英语听力文摘 English Digest 49、鱼喝水吗

　　Fish live in water, but do they drink it?
The answer is yes, but how fish drink water depends on where they live.
Water gets into a fish's body through osmosis, the process in which water diffuses¹ from a higher to a lower concentration. For example, if there is more water outside of a cell than inside, water will try to flow into the cell until there is the same concentration of water on either side of the cell's membrane². The body of a fish acts the same way, either absorbing or losing water depending on its surroundings.
Whether a fish absorbs or loses water is based on the fact that all fish must maintain a certain amount of salt in their bodies to stay healthy. Fish that live in fresh water have a higher concentration of salt in their bodies than the surrounding water. Consequently, water continuously flows into the fish's body to attempt to dilute³ the amount of salt in the fish until it is equal to the amount of salt in the surrounding water. Since fish cannot allow their salt content to be diminished, their kidneys work overtime⁴ to expel excess water in the form of urine.
Ocean fish have the opposite problem. Surrounded by salt water, their bodies contain a relatively⁵ lower concentration of salt than the ocean water. In this case osmosis causes the fish to constantly lose water in order to equalize salt concentration inside and outside the fish. to partially⁶ compensate⁷ for the water loss, ocean fish actually drink water through their mouths. And to get rid of the excess salt they take in by drinking seawater, they excrete some salt through cells in their gills.

1 diffuses   

（使光）模糊，漫射，漫散( diffuse的第三人称单数 )； （使）扩散； （使）弥漫； （使）传播

参考例句：

• A gas in solution diffuses from region of greater to one of less concentration. 溶液中的气体由浓度较高的区域向浓度较低的区域扩散。
• The sun diffuses light and heat. 太阳发出光和热。

2 membrane   

n.薄膜，膜皮，羊皮纸

参考例句：

• A vibrating membrane in the ear helps to convey sounds to the brain.耳膜的振动帮助声音传送到大脑。
• A plastic membrane serves as selective diffusion barrier.一层塑料薄膜起着选择性渗透屏障的作用。

3 dilute   

vt.稀释，冲淡；adj.稀释的，冲淡的

参考例句：

• The water will dilute the wine.水能使酒变淡。
• Zinc displaces the hydrogen of dilute acids.锌置换了稀酸中的氢。

4 overtime   

adj.超时的，加班的；adv.加班地

参考例句：

• They are working overtime to finish the work.为了完成任务他们正在加班加点地工作。
• He was paid for the overtime he worked.他领到了加班费。

5 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

6 partially   

adv.部分地，从某些方面讲

参考例句：

• The door was partially concealed by the drapes.门有一部分被门帘遮住了。
• The police managed to restore calm and the curfew was partially lifted.警方设法恢复了平静，宵禁部分解除。

7 compensate   

vt.补偿，赔偿；酬报 vi.弥补；补偿；抵消

参考例句：

• She used her good looks to compensate her lack of intelligence. 她利用她漂亮的外表来弥补智力的不足。
• Nothing can compensate for the loss of one's health. 一个人失去了键康是不可弥补的。