托福閱讀對27個多少分

托福閱讀對27個多少分?下面就來跟著小編一起來看精彩內容吧，最后希望同學們都能戰勝托福中的重重難關，沖向終點，更多精彩內容盡在學習啦，預祝考生取得理想成績!

托福閱讀對27個多少分

關于托福閱讀錯幾個得多少分的問題，大家可以參考托福閱讀計分方法：

1、托福三篇文章(如遇加試時從五篇中隨機選三篇)計分，每篇12-14道題。

2、三篇文章回答正確的題目數量加起來就能得出托福閱讀總分。

3、除重要歸類題和觀點題以外，每道題的分值都是1分。

4、重要觀點題的分值可能是2分。歸類題為3或4分。

5、考試所得分數范圍：0-30分。

托福閱讀TPO34原文第3篇:昆蟲保護植物

托福閱讀原文

Protection of Plants by Insects

【1】Many plants - one or more species of at least 68 different families - can secrete nectar even when they have no blossoms, because they bear extrafloral nectaries (structures that produce nectar) on stems, leaves, leaf stems, or other structures.These plants usually occur where ants are abundant, most in the tropics but some in temperate areas. Among those of northeastern North America are various plums, cherries, roses, hawthorns, poplars, and oaks. Like floral nectar, extrafloral nectar consists mainly of water with a high content of dissolved sugars and, in some plants, small amounts of amino acids. The extrafloral nectaries of some plants are known to attract ants and other insects, but the evolutionary history of most plants with these nectaries is unknown. Nevertheless, most ecologists believe that all extrafloral nectaries attract insects that will defend the plant.

【2】Ants are portably the most frequent and certainly the most persistent defenders of plants. Since the highly active worker ants require a great deal of energy, plants exploit this need by providing extrafloral nectar that supplies ants with abundant energy. To return this favor, ants guard the nectaries, driving away or killing intruding insects that might compete with ants for nectar. Many of these intruders are herbivorous and would eat the leaves of the plants.

【3】Biologists once thought that secretion of extrafloral nectar has some purely internal physiological function, and that ants provide no benefit whatsoever to the plants that secrete it. This view and the opposing “protectionist” hypothesis that ants defend plants had been disputed for over a hundred years when, in 1910, a skeptical William Morton Wheeler commented on the controversy. He called for proof of the protectionist view: that visitations of the ants confer protection on the plants and that in the absence of the insects a much greater number would perish or fail to produce flowers or seeds than when the insects are present. That we now have an abundance of the proof that was called for was established when Barbara Bentley reviewed the relevant evidence in 1977, and since then many more observations and experiments have provided still further proof that ants benefit plants.

【4】One example shows how ants attracted to extrafloral nectaries protect morning glories against attacking insects. The principal insect enemies of the North American morning glory feed mainly on its flowers or fruits rather than its leaves. Grasshoppers feeding on flowers indirectly block pollination and the production of seeds by destroying the corolla or the stigma, which receives the pollen grains and on which the pollen germinates. Without their colorful corolla, flowers do not attract pollinators and are not fertilized. An adult grasshopper can consume a large corolla, about 2.5 inches long, in an hour. Caterpillars and seed beetles affect seed production directly. Caterpillars devour the ovaries, where the seeds are produced, and seed beetle larvae eat seeds as they burrow in developing fruits.

【5】Extrafloral nectaries at the base of each sepal attract several kinds of insects, but 96 percent of them are ants, several different species of them. When buds are still small, less than a quarter of an inch long, the sepal nectaries are already present and producing nectar. They continue to do so as the flower develops and while the fruit matures. Observations leave little doubt that ants protect morning glory flowers and fruits from the combined enemy force of grasshoppers, caterpillars, and seed beetles. Bentley compares the seed production of six plants that grew where there were no ants with that of seventeen plants that were occupied by ants. Unprotected plants bore only 45 seeds per plant, but plants occupied by ants bore 211 seeds per plant. Although ants are not big enough to kill or seriously injure grasshoppers, they drive them away by nipping at their feet. Seed beetles are more vulnerable because they are much smaller than grasshoppers. The ants prey on the adult beetles, disturb females asthey lay their eggs on developing fruits, and eat many of the eggs they do manage to lay

托福閱讀TPO34試題第3篇:昆蟲保護植物

1.According to paragraph 1，floral nectar and extrafloral nectar are alike in that

A.they are likely to be produced by the same plants.

B.they basically consist of the same chemical components.

C.they attract only insects that will defend the plant.

D.they are produced by the same parts of the plant.

2.To say that ants are "persistent" defenders of plants means that

A.they defend plants against a wide variety of threats.

