2024年4月29日发(作者：康佳电视怎么样质量怎么样)

TPO67阅读-3TaxonomyofOrganisms

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原文

TaxonomyofOrganisms

①Classificationschemesareusedbybiologiststoplacethehugenumberof

y,thesegroupingsaremadeby

axonomistsuse

suchfeaturesasanatomy,developmentalstages,andbiochemicalsimilaritiesto

lassificationschemesplacedallorganismsintoeither

,closeexaminationoftheuniquestructureof

fungiandthediversityofsingle-celledorganismsmadeitnecessarytopropose

additionalkingdomsthatrecognizedthefundamentaldifferencesamongplants,

animals,fungi,andunicellularprokaryotes(organismswhosecellsdonothavea

distinctmembrane-boundnucleus)andeukaryotes(organismswhosecellshavea

distinctmembrane-boundnucleus).Thecurrentschemeconsistingoffive

kingdoms—Monera,Protista,Animalia,Fungi,andPlantae—wasdevisedin

responsetothisneed.

②ar7000to

10,alnumberofnamedspeciesiscurrently

r,manyscientistsbelievethat7millionto10million

speciesmayexist,fthespecies

thathavebeenidentified,about5percentareintheMoneraandProtista

tional22percentareplantsandfungi,andtherestareanimals.

Thisdistributionhaslittletodowiththeactualabundanceoftheseorganismsand

alottodowiththesizeoftheorganisms,howeasytheyaretoclassify,andthe

numberofscientistsstudyingthem.

③ThekingdomProtista,definedascomprisingallsingle-celledeukaryotic

organisms,isnotanaturalgrouping,andscientistsdisagreeaboutwhich

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,animals,andfungiallhavecloseprotistan

relatives,andtheseparationofsingle-celledorganismsfrommulticellular

peciallysoforthealgae,whichhave

bothsingle-celledandmulticellularrepresentativeswithinmostsmallertaxonomic

selyrelatedorganismsbeplacedintoseparatekingdoms,

ProtistaandPlantae,simplyonthebasisofmulticellularity?Ifyoulookatdifferent

textbooks,youwillseethatthealgae,photosyntheticorganismswithsimple

reproduction，aresometimesplacedentirelyintoProtista,andsometimestheyare

splitbetweenProtistaandPlantaedependingonwhethertheyaresinglecelledor

xonomistssplitthemulticellularalgaeintotwokingdoms,

placingthemulticellularbrownandredalgaewiththeprotistsandthe

ifferentattemptsto

classifycloselyrelatedorganismsaregoodexamplesofhowdifficultitisto

developstandardcriteriaforgroupingorganisms,evenatthekingdomlevel.

④Oneapproachtothisproblem,enthusiasticallyendorsedbyLynnMargulis,a

biologistattheUniversityofMassachusetts,isthecreationofthekingdom

xonomiccategorywouldincludesingle-celledorganismsand

theirclosedescendants(forexample,themulticellularalgaebutnottheanimals,

fungi,andplants).MargulisdescribesthekingdomProtoctistaas“theentire

motleyandunrulygroupofnonplant,nonanimal,nonfungalorganisms

representativeoflineagesoftheearliestdescendantsoftheeukaryotes.”

⑤Itisconceptuallydifficulttogrouponeofthelargestmulticellularorganismsin

theworld,thebrownalgaecalledgiantkelps,withsimplemicroscopicsingle-celled

,someofwhichareupto60meterslong,possessatissuelikelevel

oforganizationthatisrelativelycomplexandcantransportmaterialsoverlong

distances,lsinkelpsandsomeother

r,kelpsreproducelike

Cavalier-SmithoftheUniversityof

BritishColumbiahasproposedthatbrownalgaemerittheirownkingdom

(kingdomChromista)basedonultrastructuralfeaturesandmolecularcomparisons

,evenamongthealgae,therearecleardifferencesthatsome

scientistsbelievearesufficienttojustifythestatusofaseparatekingdom.

⑥Aswelearnmoreabouttherelationshipsbetweenorganismsandrefinethe

criteriausedtoclassifythem,

superficiallysimplequestion“Inwhichkingdomshouldweplacethealgae?”

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