Phylogenetic classification?

Question

why is phylogenetic classification more natural than a system based on characteristics such as medical usefulness, or the shapes, sizes, and colors of body structures?

Answer 1

Phylogenics or phylogenetic classification is by definition related to or based on evolutionary development or history. In other words, phylogenetic classification attempts to place things in categories by the degree of evolutionary relatedness.  The more related things are, the more closely together the are placed within classification system.  

This type of system uses more inherent or natural characteristics to determine if things are related, in fact much of the fine level distinction between species is done with genetics.  Organisms that are very different can evolve into having similar size, color, and shape of body structures.

For example, tree ferns are large, and it might be tempting to group them with trees (classify them with trees), but they have a lot more in common with ferns, and evolved from simpler ferns,  than with angiosperm trees, so phylogenetically they are placed with ferns.