反馈建议 切换旧版 去做题 结束训练
全文精听 逐句精听
句间停顿： 关
  • 关
  • 1S
  • 3S
  • 5S
语速： x 1.0
  • 速度0.8X
  • 速度1.0X
  • 速度1.2X
  • 速度1.5X
  • 速度1.8X
  • 速度2X
始终显示原文
欢迎使用 KMF 精听精研
坚持练习精听，反复听、吃透每个句子，能够快速 提升听力能力
开始精听
或按 「 空格」开始播放

段落1

Listen to part of a lecture in a biology class.

点击显示原文

隐藏原文=

OK so far we've been studying interactions of populations in nature that belong to a category of negative, um, we've discussed predators that feed on the prey, like wolf and rabbit, corn root worms that feed on the corn and so forth.

点击显示原文

隐藏原文=

This type of relationship is characterized by the fact that one organism actually harms the other.

点击显示原文

隐藏原文=

Today, I wanna begin talking about some positive interactions.

点击显示原文

隐藏原文=

First of all, let's look at mutualism and the classic mutualistic relationship.

点击显示原文

隐藏原文=

A mutually stick relationship is when two organisms of different species work together, each benefiting from the relationship and do not harm each other.

点击显示原文

隐藏原文=

Some mutualisms are so close that interacting species actually can't survive without each other.

点击显示原文

隐藏原文=

One good example of this is the mutualistic relationship between the yucca plant and yucca moth, which you read about in your textbook for today.

点击显示原文

隐藏原文=

Tom, why is it that the yucca plant can't live without the yucca moth?

点击显示原文

隐藏原文=

S: Well It needs the yucca moth as a pollinate a right?

点击显示原文

隐藏原文=

Um The yucca moth collects and carries the pollen from one flower to another. In different areas. The yucca plant will produce seeds that get carried off by the wind and eventually germinate and grow into new plants again.

点击显示原文

隐藏原文=

Great. And Interestingly, only the yucca moth can pollinate the yucca plant.

点击显示原文

隐藏原文=

Most people think of bees when they talk about a pollinater but even bees can't pollinate the yucca plant because they can't move the yucca pollen.

点击显示原文

隐藏原文=

Yucca pollen is really heavy and sticky, so it can't be scattered by wind or by casual contact with other insects.

点击显示原文

隐藏原文=

But the yucca moth has special mouth parts that enable it to carry the pollen.

点击显示原文

隐藏原文=

Uh Jennifer, why can't the yucca moth live without the yucca plant?

点击显示原文

隐藏原文=

S: Well what the female yucca moth does is, um, when she pollinates the yucca plant, she also lays her eggs.

点击显示原文

隐藏原文=

And then when the eggs hatch, the larvae feed on the yucca plant seeds.

点击显示原文

隐藏原文=

They can't eat any other kind of food. I mean they will die from hunger unless they eat the yucca seeds.

点击显示原文

隐藏原文=

Very good. So this is the perfect kind of relationship.

点击显示原文

隐藏原文=

The yucca moth pollinates the yucca plant. The younger plants make seeds, and in return, the yucca moth gets food for its young from the yucca plant.

点击显示原文

隐藏原文=

S: Excuse me, professor. Um I seem to be missing something here.

点击显示原文

隐藏原文=

I mean, I thought you said in mutualism, neither species is harmed.

点击显示原文

隐藏原文=

But the yucca moth larvae eat the yucca plant seeds. Doesn't that mean the yucca moth actually harms the yucca plant?

点击显示原文

隐藏原文=

That's a good question, Tom. Actually, it's not that much of a problem, because there are plenty of seeds for the larvae to eat without harming the yucca plant supply.

点击显示原文

隐藏原文=

Also, the yucca moth doesn't lay too many eggs. On one flower, she usually lays about one to three per flower.

点击显示原文

隐藏原文=

So most of the seeds will still be safe when the eggs hatch.

点击显示原文

隐藏原文=

But it raises an interesting question. What if a female yucca moth plays unfair? What if she plays an unfair game and lays more eggs on each chunk of flour than the usual one to three?

点击显示原文

隐藏原文=

The moth would certainly be benefited this way, because more offspring could be produced, but it wouldn't be very good for the plant.

点击显示原文

隐藏原文=

Well one scientist has observed that the yucca plant produces a huge array of flowers, and then drops a large number of flowers, including many that have been pollinated and have eggs on them.

点击显示原文

隐藏原文=

This dropping of flowers is a matter of pure chance.

点击显示原文

隐藏原文=

Uh You never know which flowers will fall off.

点击显示原文

隐藏原文=

So if the yucca moth lays lots of eggs at a few flowers, those eggs may all be dropped.

点击显示原文

隐藏原文=

And She may produce no young at all.

点击显示原文

隐藏原文=

But if the yucca moth lays fewer eggs on lots and lots of flowers, there's a greater chance that more caterpillars will hatch and survive. Among the flowers that have remained on the planned.

点击显示原文

隐藏原文=

According to the observation, perhaps the yucca plant is in a sense, forcing the moth to lay eggs thin and wide.

点击显示原文

隐藏原文=
[ < 空格 > ]
当前句 /
/
  • 段落1
  • 第 1 句
  • 第 2 句
  • 第 3 句
  • 第 4 句
  • 第 5 句
  • 第 6 句
  • 第 7 句
  • 第 8 句
  • 第 9 句
  • 第 10 句
  • 第 11 句
  • 第 12 句
  • 第 13 句
  • 第 14 句
  • 第 15 句
  • 第 16 句
  • 第 17 句
  • 第 18 句
  • 第 19 句
  • 第 20 句
  • 第 21 句
  • 第 22 句
  • 第 23 句
  • 第 24 句
  • 第 25 句
  • 第 26 句
  • 第 27 句
  • 第 28 句
  • 第 29 句
  • 第 30 句
  • 第 31 句
  • 第 32 句
  • 第 33 句
  • 第 34 句
  • 第 35 句
  • 第 36 句

+ 创建收藏夹
保存 取消