- 2018年01月31日18:12 来源：小站整理
- 参与（0） 阅读（722）
Narrator: Listen to part of a lecture in an Ecology Class.
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. Some nutrients are quite scarce; there 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 eco-system processes that we’ll cover in this course.
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. 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 and at the bottom of the ocean.
How does 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 are broken down and it gets spread around into the soil. Once it’s in the soil, plants absorb it through their roots.
Student: So that’s the reason people mine rocks that contain a lot of Phosphorus to help with agriculture?
Professor: Uh-huh, they mine the rock, artificially break it down and put the Phosphorus into agricultural fertilizers. 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. And when they die, they decompose. 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. We call all of this – the land phase of the Phosphorus cycle. But a lot of the Phosphorus in soil gets washed away into rivers by rain and melting snow. And so begins another phase of the cycle. Can anyone guess what it is called? Nancy?
Nancy: Well, if the one is called the land phase, then this has to be called the water phase, right?
Professor: Yes, that’s such a difficult point, isn’t it? In a normal water phase, rivers eventually empty into oceans, and once in the oceans, the Phosphorus gets absorbed by water plants like algae. Then fish eats 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 Phosphorus gets used by the crops and large amounts of Phosphorus gets into the rivers, this could cause 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. 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 sediments.
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 sediments to form new land. When an underwater volcano pushes submerged rock to the surface, a new island is created. Then over many more years the Phosphorus-rich rocks of the new land begin to erode and the cycle continues.
Guy: What about, well, you said that the nitrogen cycle is also an important nutrient cycle. And there is a lot of nitrogen in the atmosphere, so I was wondering, is there a lot of Phosphorus in the atmosphere, too?
Professor: Good question, George. You’re right to guess that Phosphorus can end up in Earth’s atmosphere. 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. It’s a very minimal quantity.
Question 1 of 6
What is the main purpose of the lecture?
A. To discuss environment phenomena that have changed the phosphorus cycle.
B. To illustrate how interrupting the phosphorus cycle can affect the environment.
C. To describe how phosphorus ends up in the atmosphere.
D. To explain how phosphorus gets recycled in the environment.
Question 2 of 6
Which human activities that influence the phosphorus cycle does the professor mention?Click on 2 answers.
B. Building dams on rivers.
C. Polluting the oceans.
D. marking and using fertilizer.
Question 3 of 6
Why does the professor discuss underwater volcanoes?
A. To describe the location of most of the phosphorus on Earth.
B. To point out the difficulty of studying the phosphorus cycle.
C. To describe a step in the phosphorus cycle.
D. To illustrate the differences between two phases in the phosphorus cycle.
Question 4 of 6
What can be inferred about the professor 's view on phosphorus getting washed into rivers?
A. She is unconcerned because phosphorus is a beneficial nutrient.
B. She is concerned about the quantity of phosphorus entering the waterways.
C. She thinks that the amount of research conducted on the topic is excessive.
D. She is frustrated that most of her students are unaware of the phenomenon.
Question 5 of 6
What comparison does the professor make involving phosphorus and nitrogen?
A. Sediment on the ocean floor contains more nitrogen than phosphorus.
B. The atmosphere contains more nitrogen than phosphorus.
C. Nitrogen requires more time to get recycled than phosphorus does.
D. Phosphorus is more important than nitrogen to the development of fish.
Question 6 of 6
What does the professor mean when she says this?
A. She realizes that the students are struggling with the concept.
B. She is surprised that the student knew the answer to her question.
C. She thinks that the answer to the question is obvious.
D. She thinks that this phase of the cycle has an unusual name.
Question 1 of 6
题目解析：在 lecture 的开头教授提到有些营养元素在自然界中的量不多，主要靠循环来得到充分利用，借此引出了nutrient cycle 这个概念，并且全文接下来都围绕这个内容讲述，所以答案应该选 D。
Question2 of 6
题目解析：教授提到了两种人类的行为会干扰到营养元素的循环。第一种是制作和使用肥料，humans can play a role in a first part of the Phosphorus cycle -- the breaking down of rocks and the spreading Phosphorus into the soil by speeding up the rate at which this natural process occurs;第二种是钓鱼，The fishing industry helps bring Phosphorus back to land。可以看出答案 A 和 D 是正确答案。
Question 3 of 6
题目解析：教授在描述phosphorus cycle的运作机理的时候提到，在海底的phosphorus 通过海底火山的爆发来到海洋表面，这是完成phosphorus cycle的一个步骤。所以答案应该选 C。
Question 4 of 6
题目解析：教授提到如果大量的phosphorus进入到河流中，将引起水流的变化，她希望有关研究可以尽快找到解决办法。所以这道题应该选 B，她对于 phosphorus 大量进入河流的现象持担忧态度。
Question 5 of 6
题目解析：教授说大气层中确实存在phosphorus，但 there’s just not as substantial amount of it there, like there is with nitrogen, it’s a very minimal quantity，即 phosphorus 的量在大气层中非常稀 少，而nitrogen 却比较多，所以答案应该选B。
Question 6 of 6
题目解析：这道题仅看教授说的话本身可能会错误选择答案 B，认为教授觉得这个问题很难，很惊讶学生能够回答。但是对于这一类型的题，比起句子本身，应该更加看重上下文综合起来 想要表达的意思，很明显 Nancy 做的这个推论非常直接和简单，所以这里教授这句话的意 思是“这个问题就只有这样的难度”，答案应该选C，教授提出的问题非常简单，答案很明显。