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a few phyla are generally well known； such as mollusks （the home of clams and snails）；arthropods （insects and crustaceans）； and chordates （us and all other animals with a backboneor protobackbone）； though things then move swiftly in the direction of obscurity。 among thelatter we might list gnathostomulida （marine worms）； cnidaria （jellyfish； medusae；anemones； and corals）； and the delicate priapulida （or little 鈥減enis worms鈥潱！amiliar or not；these are elemental divisions。 yet there is surprisingly little agreement on how many phylathere are or ought to be。 most biologists fix the total at about thirty； but some opt for a numberin the low twenties； while edward o。 wilson in the diversity of life puts the number at asurprisingly robust eighty…nine。 it depends on where you decide to make your divisions鈥攚hether you are a 鈥渓umper鈥潯r a 鈥渟plitter；鈥潯s they say in the biological world。
at the more workaday level of species； the possibilities for disagreements are even greater。
whether a species of grass should be called aegilops incurva； aegilops incurvata； or aegilopsovata may not be a matter that would stir many nonbotanists to passion； but it can be a sourceof very lively heat in the right quarters。 the problem is that there are five thousand species ofgrass and many of them look awfully alike even to people who know grass。 in consequence；some species have been found and named at least twenty times； and there are hardly any； itappears； that haven鈥檛 been independently identified at least twice。 the two…volume manual ofthe grasses of the united states devotes two hundred closely typeset pages to sorting out allthe synonymies； as the biological world refers to its inadvertent but quite monduplications。 and that is just for the grasses of a single country。
to deal with disagreements on the global stage； a body known as the internationalassociation for plant taxonomy arbitrates on questions of priority and duplication。 at1to illustrate； humans are in the domain eucarya； in the kingdom animalia； in the phylum chordata； in thesubphylum vertebrata； in the class mammalia； in the order primates； in the family hominidae； in the genus homo；in the species sapiens。 （the convention； im informed； is to italicize genus and species names； but not those ofhigher divisions。） some taxonomists employ further subdivisions： tribe； suborder； infraorder； parvorder； andmore。
intervals it hands down decrees； declaring that zauschneria californica （a mon plant inrock gardens） is to be known henceforth as epilobium canum or that aglaothamniontenuissimum may now be regarded as conspecific with aglaothamnion byssoides； but notwithaglaothamnion pseudobyssoides。 normally these are small matters of tidying up thatattract little notice； but when they touch on beloved garden plants； as they sometimes do；shrieks of outrage inevitably follow。 in the late 1980s the mon chrysanthemum wasbanished （on apparently sound scientific principles） from the genus of the same name andrelegated to the paratively drab and undesirable world of the genus dendranthema。
chrysanthemum breeders are a proud and numerous lot； and they protested to the real ifimprobable…sounding mittee on spermatophyta。 （there are also mittees forpteridophyta； bryophyta； and fungi； among others； all reporting to an executive called therapporteur…g茅n茅ral； this is truly an institution to cherish。） although the rules of nomenclatureare supposed to be rigidly applied； botanists are not indifferent to sentiment； and in 1995 thedecision was reversed。 similar adjudications have saved petunias； euonymus； and a popularspecies of amaryllis from demotion； but not many species of geraniums； which some yearsago were transferred； amid howls； to the genus pelargonium。 the disputes are entertaininglysurveyed in charles elliott鈥檚 the potting…shed papers。
disputes and reorderings of much the same type can be found in all the other realms of theliving； so keeping an overall tally is not nearly as straightforward a matter as you mightsuppose。 in consequence； the rather amazing fact is that we don鈥檛 have the faintest idea鈥斺�渘oteven to the nearest order of magnitude；鈥潯n the words of edward o。 wilson鈥攐f the number ofthings that live on our planet。 estimates range from 3 million to 200 million。 moreextraordinary still； according to a report in the economist； as much as 97 percent of theworld鈥檚 plant and animal species may still await discovery。
of the organisms that we do know about； more than 99 in 100 are only sketchilydescribed鈥斺�渁 scientific name； a handful of specimens in a museum； and a few scraps ofdescription in scientific journals鈥潯s how wilson describes the state of our knowledge。 in thediversity of life； he estimated the number of known species of all types鈥攑lants； insects；microbes； algae； everything鈥攁t 1。4 million； but added that that was just a guess。 otherauthorities have put the number of known species slightly higher； at around 1。5 million to 1。8million； but there is no central registry of these things； so nowhere to check numbers。 in short；the remarkable position we find ourselves in is that we don鈥檛 actually know what we actuallyknow。
in principle you ought to be able to go to experts in each area of specialization； ask howmany species there are in their fields； then add the totals。 many people have in fact done so。
the problem is that seldom do any two e up with matching figures。 some sources put thenumber of known types of fungi at 70；000； others at 100；000鈥攏early half as many again。 youcan find confident assertions that the number of described earthworm species is 4；000 andequally confident assertions that the figure is 12；000。 for insects； the numbers run from750；000 to 950；000 species。 these are； you understand； supposedly the known number ofspecies。 for plants； the monly accepted numbers range from 248；000 to 265；000。 thatmay not seem too vast a discrepancy； but it鈥檚 more than twenty times the number of floweringplants in the whole of north america。
putting things in order is not the easiest of tasks。 in the early 1960s； colin groves of theaustralian national university began a systematic survey of the 250…plus known species ofpri