> the whole kingdom-order-genus-species thing is muddy and ill-defined
Well yes, it's somewhat an arbitrary construct for human convenience, but isn't much of the muddiness down to our limited understanding of the true relationships?
Regarding "cadherin/catenin or how epithelia are formed to see how a tissue is much more than a bundle of cells." could you give a link cos this is so far outside my area I really don't know what to look for (wiki article on Catenin wasn't very revealing of your point, sorry if I missed it)