B.they continue to defend plants for as long as the plants are threatened.

C.they are successful defenders of plants.

D.they are easily observable defenders of plants.

3.What can be inferred from paragraph 2 about the ants that are attracted to the extrafloral nectaries?

A.They do not eat the leaves of the plants that produce extrafloral nectar.

B.They live almost entirely on extrafloral nectar.

C.They spend most of their energy guarding extrafloral nectaries.

D.They frequently fight among themselves over extrafloral nectar.

4.According to paragraph 3, what was the position of the opponents of the "protectionist" hypothesis?

A.Extrafloral nectar provides plants with a direct defense against attack by insects.

B.Ants substantially benefit plants that secrete extrafloral nectar.

C.The secretion of extrafloral nectar plays a role in the plant’s internal functioning.

D.Ants visit plants that secrete extrafloral nectar as often as they visit plants that do not.

5.The word "skeptical" in the passage is closest in meaning to

A.curious.

B.doubtful.

C.open-minded.

D.practical.

6.Which of the sentences below best expresses the essential information jn the highlighted sentence in the passage Incorrect choices change the meaning in important ways or leave out essential information.

A.We now have ample proof that ants benefit plants.

B.Barbara Bentley has called for additional proof that ants benefit plants.

C.In 1977 Barbara Bentley conducted research that proved that all prior studies were wrong.

D.Proof that ants benefit plants will require many more observations and experiments.

7.According to paragraph 4, what effect does the destruction of the corolla have on plants.

A.It leaves the seeds exposed and unprotected.

B.It prevents the stigma from developing.

C.It keeps pollen grains from attaching properly.

D.It prevents the flower from attracting pollinators.

8.The word "devour" in the passage is closest in meaning to

A.attack.

B.eat.

C.damage.

D.prefer.

9.What role does paragraph 5 play in the passage?

A.It offers various kinds of evidence for the protectionist view.

B.It presents the study that first proved that ants benefit plants.

C.It explains how insects find sources of nectar.

D.It presents information that partly contradicts the protectionist view.

10.The word "vulnerable" in the passage is closest in meaning to

A.numerous.

B.harmful.

C.open to attack.

D.difficult to locate.

11.According to paragraph 5, what did Bentley’s comparative study show?

A.Many more plants grew in places where ants were present than where they were absent.

B.The ants preferred plants with low seed production to plants with high seed production.

C.The plants occupied by ants produced many more seeds than those that were not occupied by ants.

D.The plants that grew in places without ants were much smaller and weaker than those that grew in places where ants were present.

12.According to paragraph 5, ants defend morning glory plants from seed beetles in each of the following ways EXCEPT:

A.driving adult beetles off the plants by nipping at their feet.

B.catching and eating adult beetles.

C.eating beetle eggs they find on developing fruits.

D.making it difficult for beetles to lay eggs on developing fruits.

13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit? Sometimes they capture the insects to feed their protein-hungry larvae.

Ants are portably the most frequent and certainly the most persistent defenders of plants. ■【A】 Since the highly active worker ants require a great deal of energy, plants exploit this need by providing extrafloral nectar that supplies ants with abundant energy. ■【B】 To return this favor, ants guard the nectaries, driving away or killing intruding insects that might compete with ants for nectar. ■【C】 Many of these intruders are herbivorous and would eat the leaves of the plants. ■【D】

14. Directions: An introductory sentence for a brief summary of the passage of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This questions is worth 2 points.

Many plants have extrafloral nectaries that produce nectar even during periods in which the plant is not flowering.

A.Evolutionary history shows that plants that produce extrafloral nectar originated in the tropics.

B.Extrafloral nectar has a higher concentration of sugar than floral nectar and is more attractive to ants and other insects.

C.The protectionist hypothesis is that extrafloral nextar attracts ants, and that the ants, in order to preserve this energy-rich food source, attack insects that might harm the plant.

D.Evidence accumulated during the twentieth century proved that ants provide significant benefits for plants with extrafloral nectaries.

E.Research has shown that American morning glory plants that are protected by ants produce significantly more seeds than morning glory plants that are not protected by ants.

F.Ants generally ignore small insects, but they will eat the adults of large insect species as well as their eggs and larvae.

托福閱讀TPO34第3篇:昆蟲保護植物參考答案

1.B

2.B

3.A

4.D

5.A

6.A

7.C

8.B

9.B

10.C

11.C

12.A

13.C

14.CDE

托福閱讀對27個多少分相關文章：

★ 托福閱讀沒到27分的原因分析

★ 托福寫作20到27分,我是這樣提分的

★ 托福聽力16-27分,我是這么做的

★ 2018年1月27日托福真題回憶