Can't see the changes in the soft parts and the biochemistry in the fossil record. As one moves lower in the list, the club is more exclusive. The more closely related two organisms are, the more levels they share, the more characteristics they share in common. Hierarchy of taxonomic groups. That is, an hypothesis of which species shared a common ancestor.
Homology is the similarity due to common ancestor.
Do not use analogous traits. Analogous - similar in function but arising from different ancestor. Both are protection from predators. One evolved in a group of insects the other in birds. See the figs.