation.

The English moth, Biston betularia, is a frequently cited example of observed evolution. In this moth there are two color morphs, light and dark (typica and carbonaria). H. Kettlewell found that dark moths constituted less than 2% of the population prior to 1848. Then, the frequency of the dark morph began to increase. By 1898, the 95% of the moths in Manchester and other highly industrialized areas were of the dark type, their frequency was less in rural areas. The moth population changed from mostly light colored moths to mostly dark colored moths. The moths' color was primarily determined by a single gene. So, the change in frequency of dark colored moths represented a change in the gene pool. This change was, by definition, evolution.

The increase in relative abundance of the dark type was due to natural selection. The late eighteen hundreds was the time of England 's industrial revolution. Soot from factories darkened the birch trees the moths landed on. Against a sooty background, birds could see the lighter colored moths better and ate more of them. As a result, more dark moths survived until reproductive age and left offspring. The greater number of offspring left by dark moths is what caused their increase in frequency. This is an example of natural selection.

Populations evolve, not individuals. In order to understand evolution, it is necessary to view populations as a collection of individuals, each harboring a different set of traits. A single organism is never typical of an entire population unless there is no variation within that population. Individual organisms do not evolve, they retain the same genes throughout their life. When a population is evolving, the ratio of different genetic types is changing -- each individual organism within a population does not change. For example, in the previous example, the frequency of black moths increased; the moths did not turn from light to gray to dark in concert.

2. 微生物多样性

从地球赤道到北极,微生物的多样性逐渐变弱。里边提到深海里的比照不明显,由于温度差仅仅在上面几十米,下边全是一个样的黑和冷,因此作者觉得,深海多样性并不是由阳光照射和温度造成的。此外一个难题是多食动物generalist和专食动物specialist的差别。作者是根据时节�L期性转变,产生食材供给量的转变,随后食材的限定导致二种动物的不一样这一层面来谈。

3. 文艺复兴时期同业公会规章制度guild

先讲大师master的成名全过程,随后是全部行会的唯一性。然后是行会和城帮政府如何由前提条件互相支持(垄断)。之后政府看好垄断的大�I包因此参与进去分一杯羹。

除开政府之外,另一个行会的强悍敌人是城边不会受到法律法规管束,并且有着廉价劳动力(民工)的个人公司。之后行会市场竞争但是-由于成本费拼不过,价钱自然也拼不过。另外又碰到一些供货上的艰难,因此結果如何就…。也有,他们自己自身也是有分歧,主要是master中一些很有欲望,要想扩大,简易说便是内外交困。

雅思考试托福备考toefl共享托福机经




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