Final answer:
Traits show continuous variation when multiple genes contribute to a single characteristic, resulting in a range of small differences among individuals, seeming to blend traits from parents.
Step-by-step explanation:
Some traits show continuous variation due to the action of many genes contributing to a single characteristic, such as human height or eye color. This genetic phenomenon appears to produce offspring that are a "blend" of their parents' traits. However, this is different from the blending theory of inheritance that was believed before Mendel's discoveries; he showed that traits are passed on as distinct entities through his work with discontinuous variation, using simple traits like flower color in peas which were not a blend but rather distinct traits inherited from each parent.