Things used to be so simple! You had animals and you had plants. If it moved around under it's own power, it was an animal. If it didn't, it was a plant, unless you were odd-balls like corals. Then someone had to point out that fungi aren't really plants, and neither are bacteria (whom we managed to keep from calling animals even if some of them did move around). Someone else pointed out that botanists and zoologists both claimed some tiny creatures, and maybe we ought to consider them as a whole other group, the protists.
So there we were, with four kingdoms instead of two. Then a bunch of
trouble-makers, AKA molecular biologists, got involved and noted that there really were
two very different kinds of bacteria—and suddenly we had five kingdoms. We really
shouldn't have encouraged the molecular types; now they're busily dividing up
the protists into heaven knows how many kingdoms. The way things are going, it's
going to be no big deal to offer a kingdom for a horse—they're going to be a dime a
dozen!
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.