202:
1433:
954:
22:
1110:
1445:
960:
138:
traits, that has given rise to another group that has major differences from the ancestral group's condition, and is thus not considered part of the ancestral group, while still having enough similarities that we can group them under the same clade. The ancestral group will not be phylogenetically
174:' metabolism. However, the ancestors of mammals and birds also had these traits and so birds and mammals can be said to "have evolved from reptiles", making the reptiles, when defined by these traits, a grade rather than a clade. In
229:
way of defining taxa is through the use of anatomical traits. When the actual phylogenetic relationship is unknown, well defined groups sometimes turn out to be defined by traits that are primitive rather than derived. In
Linnaean
253:. Where data is lacking, or groups of uncertain relationship are to be compared, the cladistic method is limited and grade provides a useful tool for comparing organisms. This is particularly common in
344:
rather than of phylogeny. Both express the same phylogeny, but the former emphasizes the phylogenetic continuum while the latter emphasizes a distinct shift in anatomy or ecology in B relative to A.
162:
into the four familiar classes of amphibians, reptiles, birds, and mammals. In this system, reptiles are characterized by traits such as laying membranous or shelled eggs, having skin covered in
185:
Paraphyletic taxa will often, but not always, represent evolutionary grades. In some cases paraphyletic taxa are united simply by not being part of any other groups, and give rise to so-called
414:
were proposed to be the ancestors of birds as early as the 1860s. Yet the term sees popular use as an evolutionary grade excluding birds, though most scientists use a monophyletic
Dinosauria.
293:. Organizing organisms into grades rather than strict clades can also be very useful to understand the evolutionary sequence behind major diversification of both animals and plants.
261:
are often fragmentary and difficult to interpret. Thus, traditional palaeontological works are often using evolutionary grades as formal or informal taxa, including examples such as
308:
could have fatal consequences. When referring to a group of organisms, the term "grade" is usually enclosed in quotation marks to denote its status as a paraphyletic term.
300:
seeks to eliminate paraphyletic taxa, such grades are sometimes kept as formal or informal groups on the basis of their usefulness for laymen and field researchers. In
332:. The difference in approach has led to a vigorous debate between proponents of the two approaches to taxonomy, particularly in well established fields like
687:
340:. The difference between the statement "B is part of A" (phylogenetic approach) and "B has evolved from A" (evolutionary approach) is, however, one of
1476:
1048:
304:, the renaming of species or groups that turn out to be evolutionary grades is kept to a minimum to avoid misunderstanding, which in the case of
1471:
1015:
1243:
793:
Kevin de
Queiroz & Jacques Gauthier (1990). "Phylogeny as a central principle in taxonomy: phylogenetic definitions of taxon names".
866:
1203:
583:
1283:
33:), a group united by conservative anatomical and physiological traits rather than phylogeny. The flanking red and blue boxes are
1288:
1221:
1298:
1228:
1486:
1208:
1115:
1071:
1041:
752:
296:
Evolutionary grades, being united by gross morphological traits, are often eminently recognizable in the field. While
92:
118:—a diagram containing a hypothesis of relationships that reflects the evolutionary history of a group of organisms.
1398:
1324:
317:
243:
155:
771:
1449:
832:
726:
1278:
1076:
333:
249:
Where information about phylogenetic relationships is available, organisms are preferentially grouped into
1481:
1437:
1161:
1034:
878:
468:; and the last of these four groups also represents a grade, since it excludes the previous three groups.
448:, which include cellular organisms lacking a nucleus, represent a grade, since they are the ancestors of
1413:
1091:
1003:
329:
1250:
1156:
702:
131:
111:
52:
883:
1293:
1175:
639:"Primary Classification and Phylogeny of the Polemoniaceae, with Comments on Molecular Cladistics"
1216:
1086:
912:
810:
775:
718:
660:
428:. However, defining lizards by the presence of limbs is incorrect, as there are many species of
297:
218:
1007:
79:
In order to fully understand evolutionary grades, one must first get a better understanding of
16:
Non-monophyletic grouping of organisms united by morphological or physiological characteristics
1144:
1011:
904:
896:
668:
616:
579:
226:
186:
179:
115:
920:
1233:
1187:
968:
888:
847:
802:
767:
710:
650:
608:
383:
262:
239:
207:
178:, taxa that are thus seen as excluded from their evolutionary grade parent group are called
753:"Key innovations, convergence, and success: macroevolutionary lessons from plant phylogeny"
1334:
599:
Lan, R; Reeves, PR (2002). "Escherichia coli in disguise: molecular origins of
Shigella".
