万物简史英文版_比尔·布莱森- 第94节

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�。　familiar　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�or　a　鈥渟plitter；鈥潯�as　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�in　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�is　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　ofprimate。　oftentimes　it　turned　out　that　the　same　species　had　been　described　more　than　once鈥�sometimes　several　times鈥攚ithout　any　of　the　discoverers　realizing　that　they　were　dealing　withan　animal　that　was　already　known　to　science。　it　took　groves　four　decades　to　untangleeverything；　and　that　was　with　a　paratively　small　group　of　easily　distinguished；　generallynoncontroversial　creatures。　goodness　knows　what　the　results　would　be　if　anyone　attempted　asimilar　exercise　with　the　planet鈥檚　estimated　20；000　types　of　lichens；　50；000　species　ofmollusk；　or　400；000…plus　beetles。

what　is　certain　is　that　there　is　a　great　deal　of　life　out　there；　though　the　actual　quantities　arenecessarily　estimates　based　on　extrapolations鈥攕ometimes　exceedingly　expansiveextrapolations。　in　a　well…known　exercise　in　the　1980s；　terry　erwin　of　the　smithsonianinstitution　saturated　a　stand　of　nineteen　rain　forest　trees　in　panama　with　an　insecticide　fog；then　collected　everything　that　fell　into　his　nets　from　the　canopy。　among　his　haul　（actuallyhauls；　since　he　repeated　the　experiment　seasonally　to　make　sure　he　caught　migrant　species）were　1；200　types　of　beetle。　based　on　the　distribution　of　beetles　elsewhere；　the　number　ofother　tree　species　in　the　forest；　the　number　of　forests　in　the　world；　the　number　of　other　insecttypes；　and　so　on　up　a　long　chain　of　variables；　he　estimated　a　figure　of　30　million　species　ofinsects　for　the　entire　planet鈥攁　figure　he　later　said　was　too　conservative。　others　using　thesame　or　similar　data　have　e　up　with　figures　of　13　million；　80　million；　or　100　millioninsect　types；　underlining　the　conclusion　that　however　carefully　arrived　at；　such　figuresinevitably　owe　at　least　as　much　to　supposition　as　to　science。

according　to　the　wall　street　journal；　the　world　has　鈥渁bout　10；000　active　taxonomists鈥濃�攏ot　a　great　number　when　you　consider　how　much　there　is　to　be　recorded。　but；　the　journaladds；　because　of　the　cost　（about　2；000　per　species）　and　paperwork；　only　about　fifteenthousand　new　species　of　all　types　are　logged　per　year。

鈥渋t鈥