The fewer the differences in the amino acid sequence of cytochrome c between two species, the

Explanation

Sequence differences accumulate by mutation after two lineages separate, so a small number of differences means little time has passed since they shared an ancestor. Human and chimpanzee cytochrome c is identical, while human and yeast differ at dozens of positions, and the pattern matches the tree built from anatomy and fossils. Genome size is unrelated to relatedness, as many amphibians have genomes far larger than ours.