What type of variation is characterized by clear-cut observable categories?

The type of variation characterized by clear-cut observable categories is discrete variation. Discrete variation occurs when individuals can be sorted into distinct categories based on specific traits, such as flower color (e.g., purple or white) or the ability to roll one's tongue (either the ability to roll it or not). This type of variation doesn’t show any intermediate forms; individuals fall into one category or another without blending.

In contrast, continuous variation involves traits that can take on a range of values and do not have distinct categories. Examples include height or skin color, which vary gradually rather than categorically. Polygenic traits result from the interaction of multiple genes, often leading to continuous variation as well. Quantitative variation typically refers to measurable traits that also show a range rather than distinct categories.