Final answer:
Genetic material is transmitted in terms of alleles instead of genotypes. Analyzing alleles allows for the study of how selective forces change a population and contribute to genetic diversity.
Step-by-step explanation:
Genetic material is transmitted from one generation to the next in terms of alleles instead of genotypes because an allele is a specific form or variant of a gene that can produce a particular trait. Each individual in a population can carry two alleles for a particular gene, but there can be more than two alleles in the population. By analyzing the transmission of alleles, population geneticists can study how selective forces change a population through changes in allele frequencies, which contribute to genetic diversity. For example, in the ABO blood type system, three different alleles determine the specific blood type protein on red blood cells.