Final answer:
The prevalence of genetically predisposed traits that have a reproductive advantage is best explained by natural selection. This is the process by which individuals with advantageous traits are more likely to survive, reproduce, and pass on their genes to the next generation.
Step-by-step explanation:
The prevalence of genetically predisposed traits that have a reproductive advantage is best explained in terms of natural selection. Natural selection is the process by which individuals with advantageous traits are more likely to survive, reproduce, and pass on their genes to the next generation. This leads to a gradual increase in the frequency of these traits within a population over time.
For example, let's consider a population of birds where some individuals have longer beaks and others have shorter beaks. If the environment changes in a way that makes obtaining food easier for birds with longer beaks, those individuals will have a reproductive advantage. They will be able to gather more food and have a higher chance of surviving and reproducing. As a result, the gene for longer beaks will become more common in the population over time.