Answer:
Disruptive selection and stabilizing selection enable the formation of a normal distribution curve. Normal Distribution in a graph can be indicated by the formation of a bell curve; when most of the values concentrate at the center and the distribution is symmetrically distributed.
Step-by-step explanation:
The three types of Natural Selection are; stabilizing selection, disruptive selection, and directional selection. These selections in a population are caused by the genetic traits that may be favored considering the species’ environment. Hence, natural selection is highly dependent on the characteristics that help the species to survive.
Stabilizing selection causes the graph to narrow down from both ends. For example, if we consider the birth weight of human babies, underweight babies are prone to illness while overweight babies are at risk of premature birth. This enables the extreme traits to discontinue while the shift is towards a healthy weight. This causes the curve to narrow down.
When we consider Disruptive Selection, the characteristics or the ‘phenotypes’ at both extremes are selected equally. This causes the graph to shift equally in both directions creating the aforementioned ‘normal distribution curve’.
However, when it comes to directional selection, the favorable characteristic is towards one side only, hence the graph is not normal.