noms dans le fil d’Ariane
De radiaaldieren (Latynske namme: Radiata) foarmje in tuskenryk fan it ryk fan 'e bisten (Animalia) en it ûnderryk fan 'e echte dieren (Metazoa), dat tegearre mei it tuskenryk fan 'e twasidigen (Bilateria) ûnderbrocht wurdt by it rangleaze tuskentakson fan 'e weefseldieren (Eumetazoa). Radiaaldieren binne alsidich symmetrysk boude bisten, dy't in mûle hawwe mei dêromhinne in krâns fan tentakels. Se omfiemje fierders twa sellagen: in bûtenste (de ektoderm of bûtenhûd) en in binnenste (de endoderm of binnenhûd), wêrfan't de lêste de termholte beklaait. Soms wurdt foar de radiaaldieren ek de term holtedieren (Coelenterata) brûkt, mar dat moat ûntret wurde, mei't dy namme foarhinne ek brûkt waard om 'e spûnsdieren (Parazoa) oan te tsjutten.
It tuskenryk radiaaldieren bestiet út twa libbene stammen, wylst in trêdenien útstoarn is:
Ta de netteldieren hearre de skiifkwabben, polipen en koralen. Hoewol't in symmetryske lichemsbou yn 'e regel jûn wurdt as it definiëarjende skaaimerk fan radiaaldieren, fertoane guon netteldieren yn it larvale stadium in ûnmiskenbere twasidige symmetry. Dêrom tinke guon saakkundigen dat in twasidige symmetry him al earder ûntwikkele hawwe moat as by it útinoarfallen fan 'e radiaaldieren en de twasidigen, wat betsjutte soe dat symmetry yn radiaaldieren gjin primêr skaaimerk id. Sadwaande is de term 'radiaaldieren' no stadichoan út 'e graasje oan it reitsjen yn 'e wittenskip.
De radiaaldieren (Latynske namme: Radiata) foarmje in tuskenryk fan it ryk fan 'e bisten (Animalia) en it ûnderryk fan 'e echte dieren (Metazoa), dat tegearre mei it tuskenryk fan 'e twasidigen (Bilateria) ûnderbrocht wurdt by it rangleaze tuskentakson fan 'e weefseldieren (Eumetazoa). Radiaaldieren binne alsidich symmetrysk boude bisten, dy't in mûle hawwe mei dêromhinne in krâns fan tentakels. Se omfiemje fierders twa sellagen: in bûtenste (de ektoderm of bûtenhûd) en in binnenste (de endoderm of binnenhûd), wêrfan't de lêste de termholte beklaait. Soms wurdt foar de radiaaldieren ek de term holtedieren (Coelenterata) brûkt, mar dat moat ûntret wurde, mei't dy namme foarhinne ek brûkt waard om 'e spûnsdieren (Parazoa) oan te tsjutten.
Radiata zie e taxon oet 't oonderriek Eumetazoa (bieste mèt weefsele). Ze umvatte twie stamme: de nietelbieste (Cnidaria) en de ribkwalle (Ctenophora). 'nen Daarde stam zien de Trilobozoa (neet te verwarre mèt de trilobiete!), die in 't Ediacarium leefde.
't Taxon Radiata is vreuger ouch gebruuk veur oonder mie Spoonze, Stekelhuiege en Plakbieskes, meh later oonderzeuk heet zoe'n indeilinge achterhaold. Ouch de huiege, oetgekleide definitie gelt es parafyletisch: de Radiata höbbe geine veurawwer die de Bilateria (alle aander Eumetazoa, boe-oonder alle hoegoontwikkelde bieste) neet höbbe.
De Radiata oondersjeie ziech same mèt de Bilateria vaan de Spoonsechtege (Parazoa) doortot ze echte weefsele (nerve en spiere, wie sumpel ouch) höbbe, en doortot ze symmetrie kinne. Ze versjèlle vaan de Bilateria doortot neet twiezijeg, meh alzijeg symmetrisch zien (zègk mer gerös roond). Spoonze zien ouch dèks roond, meh misse echte weefsele. Stekelhuiege (ziestare en verwante) zien ouch drejsymmetrisch, meh vertuine es larf dudelek twiezijege symmetrie. Dit heet detouw geleid tot dees taxa vaan de Radiata woorte aofgeplits. Ouch binne de 'huiege' Radiata zien neet alle soorte ech drejsymmetrisch.
