Official 34 Set 5

纠错
  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
置顶

Plants and Pollinators

纠错
  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
What is the lecture mainly about?
  • A. The effect of agriculture on pollinators

  • B. Threats to the pollination cycle in tropical rain forests

  • C. The relationship between plants and their pollinators

  • D. Various plant species in tropical rain forests that attract pollinators

显示答案 正确答案: C

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    NARRATOR:Listen to part of a lecture in a botany class.

    FEMALE PROFESSOR:When we talk about pollination ecology, we’re talking about the relationship between a plant and its pollinator.From the plant’s perspective, the ideal pollinator is an animal that is underfed, ready to eat, and in a hurry.The pollinator, on the other hand, wants to remain well fed with as little effort as possible.These factors help drive the evolution of plants and their pollinators, both of which depend on this balanced and delicate relationship.Sometimes, only certain insects or birds can pollinate certain plant species.So to really understand pollination ecology, both the flower and its pollinators must be studied.

    Let's start with flowers.There are several important factors associated with pollination [slowly]: when and how often a plant flowers, how long the flowering cycle lasts, and the number of flowers that open at the same time.For example, flowering may coincide with the migration of a certain animal species that pollinates the plant. Or, producing many flowers at once may increase the number of pollinators a plant attracts.

    Other characteristics of flowers are also important.Features such as color, scent, and shape attract pollinators, as does the reward in the flower-the pollen or the nectar- that feeds the pollinator.For example, flowers that attract bats tend to be green or cream colored, because visibility isn’t important…bats are practically blind, remember… and these flowers bloom at night, when bats are active.

    Now, there’s a flower in the Amazon rain forest called a royal water lily, and the characteristics of its flowers change during the pollination process.The royal water lily uses color, temperature, and scent to attract the beetles that pollinate it.When the flowers of the royal water lily first open up, when they first bloom, they're white.They also emit a strong odor, and their temperature rises.Uh, producing heat serves two purposes: it magnifies the scent of the flower and it helps the beetles maintain their body temperature.When a beetle arrives at the flower, the flower closes around it for about 24 hours so that the beetle becomes covered with pollen.Then, when the flower opens, its color changes to red, and it cools down.When the beetle flies out, it carries the pollen to a different heated, white, fragrant flower.

    As you can see, plants go to a lot of trouble to attract attention.So what kind of attention are they attracting, and why?Well, sometimes flowers provide shelter for insects... a place to lay eggs, for instance.But usually the attraction is food... nectar and pollen.Nectar is mainly a sugar solution, while pollen is a grain made up of part of the plant-cell structure.In both nectar and pollen production, quality and quantity vary over time, but they’re always related to the needs of the pollinator.

    You can see that the relationships between pollinators and plants are delicate, so any number of factors can disturb them.Uh, human development is one, and agriculture is generally believed to be the most harmful.It can fragment habitats in a variety of ways, reducing the number of pollinators, which in turn may reduce the number or size of the flowers, which of course affects the animals that feed on them.Uh, exotic plant species, not native to the area, can move in and compete… even bees brought in to pollinate crops can alter natural pollen-dispersal systems of rain-forest plants.On the other hand, recent studies have shown that the disruption of one aspect of the pollination cycle doesn't usually lead to the extinction of other species...it turns out that plant-pollinator relationships are more adaptable to change than we thought.So really it’s hard to know just how agriculture affects the pollination of plants.

  • 旁白:听一段植物学课程。

    教授:当我们提到授粉生态学,我们谈论的是植物和传粉者之间的关系。从植物的角度来说,理想的传粉者是一种饥饿的动物,准备好饱餐一顿,而且时间不多。而另一方面,传粉者希望维持在费尽可能少的力气吃饱的状态。这些因素有助于推动植物和传粉者的进化,两者都取决于这种平衡且微妙的关系。有时候,只有某些昆虫或鸟类才能给某些植物传粉。要想真正了解授粉生物学,花朵和传粉者都要研究,缺一不可。

    我们先讲花。和传粉息息相关的重要因素有好几个:植物开花的时间和频率、花期有多长、同时开花的花朵数量。举个例子,植物开花可能正好赶在某种为之传粉的动物迁徙的时候,或者,一次性开很多朵花也可能会吸引到更多的传粉者。

    花朵的其它特性也很重要。例如像是颜色、香味和形状等能吸引传粉者的特质,还有藏在花朵里的奖励,花粉或花蜜,给传粉者提供食物。譬如,吸引蝙蝠的花朵通常是绿色或奶油色的,因为可见度并不重要。记住,蝙蝠基本上是瞎的,这些花在晚上盛开,这时候蝙蝠很活跃。

    在亚马逊森林有一种花叫王莲,它的花朵特性在传粉期间会发生改变。王莲以颜色、温度和香味来吸引甲虫为之传粉。当王莲的花苞打开时,当王莲最初开花时,花是白色的。花朵还会散发出强烈的气味,温度也会上升。制造热量有两个目的:它(制造热量)能把花朵香气变得更浓烈,也有助于甲虫维持体温。当一只甲虫落到花朵上时,该花朵会闭合24小时,就能让甲虫身上覆满花粉了。接着当花朵打开时,颜色就会变为红色,温度下降。甲虫飞出来时,它会把花粉带到另一朵温度较高的、白色的芬芳的花朵上去。

    正如你所见,植物花费不少精力来吸引(传粉者)注意。那么,它们想吸引什么注意呢?为什么?有些时候花朵给昆虫提供庇护,比如为它们产卵提供场所。但通常来说,食物才是吸引力所在:花蜜和花粉。花蜜主要是糖溶液,花粉则是由部分植物细胞结构组成的颗粒物。在制造花蜜和花粉的过程中,质量和数量随着时间变化而不同,但它们都和传粉者的需求有关。

    你们也能发现,传粉者和植物之间的关系是很微妙的,任意因素都能影响它们。人类发展就是其一,而农业被认为是其中最有害的。农业会以不同方式将栖息地碎片化,减少了传粉者的数量,转而可能会减少花朵数量或让花朵变小,这肯定也会影响以此为食的动物。外来植物,即不是本区域的原生植物,能迁进来,参与竞争,甚至连引进来的蜜蜂给作物传粉,也会改变雨林植物的花粉分布系统。另一方面,最近研究表明,仅干扰授粉循环的其中一方面,通常不会导致其它物种的灭绝,原来植物和传粉者的关系比我们预想中的更具适应性。所以,人们真的很难知道到底农业是怎样影响植物传粉的。

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  • 本题对应音频:
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    音频1
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    题型分类:主旨题

    原文定位:

    When we talk about pollination ecology, we’re talking about the relationship between a plant and its pollinator. From the plant’s perspective, the ideal pollinator is an animal that is underfed, ready to eat, and in a hurry. The pollinator, on the other hand, wants to remain well fed with as little effort as possible. These factors help drive the evolution of plants and their pollinators, both of which depend on this balanced and delicate relationship. Sometimes, only certain insects or birds can pollinate certain plant species. So to really understand pollination ecology, both the flower and its pollinators must be studied.

    选项分析:

    文章刚开始教授就说we are talking about植物和它的传粉者的关系。后面具体给出几句解释,又再次总结,那么为了明白授粉生态学,双方都必须研究。之后就都在说两者关系了。对应C选项。

    其他项不是主要论述内容

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