429:
361:
290:
163:
499:
Likewise, apes represent a grade in common usage, but are a clade if humans are included.
706:
201:
25:
Cladogram (family tree) of a biological group. The green box (central) may represent an
1308:
992:
892:
369:
235:
972:
612:
556:
Familles naturelles du règne animal, exposés succinctement et dans un ordre analytique
1465:
1303:
1273:
1180:
1057:
851:
828:
529:
254:
80:
68:
60:
56:
916:
779:
722:
1408:
1354:
1349:
1344:
1329:
1137:
1132:
936:
425:
373:
325:
301:
175:
171:
420:
represent an evolutionary grade, defined by their retention of limbs relative to
1403:
1096:
571:
439:
435:
231:
1105:
1081:
976:
953:
471:
445:
379:
282:
278:
135:
107:
900:
1418:
1382:
1377:
1372:
1267:
1149:
449:
341:
286:
190:
144:
127:
96:
84:
40:
30:
21:
961:
Further
Evidence of the Affinity between the Dinosaurian Reptiles and Birds
908:
672:
620:
1109:
475:
411:
397:
393:
357:
305:
274:
270:
159:
151:
88:
688:"Poriferan paraphyly and its implications for Precambrian palaeobiology"
328:
taxa are recognized. This differs from the more traditional approach of
999:
814:
664:
465:
405:
387:
365:
266:
246:
evolutionary grades (or any other form of paraphyly) are not accepted.
104:
714:
485:
479:
453:
417:
337:
258:
250:
167:
867:"Stems, nodes, crown clades, and rank-free lists: is Linnaeus dead?"
806:
655:
638:
1238:
1166:
493:
461:
457:
421:
401:
324:
has come under debate. Under a strict phylogenetic approach, only
321:
200:
140:
64:
35:
1026:
353:
213:
1030:
686:
Sperling, E. A.; Pisani, D.; Peterson, K. J. (1 January 2007).
994:
Their Blood Runs Cold: Adventures With
Reptiles and Amphibians
489:
386:) represent a grade, since they are also the ancestors of the
100:
356:
represent a grade, in as much as they have given rise to the
772:
10.1666/0094-8373(2005)031[0077:KICASM]2.0.CO;2
488:
represent a grade, since they include the ancestors of
965:
Quarterly
Journal of the Geological Society of London
515:
Huxley J. 1959. Clades and grades. In Cain A.J. (ed)
59:
complexity. The term was coined by
British biologist
87:
history and relationships among or within groups of
1391:
1365:
1317:
1259:
1196:
1125:
1064:
474:represent a grade, since they are the ancestors of
438:represent a grade, since they are the ancestors of
154:. In the early 19th century, the French naturalist
991:
695:Geological Society, London, Special Publications
396:represent a grade composed of the cold-blooded
382:in the biological sense (including the extinct
943:5th ed. Saunders, Philadelphia. (6th ed. 1985)
1042:
990:Gibbons, J. Whitfield; Gibbons, Whit (1983).
234:, evolutionary grades are accepted in higher
8:
833:"Classifications and other ordering systems"
632:
630:
320:, the use of evolutionary grades as formal
150:The most commonly cited example is that of
1049:
1035:
1027:
882:
654:
601:Microbes and Infection / Institut Pasteur
552:Nouveau Dictionnaire à Histoire Naturelle
932:
930:
554:, xxiv; cited in Latreille, P.A. (1825).
289:and many of the more well known taxa of
91:. These relationships are determined by
20:
566:
564:
508:
130:grade is a group of species united by
114:. The result of such an analysis is a
7:
1444:
751:Donoghue, Michael J. (1 June 2005).
432:, which are considered true lizards.
376:) all represent evolutionary grades.
312:Grades and phylogenetic nomenclature
122:Definition of an evolutionary grade
893:10.1111/j.1469-185X.2000.tb00055.x
519:. Systematics Association, London.
14:
973:10.1144/GSL.JGS.1870.026.01-02.08
517:Function and taxonomic importance
360:. In turn, the three traditional
1477:Evolutionary biology terminology
1443:
1432:
1431:
1284:Phylogenetic comparative methods
1108:
967:. Vol. 26. pp. 12–31.
