TPO59听力Lecture1原文+MP3+题目+答案下载

TPO59听力Lecture1原文+MP3+题目+答案

TPO59听力Lecture1原文：

listen to part of a lecture in an ecology class. so we've spent a lot of time in this class studying ecosystems sand. Now I wanna talk about a specific instance of an ecosystem changing over time, changing significantly. And um, unexpectedly, uh, I'm talking about the illusion islands, um, off the coast of alaska. the illusion islands up until the 18th century were grassland ecosystem. now the grasslands on some of the islands have disappeared. And what we have there now is tundra, primarily low scrubby vegetation. and and this started happening in the 18th century. Okay, so why jeff？

um excuse me, professor. I thought. tundra referred to frozen ground. Wouldn't all the islands have that?

okay right. tundra often refers to a region where the underground soils permanently frozen. and and the primary vegetation is moss, lichen, and maybe a few dwarf shrubs. But it's the vegetation that classifies a region as tundra, not the temperature of the soil. anyway, in the 18th century, traders introduced foxes on to the islands, and those fox's preyed on the ground nesting sea birds. you're saying that change the entire ecosystem. oh, yes. And drastically introducing a single species can gradually transform an entire ecosystem. and a study that was done on the illusion island shows one way this can happen. um.

So all right, the foxes were introduced and the most obvious impact was a decrease of the sea bird population. that's a direct impact. Right? the fox is preyed on the sea, birds, and they started to disappear. well, there were indirect effects to changes in the soil and vegetation. And these effects weren't obvious. For a long time.

TPO59听力Lecture1题目：

1. What is the lecture mainly about?

A. Differences between tundra and grassland ecosystems

B. Reasons seabirds prosper in an island ecosystem

C. Why introduced species have difficulty adapting to a new ecosystem

D. How introduced species can affect ecosystems

2. What initially caused the ecosystem of some of the Aleutian Islands to change?

A. Traders brought a new species of mammal to some of the islands

B. Scientists introduced a new species of grass on some of the islands

C. The temperature of the soil suddenly decreased on some of the islands

D. The population of nest-building seabirds increased on some of the islands

3. The professor mentions that some of the Aleutian Islands were deprived of ocean-derived nutrients. What was the direct resu lt of the deprivation?

A. A rise in the fox population

B. An absence of seabirds

C. A change in the vegetation

D. The exposure of volcanic rock

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