A process in nature in which organisms possessing certain genotypic characteristics that make them better adjusted to an environment tend to survive, reproduce, increase in number or frequency, and therefore, are able to transmit and perpetuate their essential genotypic qualities to succeeding generations.
A watchglass can be used as a beaker cover, but you can also place small amounts of chemicals on it and then heat it (for example, to evaporate some water from a wet chemical). From Wikipedia: A watch glass is a circular, slightly concave piece of glass used in chemistry as a surface to evaporate a liquid, or as a cover for a beaker. The latter use is generally applied to prevent dust or other particles entering the beaker; the watch glass does not completely seal the beaker, and so gas exchanges still occur.
A watch crystal is a transparent cover that protects the watch face. Note that, coincidently, the word crystal is also used to denote the tiny piece of quartz that serves as an oscillator in a quartz watch. These two types of crystals have nothing to do with each other. The latter is usually called a quartz crystal to prevent confusion.