『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 10 Lec 3听力练习：What is the main purpose of the lecture?原文题目答案解析，TPO/Official 10 Lec 3听力原文范文音频翻译。

托福TPO/Official 10 Lec 3听力原文What is the main purpose of the lecture?-新东方托福官方网校手机版

旁白：听一段生态学的课堂讲解。

Narrator: Listen to part of a lecture in an Ecology Class.

教授：我们一直在讲养分，就是环境中对生物发展、健康生存并繁殖的必要因素。

Professor: So we’ve been talking about nutrients, the elements in the environment that are essential for living organisms to develop, live a healthy life and reproduce.

一些养分很稀少，环境中存在的真的是很少。

Some nutrients are quite scarce; there just isn’t much of them in the environment.

当养分在环境中反复被使用时，我们称之为养分循环。

When nutrients are used over and over in the environment, we call that a nutrient cycle.

由于养分的重要性和贫乏性，营养回收就变成整个生态系统过程中最重要的一步。

Because of the importance of nutrients and their scarcity, nutrient recycling is one of the most significant eco-system processes that we’ll cover in this course.

最重要的三种营养回收包括氮循环、碳循环以及今天我们要讲的磷循环。

The three most important nutrient cycles are the nitrogen cycle, the carbon cycle and the one we are going to talk about today, the Phosphorus cycle.

许多生态学家都研究了磷循环，因为正如我说的，磷循环是非常重要的养分并且也不是很充足。

So the Phosphorus cycle has been studied a lot by ecologists because like I said, Phosphorus is an important nutrient and it’s not so abundant.

最多的磷存在于海洋深处的岩石中。

The largest quantities are found in rocks and at the bottom of the ocean.

Well, let’s start with the Phosphorus in rocks.

The rocks get broken down into smaller and smaller particles as they are weathered.

岩石产生风化，并在风化过程中会变成越来越小的微粒。

They are weathered slowly by rain and wind over long periods of time.

磷在岩石分解过程中被释放出来，并渗透到泥土中。

Phosphorus is slowly released as the rocks are broken down and it gets spread around into the soil.

一旦磷融入泥土，就会被植物的根部所吸收。

Once it’s in the soil, plants absorb it through their roots.

学生：这就是人们开采包含磷的岩石来推助农业的原因吗？

Student: So that’s the reason people mine rocks that contain a lot of Phosphorus to help with the agriculture?

教授：呃，人们开采岩石，将其打碎，然后将提取出来的磷放在农业化肥里。

Professor: Uh-huh, they mine the rock, artificially break it down and put the Phosphorus into agricultural fertilizers.

所以说人类在磷循环中也起到了巨大的作用——即通过打碎岩石，将磷撒放在泥土中来增快自然过程。你们明白吧。

So humans can play a role in the first part of the Phosphorus cycle – the breaking down of rocks and the spreading of Phosphorus into the soil by speeding up the rate at which this natural process occurs. You see.

Now after the Phosphorus is in the soil, plants grow.

They use Phosphorus from the soil to grow.

那么磷就再次循环到泥土中，吃这些植物的动物、或是吃这些动物的其他动物也如此。

And the Phosphorus is recycled back into the soil; same thing with the animals that eat those plants, or eat other animals that have eaten those plants.

我们把这称之为陆地阶段的磷循环。

We call all of this – the land phase of the Phosphorus cycle.

但是土壤中的很多磷会被雨水或者融雪冲刷到河水中。

But a lot of the Phosphorus in the soil gets washed away into rivers by rain and melting snow.

那么就开始了另一种阶段的循环。

And so begins another phase of the cycle.

Can anyone guess what it is called? Nancy?

南希：呃，那个既然叫做陆地阶段循环，那么这个应该叫做水阶段循环。

Nancy: Well, if the one is called the land phase, then this has to be called the water phase, right?

教授：是的。这是一个难点，是吧?

Professor: Yes, that’s such a difficult point, isn’t it?

在正常的水阶段循环中，河水会最终倾泻到海洋，一旦进入海洋，磷就会被海藻之类的植物所吸收。

In a normal water phase, rivers eventually empty into oceans, and once in the oceans, the Phosphorus gets absorbed by water plants like algae.

鱼吃了这些海藻，或者吃了是其它吃了海藻的鱼。

Then fish eats the algae or eat other fish that have eaten those plants.

但是水循环阶段会被过剩的肥料所影响。

But the water phase is sometimes affected by excessive fertilizers.

如果不是所有的磷被作物吸收，那么大量的磷会进入河水，这就会引起水下植物的迅速生长，最终导致有机体在水中产生堵塞，这就会改变河水的流动。

If not all of Phosphorus gets used by the crops and large amounts of Phosphorus gets into the rivers, this could cause a rapid growth of water plants in the river, which can lead to the water ways getting clogged with organisms, which can change the flow of the water.

目前人们针对这些影响在做一些研究，我真的希望能在生态系统遭到破坏之前找到应付这个问题的方法。明白了吗？

Several current studies are looking at these effects and I really do hope we can find the way to deal with this issue before these ecosystems are adversely affected. Ok?

好了，当然，人们还有一种干预正常过程的方式——捕鱼。

Of course, another way that humans can interrupt the normal process is fishing.

The fishing industry helps bring Phosphorus back to land.

在正常的水阶段循环中，磷会进入海洋底部，与海洋沉淀物混合在一起。

In the normal water phase the remaining Phosphorus makes its way, settles to the bottom of the ocean and gets mixed into ocean sediments.

海洋深处的磷还需回到海洋表面，来完成循环，然后从头开始在此循环。

The Phosphorus at the bottom of the ocean has to somehow make its way back to the surface, to complete the cycle, to begin the cycle all over again.

