Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. The correct sequence is population, species, chromosomes, genes and then nucleotides from a higher to lower level. It becomes more specific from higher to lower level as the number of organisms keeps decreasing. It serves as a way for populations to adapt to changing environments. With more variation, it is more likely that some individuals in a population will possess variations of alleles that are suited for the environment.
So, the correct answer is 'Population, Species, Chromosomes, Genes, Nucleotides'.