2014年托福阅读真题+题目+答案解析：Wind Pollination

2014年托福阅读真题+题目+答案解析：Wind Pollination

 Pollen, a powdery substance, which is produced by flowering plants and contains male reproductive cells, is usually carried from plant to plant by insects or birds, but some plants rely on the wind to carry their pollen. Wind pollination is often seen as being primitive and wasteful in costly pollen and yet it is surprisingly common, especially in higher latitudes. Wind is very good at moving pollen a long way; pollen can be blown for hundreds of kilometers, and only birds can get pollen anywhere near as far. The drawback is that wind is obviously unspecific as to where it takes the pollen. It is like trying to get a letter to a friend at the other end of the village by climbing onto the roof and throwing an armful of letters into the air and hoping that one will end up in the friend's garden. For the relatively few dominant tree species that make up temperate forests, where there are many individuals of the same species within pollen range, this is quite a safe gamble. If a number of people in the village were throwing letters off roofs, your friend would be bound to get one. By contrast, in the tropics, where each tree species has few, widely scattered individuals, the chance of wind blowing pollen to another individual is sufficiently slim that animals are a safer bet as transporters of pollen. Even tall trees in the tropics are usually not wind pollinated despite being in windy conditions. In a similar way, trees in temperate forests that are insect pollinated tend to grow as solitary, widely spread individuals.

Since wind-pollinated flowers have no need to attract insects or other animals, they have dispensed with bright petals, nectar, and scent. These are at best a waste and at worst an impediment to the transfer of pollen in the air. The result is insignificant-looking flowers and catkins (dense cylindrical clusters of small, petalless flowers).

Wind pollination does, of course, require a lot of pollen. Birch and hazel trees can produce 5.5 and 4 million grains per catkin, respectively. There are various adaptations to help as much of the pollen go as far as possible. Most deciduous wind-pollinated trees (which shed their leaves every fall) produce their pollen in the spring while the branches are bare of leaves to reduce the surrounding surfaces that “compete" with the stigmas (the part of the flower that receives the pollen) for pollen. Evergreen conifers, which do not shed their leaves, have less to gain from spring flowering, and, indeed, some flower in the autumn or winter.

Pollen produced higher in the top branches is likely to go farther: it is windier (and gustier) and the pollen can be blown farther before hitting the ground. Moreover, dangling catkins like hazel hold the pollen in until the wind is strong enough to bend them, ensuring that pollen is only shed into the air when the wind is blowing hard. Weather is also important. Pollen is shed primarily when the air is dry to prevent too much sticking to wet surfaces or being knocked out of the air by rain. Despite these adaptations, much of the pollen fails to leave the top branches, and only between 0.5 percent and 40 percent gets more than 100 meters away from the parent. But once this far, significant quantities can go a kilometer or more. Indeed, pollen can travel many thousands of kilometers at high altitudes. Since all this pollen is floating around in the air, it is no wonder that wind-pollinated trees are a major source of allergies.

Once the pollen has been snatched by the wind, the fate of the pollen is obviously up to the vagaries of the wind, but not everything is left to chance. Windborne pollen is dry, rounded, smooth, and generally smaller than that of insect-pollinated plants. But size is a two-edged sword. Small grains may be blown farther but they are also more prone to be whisked past the waiting stigma because smaller particles tend to stay trapped in the fast-moving air that flows around the stigma. But stigmas create turbulence, which slows the air speed around them and may help pollen stick to them.

paragraph 1

1. The word "drawback" in the passage is closest in meaning to

A other side of the issue

B objection

C concern

D problem

答案：D

解析：【判定题型】：题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。 【关键词定位】：根据关键词“drawback”,定位到原句“xxxxxxxxxxxxxx”。 【词汇解析】：词汇“drawback”的意思是“缺点，不利条件”,带入到原句中，原句的意思是“xxxxxxxxxxxxxxx”。 【选项分析】 A：事情的另外一方面。不符，错误 B：异议，反对。不符，错误 C：关心，关注。不符，错误 D：问题，难题与 drawback 在这里的含义相符，故为正确答案。

2. Which of the following can be inferred from paragraph 1 about pollen production?

A Pollen production requires a significant investment of energy and resources on the part of the plant.

B The capacity to produce pollen in large quantities is a recent development in the evolutionary history of plants.

C Plants in the tropics generally produce more pollen than those in temperate zones.

D The highest levels of pollen production are found in plants that depend on insects or birds to carry their pollen.

答案：A

【判定题型】：根据题干中出现的关键词“imply”/“infer”/“suggest”等其他表示推断的词，判定本题为推理题。 【关键词定位】直接定位到第1段。 【逻辑分析】第1段介绍了风媒传粉，也介绍了其优点和缺点。 【选项分析】 A：根据原文的 wind is good at moving pollen a long way 可以推断 pollen production 是需要 energy 的，根据 Pollen,…. is usually carried from plant to plant…可知，pollen production 是需要 resource 的。故 A 选项正确。 B：B 选项的说法无中生有。错误 C：C 选项的比较关系在原文无法得出。 错误 D：D 选项对 highest levels of pollen production 的传播方式的说法也是无中生有的。错误

3. According to paragraph 1, wind-pollinated trees are most likely to be found

A in temperate forests

B at lower latitudes

C in the tropics

D surrounded by trees of many different species

3.答案：A

【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。 【关键词定位】：根据关键词“wind-pollinated trees”,定位到 Passage 1 第5句，原句为 For the relatively few dominant tree species that make up temperate forests, where there are many individuals of the same species within pollen range, this is quite a safe gamble.”，意思是“对于组成温带森林的优势树种相对较少，在花粉范围内有许多相同树种的个体，这是一个相当安全的赌博。”。 【逻辑分析】根据原文的 For the relatively few… temperate forests… this is quite a safe gamble.此句中的 this 根据前文可知就是”风传播“，所以 wind-pollinated trees 很有可能会在 temperate forests 里发现。 【选项分析】 A：符合文意，正确 B：不符，错误 C：不符，错误 D：不符，错误

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