House cats and pumas and fishing c= ats all have a similarity to one another=2C just like tigers to lions=2C bu= t neither is particularly close to cheetahs=3B thus=2C cheetahs are alone i= n their genus (all their siblings are dead). Similarly=2C field mice have= extant relatives all over the place=2C cladistically...tuataras=2C aardvar= ks and pangolins don't. The way I learned it=2C ranks also demonstrate how = distinct something is from everything else.
They pretend to do that, too, but they don't. That's because "distinct" has never been quantified.
Oh, there have been a few extremely short-lived attempts to define ranks as times of origins of taxa: everything that originated in the Cretaceous would become, I don't know, an order, and so on. In addition to the obvious problems, _any_ such scheme would cause such enormous upheaval that you might just as well abandon ranks altogether...