TPO60听力Lecture3原文+MP3+题目+答案下载

TPO60听力Lecture3原文+MP3+题目+答案下载

TPO60听力Lecture3原文：

listen to part of a lecture in an ecology class. so we're. talking about biogeography. um, biogeography is the geographic distribution of plants and animals in an environment. and as you know, biogeography varies from ecosystem to ecosystem. now one, of ecosystem that we haven't discussed yet is the island environment. now, islands have always been interesting to study because their isolation makes them it it creates a kind of laboratory for examining their ecosystems. in the um, 1960s, robert macarthur and e o wilson developed a theory they called the equilibrium theory of island biogeography. and their theory states that. at. time islands achieve equilibrium, uh, a balance in terms of of the number of species of plants, animals, insects, etc. that they can support.

and they that is macarthur and wilson developed calculations to predict the point at which equilibrium is achieved, and the number of species that a given island would be able to sustain. um, according to. to their theory. This number, the the total number of species depends on two things, the size and location of the island, for example, they predict that there will be more species on bigger islands, and there will be more species on islands that are closer to the mainland. so, how does this work? according to. to macarthur and wilson, there are. two opposing. forces constantly at work in an island environment, pushing the island toward the state of equilibrium. the first force is the immigration rate. the immigration rate tracks the addition of new species to an island. then they argue that this rate declines over time, that there are more new species early on when the islands still empty, and there's little competition for space. however, as time progresses, there will be fewer and fewer new species that can compete with established species.

uh, it's not impossible for new species to be introduced at this late stage. It it might adapt better to summit it change in the evolving habitat, but it is definitely tougher. the second force is the extinction rate. and this is the rate at which species disappear from the island. in contrast with the immigration rate. This is a force that increases over time. in the beginning, when there's plenty of space, species don't need to compete with each other quite so much. but as species get settled on the island and the amount of space for each species declines, conditions become much more competitive. um, and and it's not just 。。。。。此处省略1000字原文

TPO60听力Lecture3部分题目：

1. What is the lecture mainly about?

A. Species that are typically associated with island ecosystems

B. Differences between island and mainland ecosystems

C. A model that predicts the number of species that an island can support

D. Reasons immigration rates must exceed extinction rates in island ecosystems

2. According to the lecture, what two factors will affect the number of species that can exist on an island?

Click on 2 answers

A. The number of volcanoes on the island

B. The size of the island

C. The location off he island

D. The human population on the is land

3. The professor describes the consequences for species as "an island becomes more crowded over t ime" . What consequences does she mention?

Click on 2 answers

A. Species become more vulnerable to extinction

B. One or two stronger species dominate the space

C. Old species disappear as the immigration rate increases

D. Each species will tend to be present in smaller numbers

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