Final answer:
Characteristics that show many overlapping phenotypes, such as skin color and height in humans, are known as polygenic characteristics because they are controlled by multiple genes and alleles.
Step-by-step explanation:
Characteristics that exhibit many overlapping phenotypes are called polygenic characteristics. Polygenic characteristics are controlled by more than one gene, and each gene may have two or more alleles, which may be located on the same chromosome or on nonhomologous chromosomes. This contrasts with discontinuous variation, where individuals show a limited number of distinct traits with large differences between them.
Examples of polygenic characteristics in humans include skin color and adult height. These traits do not exhibit just one or two phenotypes but rather show a continuous variation in a population, typically resulting in a bell-shaped curve of distribution when plotted, with many individuals having a combination of dominant and recessive alleles. Continuous traits occur when offspring appear to be a "blend" of their parents' traits, revealing a spectrum of phenotypes rather than discrete categories.