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tionaryfrom 1969 doesn’t recognize the term。）many organisms in the visible world were also poorly served by the traditional division。
fungi； the group that includes mushrooms； molds； mildews； yeasts； and puffballs； were nearlyalways treated as botanical objects； though in fact almost nothing about them—how theyreproduce and respire； how they build themselves—matches anything in the plant world。
structurally they have more in mon with animals in that they build their cells from chitin；a material that gives them their distinctive texture。 the same substance is used to make theshells of insects and the claws of mammals； though it isn’t nearly so tasty in a stag beetle as ina portobello mushroom。 above all； unlike all plants； fungi don’t photosynthesize； so theyhave no chlorophyll and thus are not green。 instead they grow directly on their food source；which can be almost anything。 fungi will eat the sulfur off a concrete wall or the decayingmatter between your toes—two things no plant will do。 almost the only plantlike quality theyhave is that they root。
even less fortably susceptible to categorization was the peculiar group of organismsformally called myxomycetes but more monly known as slime molds。 the name no doubthas much to do with their obscurity。 an appellation that sounded a little more dynamic—“ambulant self…activating protoplasm；” say—and less like the stuff you find when you reachdeep into a clogged drain would almost certainly have earned these extraordinary entities amore immediate share of the attention they deserve； for slime molds are； make no mistake；among the most interesting organisms in nature。 when times are good； they exist as one…celled individuals； much like amoebas。 but when conditions grow tough； they crawl to acentral gathering place and bee； almost miraculously； a slug。 the slug is not a thing ofbeauty and it doesn’t go terribly far—usually just from the bottom of a pile of leaf litter to thetop； where it is in a slightly more exposed position—but for millions of years this may wellhave been the niftiest trick in the universe。
and it doesn’t 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’t really belong anywhere。 when genetic testingarrived； people in lab coats were surprised to find that slime molds were so distinctive andpeculiar that they weren’t 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—kingdoms； as they are known—calledanimalia； 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’s new scheme was a great improvement； protista remained ill defined。
some taxonomists reserved it for large unicellular organisms—the eukaryotes—but otherstreated it as the kind of odd sock drawer of biology； putting into it anything that didn’t 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’s a lot of odd socks。
ironically； just as whittaker’s 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—or about as early as it was possible to do so—he 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’t 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； “like learning about animals from visiting zoos。”
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—something 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 pept