De Bilateria stamme dinkelek vaan de Radiata aof; welke plaots ze perceis in de stamboum mote innumme is oondudelek.
Radiata or Radiates is a historical taxonomic rank that was used to classify animals with radially symmetric body plans. The term Radiata is no longer accepted, as it united several different groupings of animals that do not form a monophyletic group under current views of animal phylogeny. The similarities once offered in justification of the taxon, such as radial symmetry, are now taken to be the result of either incorrect evaluations by early researchers or convergent evolution, rather than an indication of a common ancestor. Because of this, the term is used mostly in a historical context.[1]
In the early 19th century, Georges Cuvier united Ctenophora and Cnidaria in the Radiata (Zoophytes).[2] Thomas Cavalier-Smith, in 1983, redefined Radiata as a subkingdom consisting of Myxozoa, Placozoa, Cnidaria and Ctenophora.[3] Lynn Margulis and K. V. Schwartz later redefined Radiata in their Five Kingdom classification, this time including only Cnidaria and Ctenophora.[4] This definition is similar to the historical descriptor Coelenterata, which has also been proposed as a group encompassing Cnidaria and Ctenophora.[5][6]
Although radial symmetry is usually given as a defining characteristic in animals that have been classified in this group, there are clear exceptions and qualifications. Echinoderms, for example, exhibit unmistakable bilateral symmetry as larvae, and are now in the Bilateria. Ctenophores exhibit biradial or rotational symmetry, defined by tentacular and pharyngeal axes, on which two anal canals are located in two diametrically opposed quadrants.[7] Some species within the cnidarian class Anthozoa are bilaterally symmetric (For example, Nematostella vectensis). It has been suggested that bilateral symmetry may have evolved before the split between Cnidaria and Bilateria, and that the radially symmetrical cnidarians have secondarily evolved radial symmetry, meaning the bilaterality in cnidarian species like N. vectensis has a primary origin.[8]
The differing definitions assigned by zoologists are listed in the table.
Radiata or Radiates is a historical taxonomic rank that was used to classify animals with radially symmetric body plans. The term Radiata is no longer accepted, as it united several different groupings of animals that do not form a monophyletic group under current views of animal phylogeny. The similarities once offered in justification of the taxon, such as radial symmetry, are now taken to be the result of either incorrect evaluations by early researchers or convergent evolution, rather than an indication of a common ancestor. Because of this, the term is used mostly in a historical context.
In the early 19th century, Georges Cuvier united Ctenophora and Cnidaria in the Radiata (Zoophytes). Thomas Cavalier-Smith, in 1983, redefined Radiata as a subkingdom consisting of Myxozoa, Placozoa, Cnidaria and Ctenophora. Lynn Margulis and K. V. Schwartz later redefined Radiata in their Five Kingdom classification, this time including only Cnidaria and Ctenophora. This definition is similar to the historical descriptor Coelenterata, which has also been proposed as a group encompassing Cnidaria and Ctenophora.
Although radial symmetry is usually given as a defining characteristic in animals that have been classified in this group, there are clear exceptions and qualifications. Echinoderms, for example, exhibit unmistakable bilateral symmetry as larvae, and are now in the Bilateria. Ctenophores exhibit biradial or rotational symmetry, defined by tentacular and pharyngeal axes, on which two anal canals are located in two diametrically opposed quadrants. Some species within the cnidarian class Anthozoa are bilaterally symmetric (For example, Nematostella vectensis). It has been suggested that bilateral symmetry may have evolved before the split between Cnidaria and Bilateria, and that the radially symmetrical cnidarians have secondarily evolved radial symmetry, meaning the bilaterality in cnidarian species like N. vectensis has a primary origin.
The differing definitions assigned by zoologists are listed in the table.
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