The Hardy-Weinberg principle is not generally found in nature because it requires certain conditions in an environment. These conditions are the absence of the things that can cause evolution. In other words, if no mechanisms of evolution are acting on a population, evolution will not occur--the gene pool frequencies will remain unchanged.
Gum disease is a very common condition where the gums become swollen, sore or infected. The gums tend to bleed after you brush or floss your teeth, and the blood in your mouth causes the metallic taste. If left untreated, the tissues and bone that support the teeth can also become affected (known as periodontitis).
Is the taste in your mouth like metal? A metallic taste in your mouth is a some what common symptom, and metal tasting is typically not a serious problem. Your perception of a weird metallic mouth taste can be due to an assortment of factors. However, the most common causes of that bad taste of metal in mouth are medications used for treatment of: antibiotics.