Taxonomy

All living things have been organized rather loosely into a 7-entry taxonomy according to, in many cases, just appearance:

5 kingdoms — How they obtain their food

36 phylums (pjyla)  — Similar physical characteristics ... suggest similar ancestry

About 87 classes — Even more similar physical characteristics

Large number of orders —  Still more similar physical characteristics ... may have common ancestry

Very large number of families — Large number of physical characteristics ... have certain adaptive traits and may not have a common ancestry

Even larger number of genuses (geni) — The generic name for an organism ... always first used term. Each genus has only a few members

Varying number of species within geni — Determined by the ability to breed within species

See: Soft Schools Writeup for more on each of these categories.

Since we have now substantial DNA evidence on all organisms, I hope sometime soon that this taxonomy is recast along more solid scientific lines. I am actually surprised it hasn’t happened already.