In the movie, “Signs”, one of the characters, Bo, has an interesting habit of leaving half-full glasses of water lying around the house. To Bo, the water “tastes funny” after she drinks only a few sips of it. This odd habit becomes instrumental in the story’s ending. (I will not spoil it for those of you who have never watched this film!)

Incidentally, water can taste funny due to substances and/or forms of life found in it.    Too bad Bo wasn’t a scientist.  Perhaps she could have extracted DNA from each glass of water and found out the kinds of organisms that have existed in this water.

Dutch scientists (Thomsen et. al., 2011) have been successful in identifying organisms that have been swimming through as little as a cup of freshwater. These scientists claim that organisms that swam through these waters within two weeks of collection left traces of DNA behind. This is quite a useful tool in determining the ecology of any given freshwater area. Scientists can use this information to identify rare or invasive species and monitor the activity of organisms found in a particular habitat within a period of time.

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