An important turning point for evolutionary theory was the birth of population genetics, which emphasizes the extensive genetic variation within populations and recognizes the importance of:

Explanation

The correct answer is quantitative characters. These traits, which can be measured and quantified, like height or weight, are essential for the study of population genetics. They allow scientists to analyze how traits are distributed and inherited within populations. Qualitative characters are less central to population genetics because they don't provide the continuous data needed for such analyses. Analytical characters are not a recognized term in this context, and morphological characters, while important in other areas, are not the primary focus of population genetics.