You compare homologous nucleotide sequences among several pairs of species with known divergence times. A pair of species that diverged 1 million years ago has two nucleotide differences, a pair that diverged 2 million years ago has four nucleotide differences, and a pair that diverged 3 million years ago has six nucleotide differences. You have sequence data for another pair of species for which the divergence time is unknown. There are five nucleotide differences between them. Based on your clock, when did their line of ancestry diverge

2.5 million years is the divergence time.

Explanation:

If we see the pattern of divergence time in the first example it is 2 nucleotides difference it is 1 million years, 4 nucleotides it is 2 million years. With every one million years 2 nucleotide difference is seen. Based on this pattern it can be concluded that every 0.5 million years one nucleotide difference is seen. So,

for the 5 nucleotide difference in the sequenced data of another organism, it is 2.5 million years of divergence time.

The divergent time is important in knowing the evolution of a particular species.