Answer:
See explanation
Step-by-step explanation:
According to Darwin, the determinant of the ability of species to thrive in their environment is their ability to develop favourable characteristics which enable them to survive in their environment. This ability to develop favourable characteristics is called natural selection.
These favourable characteristics are passed on from parents to offsprings and are responsible for the perpetuation of organisms having these favourable characteristics in comparison to other members of the same species.
In relation to Mendel's theory, these favourable characteristics could be regarded as Mendel's factors (currently identified as genes). These factors are units of inheritance passed on from parents to offsprings.
If Darwin had an idea of Mendel's work when he propounded his evolution theory, he could have modified his idea of favourable characteristics to imply genes. This would have made his idea more empirical than speculative and led to a faster world wide acceptance of his ideas.