952:
852:10.1046/j.1439-0469.2002.00211.x
51:is a taxon united by a level of
1289:Phylogenetic niche conservatism
95:methods that focus on observed
238:, though generally avoided at
1:
1472:Evolutionary biology concepts
840:J. Zool. Syst. Evol. Research
613:10.1016/S1286-4579(02)01637-4
939:. & T.S. Parsons. 1977.
1209:Phylogenetic reconciliation
1116:Evolutionary biology portal
1072:Computational phylogenetics
959:Huxley, Thomas H. (1870). "
578:. Oxford University Press.
143:), and so will represent a
1503:
643:American Journal of Botany
1427:
1399:Phylogenetic nomenclature
1103:
831:& Bock, W.J. (2002).
318:phylogenetic nomenclature
244:phylogenetic nomenclature
217:, yet actively in use in
550:Latreille, P.A. (1804).
334:vertebrate palaeontology
158:was the first to divide
139:complete (i.e. is not a
1279:Molecular phylogenetics
1229:Distance-matrix methods
1077:Molecular phylogenetics
1299:Phylogenetics software
1213:Probabilistic methods
1162:Long branch attraction
865:Benton, M. J. (2000).
222:
93:phylogenetic inference
44:
1092:Evolutionary taxonomy
1004:University of Alabama
637:Grant, Verne (1998).
330:evolutionary taxonomy
204:
197:Grades in systematics
24:
1251:Three-taxon analysis
1157:Phylogenetic network
941:The Vertebrate Body.
242:level and below. In
1294:Phylogenetic signal
707:2007GSLSP.286..355S
576:The Variety of Life
83:: the study of the
63:, to contrast with
1487:Taxonomy (biology)
1222:Bayesian inference
1217:Maximum likelihood
871:Biological Reviews
223:
219:palaeoanthropology
189:which may even be
45:
27:evolutionary grade
1459:
1458:
1204:Maximum parsimony
1197:Inference methods
1145:Phylogenetic tree
1017:978-0-8173-0135-4
482:and related taxa.
478:, which includes
452:, which includes
316:With the rise of
116:phylogenetic tree
1494:
1447:
1446:
1435:
1434:
1234:Neighbor-joining
1188:Ghost population
1118:
1113:
1112:
1051:
1044:
1037:
1028:
1022:
1021:
1006:Press. pp.
997:
987:
981:
980:
956:
950:
944:
934:
925:
924:
919:. Archived from
886:
862:
856:
855:
837:
825:
819:
818:
790:
784:
783:
757:
748:
742:
741:
739:
737:
731:
725:. Archived from
715:10.1144/SP286.25
692:
683:
677:
676:
658:
634:
625:
624:
596:
590:
589:
568:
559:
548:
542:
541:
539:
537:
532:. Biology online
526:
520:
513:
400:; this excludes
358:land vertebrates
225:The traditional
211:is ancestral to
208:Australopithecus
187:wastebasket taxa
180:taxa in disguise
170:, and having a '
99:traits, such as
39:(i.e., complete
1502:
1501:
1497:
1496:
1495:
1493:
1492:
1491:
1462:
1461:
1460:
1455:
1423:
1387:
1361:
1335:Symplesiomorphy
1313:
1255:
1192:
1121:
1114:
1107:
1101:
1065:Relevant fields
1060:
1055:
1025:
1018:
989:
988:
984:
958:
951:
947:
935:
928:
923:on 5 June 2011.
884:10.1.1.573.4518
864:
863:
859:
835:
827:
826:
822:
807:10.2307/2992353
792:
791:
787:
755:
750:
749:
745:
735:
733:
729:
690:
685:
684:
680:
656:10.2307/2446408
636:
635:
628:
607:(11): 1125–32.
