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第1段
1 .<-NARRATOR:-> Now listen to part of a lecture from an environmental science class.
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第2段
1 .<-MALE PROFESSOR:-> Okay, so an example of this is when chickens are used to prepare a field for planting.
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2 .Farmers who do this have a special kind of little house that they keep their chickens in.
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3 .This little house has four walls and a roof,
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4 .but it doesn't have any floor.
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5 .And it has wheels attached to it
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6 .so it can easily be moved from one location to another.
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第3段
1 .So, farmers move this little house to a field where something is going to be planted-
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2 .say, bean plants...
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3 .and then the chickens are placed inside the house...
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4 .Now remember, there's no floor in this house.
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5 .And what the chickens do is,
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6 .they walk around inside the house
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7 .and peck at the soil
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8 .and eat any weeds or wild plants that they find...
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9 .And then, when the chickens' re done eating the weeds in that location,
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10 .the farmers move the house to the next section of the field...
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11 .and again the chickens peck at the soil and eat the weeds.
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12 .So the chickens get to eat lots of weeds, which are good for them.
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第4段
1 .Now, this activity's also good for the bean plants that'll be growing in the field...
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2 .because when the chickens eat the weeds,
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3 .they're improving the quality of the soil.
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4 .Thanks to the chickens,
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5 .when the bean plants start to grow,
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6 .there won't be any weeds there to compete with them for crucial resources
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7 .like sunlight and water.
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