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鱼生活在水里，那它们喝水吗?这个问题似乎有点多次一举，“水是生命的源泉”，似乎没有生物能离开水吧?鱼当然也离不开水，只不过它的饮水方式有点独特。
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
diffuses 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 membrane.
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 dilute 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 overtime to expel excess
water in the form of urine.
Ocean fish have the opposite problem. Surrounded by salt water, their
bodies contain a relatively 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 partially compensate 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.
osmosis: 渗透
dilute: 稀释 |
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发表于 2016-7-9 23:47:42