Final answer:
Closely related species have almost identical genes but may have very different physical appearances. Unrelated organisms may look similar but have very different DNA sequences.
Step-by-step explanation:
Closely related species have almost identical genes but may have very different physical appearances.
For example, chimpanzees and humans share 99% of their genes and are very similar genetically. However, they have significant anatomical differences, such as the shape of their jaw and the relative lengths of their arms and legs.
On the other hand, unrelated organisms may look similar but have very different DNA sequences. The amount of shared DNA can be used to determine the degree of relatedness between species.