Final answer:
The color of a butterfly is a morphological trait, and the shift towards dark-colored moths since the Industrial Revolution is an example of directional selection. Observable traits are collectively known as an organism's phenotype.
Step-by-step explanation:
The coloration of a butterfly, whether dark or light, is an example of a morphological trait. This term refers to the physical characteristics that can be observed, such as color and structural morphology. When talking about the Industrial Revolution and the increase in the number of dark-colored moths, this phenomenon is an example of directional selection, where a certain phenotype becomes more common in a population due to changes in the environment that make it more advantageous for survival. The observable traits like color that an organism expresses are referred to as its phenotype.