1. Evolutionary inertia: Evolution is a slow process, and some traits may persist in a species even after they have lost their original function. In the case of diurnal frogs, they may have inherited the genes for night vision from their nocturnal ancestors, and these genes have not been eliminated through natural selection because they do not have any negative consequences for the frogs' survival.
2. Pleiotropy: Many genes have multiple functions, and the genes associated with night vision may also have other important roles in the frogs' physiology or behavior. For example, some of these genes may be involved in the production of proteins that are essential for the frogs' overall health, and they may have been retained even though they are no longer needed for night vision.
3. Changes in environmental conditions: Although diurnal frogs are currently active during the day, it is possible that their ancestors were nocturnal. If the environmental conditions changed over time, such as the availability of food or the presence of predators, the frogs may have shifted their activity to the daytime, but they retained the genes for night vision as a backup in case the conditions changed again.
4. Developmental constraints: The development of an organism is a complex process, and there may be constraints that prevent the complete loss of certain genes or traits. For example, the genes for night vision may be linked to other genes that are essential for the development of the frogs' eyes, and eliminating the night vision genes could also disrupt the development of other important structures.
Overall, the retention of genes associated with night vision in diurnal frog species is likely due to a combination of these factors, and it highlights the complex nature of evolutionary processes.
