A Level Biology Practice Exam

What type of variation results in distinct, separate values, such as blood type?

1. continuous variation

2. discontinuous variation

3. quantitative variation

4. phenotypic variation

The correct answer is: discontinuous variation

Discontinuous variation refers to traits that are categorized into distinct groups or categories, with no intermediate values. Blood type is a prime example of discontinuous variation as it can be classified strictly into categories such as A, B, AB, and O, without any blending or gradual changes between these groups. This type of variation occurs due to the presence of specific alleles that lead to certain phenotypes, presenting clear demarcations rather than a smooth range of variations as seen in continuous traits. Continuous variation, in contrast, involves traits that show a range of phenotypes, such as height or skin color, where individuals can express any value within a spectrum. Quantitative variation is closely related and often overlaps with continuous variation, focusing on traits influenced by multiple genes. Phenotypic variation encompasses all observable traits but does not specifically refer to the distinct groupings as seen in discontinuous traits. Thus, when considering traits like blood type, it is clear that the characteristics align with discontinuous variation, leading to distinct classifications.