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ugh； they crawl to acentral gathering place and bee； almost miraculously； a slug。 the slug is not a thing ofbeauty and it doesn鈥檛 go terribly far鈥攗sually just from the bottom of a pile of leaf litter to thetop； where it is in a slightly more exposed position鈥攂ut for millions of years this may wellhave been the niftiest trick in the universe。
and it doesn鈥檛 stop there。 having hauled itself up to a more favorable locale； the slimemold transforms itself yet again； taking on the form of a plant。 by some curious orderlyprocess the cells reconfigure； like the members of a tiny marching band； to make a stalk atopof which forms a bulb known as a fruiting body。 inside the fruiting body are millions ofspores that； at the appropriate moment； are released to the wind to blow away and beesingle…celled organisms that can start the process again。
for years slime molds were claimed as protozoa by zoologists and as fungi by mycologists；though most people could see they didn鈥檛 really belong anywhere。 when genetic testingarrived； people in lab coats were surprised to find that slime molds were so distinctive andpeculiar that they weren鈥檛 directly related to anything else in nature； and sometimes not evento each other。
in 1969； in an attempt to bring some order to the growing inadequacies of classification； anecologist from cornell university named r。 h。 whittaker unveiled in the journalscience aproposal to divide life into five principal branches鈥攌ingdoms； as they are known鈥攃alledanimalia； plantae； fungi； protista； and monera。 protista； was a modification of an earlier term； protoctista； which had been suggested a century earlier by a scottish biologist namedjohn hogg； and was meant to describe any organisms that were neither plant nor animal。
though whittaker鈥檚 new scheme was a great improvement； protista remained ill defined。
some taxonomists reserved it for large unicellular organisms鈥攖he eukaryotes鈥攂ut otherstreated it as the kind of odd sock drawer of biology； putting into it anything that didn鈥檛 fitanywhere else。 it included （depending on which text you consulted） slime molds； amoebas；and even seaweed； among much else。 by one calculation it contained as many as 200；000different species of organism all told。 that鈥檚 a lot of odd socks。
ironically； just as whittaker鈥檚 five…kingdom classification was beginning to find its wayinto textbooks； a retiring academic at the university of illinois was groping his way toward adiscovery that would challenge everything。 his name was carl woese （rhymes with rose）； andsince the mid…1960s鈥攐r about as early as it was possible to do so鈥攈e had been quietlystudying genetic sequences in bacteria。 in the early days； this was an exceedingly painstakingprocess。 work on a single bacterium could easily consume a year。 at that time； according towoese； only about 500 species of bacteria were known； which is fewer than the number ofspecies you have in your mouth。 today the number is about ten times that； though that is stillfar short of the 26；900 species of algae； 70；000 of fungi； and 30；800 of amoebas and relatedorganisms whose biographies fill the annals of biology。
it isn鈥檛 simple indifference that keeps the total low。 bacteria can be exasperatingly difficultto isolate and study。 only about 1 percent will grow in culture。 considering how wildlyadaptable they are in nature； it is an odd fact that the one place they seem not to wish to live isa petri dish。 plop them on a bed of agar and pamper them as you will； and most will just liethere； declining every inducement to bloom。 any bacterium that thrives in a lab is bydefinition exceptional； and yet these were； almost exclusively； the organisms studied bymicrobiologists。 it was； said woese； 鈥渓ike learning about animals from visiting zoos。鈥�
genes； however； allowed woese to approach microorganisms from another angle。 as heworked； woese realized that there were more fundamental divisions in the microbial worldthan anyone suspected。 a lot of little organisms that looked like bacteria and behaved likebacteria were actually something else altogether鈥攕omething that had branched off frombacteria a long time ago。 woese called these organisms archaebacteria； later shortened toarchaea。
it has be said that the attributes that distinguish archaea from bacteria are not the sort thatwould quicken the pulse of any but a biologist。 they are mostly differences in their lipids andan absence of something called peptidoglycan。 but in practice they make a world ofdifference。 archaeans are more different from bacteria than you and i are from a crab orspider。 singlehandedly woese had discovered an unsuspected division of life； so fundamentalthat it stood above the level of kingdom at the apogee of the universal tree of life； as it israther reverentially known。
in 1976； he startled the world鈥攐r at least the little bit of it that was paying attention鈥攂yredrawing the tree of life to incorporate not five main divisions； but twenty…three。 these hegrouped under three new principal categories鈥攂acteria； archaea； and eukarya （sometimesspelled eucarya）鈥攚hich he called domains。
woese鈥檚 new divisions did not take the biological world by storm。 some dismissed them asmuch too heavily weighted toward the microbial。 many just ignored them。 woese； according to frances ashcroft； 鈥渇elt bitterly disappointed。鈥潯ut slowly his new scheme began to catchon among microbiologists。 botanists and zoologists were much slower to admire its virtues。
it鈥檚 not hard to see why。 on woese鈥檚 model； the worlds of botany and zoology are relegatedto a few twigs on the outermost branch of the eukaryan limb。 everything else belongs tounicellular beings。
鈥渢hese folks were brought up to classify in terms of gross morphological similarities anddifferences；鈥潯oese told an interviewer in 1996。 鈥渢he idea of doing so in terms of molecularsequence is a bit hard for many of them to swallow。鈥潯n short； if they couldn鈥檛 see a differencewith their own eyes； they didn鈥檛 like it。 and so they persisted with the traditional five…kingdom division鈥攁n arrangement that woese called 鈥渘ot very useful鈥潯n his mildermoments and 鈥減ositively mis