in a muddy lake environment, some fish have brown scales. Most fish, however, have silver scales. Predators have a harder time seeing fish with brown scales, which means that brown scales are an
advantageous adaptive trait in this environment. Over time, more and more fish will develop brown scales as a result of natural selection, as those with this trait are more likely to survive and pass on their genes to the next generation. This process is called evolution by natural selection.
