RedEaredSlider writes: Fish in the Hudson River and the harbor in New Bedford, Mass., have evolved resistance to PCBs. In the Hudson, a species of tomcod has evolved a way for a very specific protein to simply not bind to PCBs, nearly eliminating the toxicity. In New Bedford, the Atlantic killifish has proteins that bind to the toxin (just as the do in mammals) but the fish aren't affected despite high levels of PCBs in their cells. Why the killifish survive is a mystery.
Five is a sufficiently close approximation to infinity.
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