几百万年后，强烈的地质作用，如地下火山会提升海洋并形成陆地。

After millions of years, powerful geological forces, like underwater volcanoes, lift up the ocean sediments to form new land.

当地下火山推动海底岩石到表面时，新陆地形成。

When a underwater volcano pushes submerged rock to the surface, a new island is created.

多年后磷会到达新陆地并开始腐蚀，循环再继续。

Then over many more years the Phosphorus-rich rocks of the new land begin to erode and the cycle continues.

学生：那么，您刚才说氮循环也是很重要的养分循环。

Guy: What about, well, you said that the nitrogen cycle is also an important nutrient cycle.

而大气层中有很多的氮，所以我在想，大气层中也有很多的磷吗？

And there is a lot of nitrogen in the atmosphere, so I was wondering, is there a lot of Phosphorus in the atmosphere, too?

你猜测磷会到达地球大气层的想法是对的。

You’re right to guess the Phosphorus can end up in Earth’s atmosphere.

它可以从陆地或者海洋到达大气层中，反之亦然。

It can move from the land or from the oceans to the atmosphere, and vice versa.

However, there’s just not a substantial amount of it there, like there is with nitrogen.

Which human activities that influence the phosphorus cycle does the professor mention?

Why does the professor discuss underwater volcanoes?

What can be inferred about the professor 's view on phosphorus getting washed into rivers?

What comparison does the professor make involving phosphorus and nitrogen?

What does the professor mean when she says this :

A: So, we’ve been talking about nutrients, the elements in the environment that are essential for living organisms to develop, live a healthy life and reproduce. Some nutrients are quite scarce. They are just isn’t much of them in the environment but fortunately they get recycled. When nutrients are used over and over in the environment, we call that a nutrient cycle. Because of the importance of nutrients and their scarcity, nutrient recycling is one of the most significant ecosystem processes that will cover in this course. The three most important nutrient cycles are the Nitrogen cycle, the Carbon cycle and one more we are going to talk about today, the Phosphorus cycle. So the phosphorus cycle has been studied a lot by ecologists because like I said, phosphorus is an important nutrient and it’s not so abundant. The largest quantities are found in rocks at the bottom of the ocean. How does the phosphorus get there? Well, let’s start with the phosphorus in rocks. The rocks get broken down into smaller and smaller particles as they are weathered. They are weathered slowly by rain and wind over long periods of time. Phosphorus is slowly released as the rocks broken down and it gets spread around into the soil. Once it’s in the soil, plants absorb it through their roots. 
B: So that’s the reason people mine rocks that contain a lot of phosphorus to help the agriculture? 
A: Ah ha. They mine the rock, artificially break it down and put the phosphorus into the agricultural fertilizers. So humans can play a role in the first part of phosphorus cycle, the breaking down of rocks and spreading of phosphorus into the soil by speeding up the rate at which this natural process occurs, you see? Now, after the phosphorus is in the soil, plants grow. They use phosphorous in the soil to grow, and when they die they decompose and pho 
B: Eh, well, if the one is called the land phase, then this has to be called the water phase, right? 
A: Yes, that’s such a difficult point, isn’t it? In a normal water phase, rivers eventually enter into oceans and once in the oceans, the phosphorus gets absorbed by water plants like algae. Then fish eat the algae or eat other fish that have eaten those plants. But the water phase is sometimes affected by excessive fertilizers. If not all of the phosphorus gets used by the crops and large amounts of phosphorus gets into the rivers, this could cause a rapid growth of water plants in the river which can lead to the water wastes getting clogged with organisms which can change the flows of the water. Several current studies are looking at these effects and I really do hope we can find a way to deal with this issue before the ecosystem are adversely affected. OK, of course, another way that humans can interrupt the normal process is fishing. The fishing industry helps bring phosphorus back to land. In the normal water phase, the remaining phosphorus makes its way, settles to the bottom of the ocean and gets mixed into ocean settlements. 
But remember, this is a cycle. The phosphorus at the bottom of the ocean has to somehow make its way back to the surface to complete the cycle to begin the cycle all over again. After millions of years, powerful geological forces like underwater volcanoes lift up the ocean settlements to form new land. When an underwater volcano pushes sub-merged rock to the surface, a new island is created. Then over many more years ofthe phosphorus reach rocks of the new land began begin to a roaderode and the cycle continues. 
A: Yes, that’s such a difficult point, isn’t it? In a normal water phase, rivers eventually enter into oceans and once in the oceans, the phosphorus gets absorbed by water plants like algae. Then fish eat the algae or eat other fish that have eaten those plants. But the water phase is sometimes affected by excessive fertilizers. If not all of the phosphorus gets used by the crops and large amounts of phosphorus gets into the rivers, this could cause a rapid growth of water plants in the river which can lead to the water wastes getting clogged with organisms which can change the flows of the water. Several current studies are looking at these effects and I really do hope we can find a way to deal with this issue before these ecosystems are adversely affected. OK, of course, another way that humans can interrupt the normal process is fishing. The fishing industry helps bring phosphorus back to land. In the normal water phase, the remaining phosphorus makes its way, settles to the bottom of the ocean and gets mixed into ocean settlements. 
C: What about, well, you said that Nitrogen cycle is also an important nutrient cycle, and there’s a lot of Nitrogen in the atmosphere, so I was wondering, is there a lot of phosphorus in the atmosphere too? 
A: Good question, George. You are right to guess the phosphorus can end up an earth atmosphere. It can move from the land or from the oceans to the atmosphere and vice versa. However, there’s not just a substantial amount of it there, like there is with Nitrogen. It’s a very minimal quantity. 
B: Eh, well, if the one is called the land phase, then this has to be called the water phase, right? 
A: Yes, that’s such a difficult point, isn’t it?