Peppered moths make a compelling case study in natural selection. A classic illustration of "survival of the fittest." ![]() As the cities reduced the pollution, the tree trunks lightened up, and so did the moths. Eventually, black became the norm for urban peppered moths. Better camouflaged than their light-colored brethren, the dark forms survived and proliferated. In a short time, though, dark variants of the moths sprang up. Coal soot from burgeoning industry gradually blackened tree trunks in urban areas, and left the moths more vulnerable to predators. In pre-industrial England, most peppered moths had mottled grey wings, camouflaging well with the birch trees upon which they rested. The story is reminiscent of the peppered moth lesson from high school biology class. Almost all of the mice collected from the volcanic formations had dark coats-the better to stay concealed from hungry owls, which can pick off mice from contrasting backgrounds even at night. Nachman's group collected pocket mice from two of these black rock islands-the Pinacate formation in southwestern Arizona and the Pedro Armendaris formation of New Mexico. But scattered throughout the southwest are islands of black basaltic rock formed from not-so-ancient lava flows. ![]() Most of the mice have light tawny fur, which blends in well with the desert granite substrates they typically inhabit. ![]() Nachman, examined the coat colors of rock pocket mice. The group, led by Professor of ecology and evolutionary biology Michael W.
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