WAEC - Biology (2017 - No. 42)
The type of variation illustrated above is
continuous variation
discontinuous variation
morphological variation
environmental variation
Erläuterung
The rolling of the tongue is an example of discontinuous variation. This type of variation describes traits that fall into distinct categories, with no intermediates. In the case of tongue rolling, individuals are either able to roll their tongue or they are not. There's no "partial rolling".