What are 3 structures (other than appearance) that you can look at to determine how closely related different species are?

Thus, scientists can look for similarities in the DNA and amino acid sequence to determine how closely related the two species are. The characteristics of an organism are determined by its genes, which are nothing but specific sequences of DNA molecules. Homologous structures provide evidence for common ancestry, while analogous structures show that similar selective pressures can produce similar adaptations (beneficial features). Similarities and differences among biological molecules (e.g., in the DNA sequence of genes) can be used to determine species' relatedness.

Explanation:

"a.) well–developed vascular system."