598:
597:
593:
586:
570:
569:
562:
549:
545:
535:
533:
528:
527:
523:
514:
510:
506:
430:legless lizards
384:Labyrinthodonts
350:
314:
291:human evolution
263:labyrinthodonts
236:taxonomic ranks
199:
124:
77:
17:
12:
11:
5:
1500:
1498:
1490:
1489:
1484:
1479:
1474:
1464:
1463:
1457:
1456:
1454:
1453:
1441:
1428:
1425:
1424:
1422:
1421:
1416:
1411:
1406:
1401:
1395:
1393:
1389:
1388:
1386:
1385:
1380:
1375:
1369:
1367:
1363:
1362:
1360:
1359:
1358:
1357:
1352:
1347:
1339:
1338:
1337:
1332:
1321:
1319:
1315:
1314:
1312:
1311:
1309:Phylogeography
1306:
1301:
1296:
1291:
1286:
1281:
1276:
1271:
1263:
1261:
1260:Current topics
1257:
1256:
1254:
1253:
1248:
1247:
1246:
1241:
1236:
1226:
1225:
1224:
1219:
1211:
1206:
1200:
1198:
1194:
1193:
1191:
1190:
1185:
1184:
1183:
1173:
1164:
1159:
1154:
1153:
1152:
1142:
1141:
1140:
1129:
1127:
1126:Basic concepts
1123:
1122:
1120:
1119:
1104:
1102:
1100:
1099:
1094:
1089:
1084:
1079:
1074:
1068:
1066:
1062:
1061:
1056:
1054:
1053:
1046:
1039:
1031:
1024:
1023:
1016:
982:
945:
926:
877:(4): 633–648.
857:
820:
801:(4): 307–322.
785:
766:(sp5): 77–93.
743:
701:(1): 355–368.
678:
649:(6): 741–752.
626:
591:
584:
560:
543:
521:
507:
505:
502:
501:
500:
497:
483:
469:
443:
433:
426:amphisbaenians
415:
409:
391:
377:
370:Chondrichthyes
349:
346:
313:
310:
198:
195:
123:
120:
110:sequences, or
76:
73:
15:
13:
10:
9:
6:
4:
3:
2:
1499:
1488:
1485:
1483:
1482:Obsolete taxa
1480:
1478:
1475:
1473:
1470:
1469:
1467:
1452:
1451:
1442:
1440:
1439:
1430:
1429:
1426:
1420:
1417:
1415:
1412:
1410:
1407:
1405:
1402:
1400:
1397:
1396:
1394:
1390:
1384:
1381:
1379:
1376:
1374:
1371:
1370:
1368:
1364:
1356:
1353:
1351:
1348:
1346:
1343:
1342:
1340:
1336:
1333:
1331:
1328:
1327:
1326:
1323:
1322:
1320:
1316:
1310:
1307:
1305:
1304:Phylogenomics
1302:
1300:
1297:
1295:
1292:
1290:
1287:
1285:
1282:
1280:
1277:
1275:
1274:DNA barcoding
1272:
1270:
1269:
1265:
1264:
1262:
1258:
1252:
1249:
1245:
1244:Least squares
1242:
1240:
1237:
1235:
1232:
1231:
1230:
1227:
1223:
1220:
1218:
1215:
1214:
1212:
1210:
1207:
1205:
1202:
1201:
1199:
1195:
1189:
1186:
1182:
1181:Ghost lineage
1179:
1178:
1177:
1174:
1172:
1168:
1165:
1163:
1160:
1158:
1155:
1151:
1148:
1147:
1146:
1143:
1139:
1136:
1135:
1134:
1131:
1130:
1128:
1124:
1117:
1111:
1106:
1098:
1095:
1093:
1090:
1088:
1085:
1083:
1080:
1078:
1075:
1073:
1070:
1069:
1067:
1063:
1059:
1058:Phylogenetics
1052:
1047:
1045:
1040:
1038:
1033:
1032:
1029:
1019:
1013:
1009:
1005:
1001:
996:
995:
986:
983:
978:
974:
970:
966:
962:
955:
949:
946:
942:
938:
933:
931:
927:
922:
918:
914:
910:
906:
902:
898:
894:
890:
885:
880:
876:
872:
868:
861:
858:
853:
849:
846:(4): 169–94.
845:
841:
834:
830:
824:
821:
816:
812:
808:
804:
800:
796:
789:
786:
781:
777:
773:
769:
765:
761:
754:
747:
744:
732:on 9 May 2009
728:
724:
720:
716:
712:
708:
704:
700:
696:
689:
682:
679:
674:
670:
666:
662:
657:
652:
648:
644:
640:
633:
631:
627:
622:
618:
614:
610:
606:
602:
595:
592:
587:
585:0-19-860426-2
581:
577:
573:
567:
565:
561:
557:
553:
547:
544:
531:
525:
522:
518:
512:
509:
503:
498:
495:
491:
487:
484:
481:
477:
473:
470:
467:
463:
459:
455:
451:
447:
444:
441:
437:
434:
431:
427:
423:
419:
416:
413:
410:
407:
403:
399:
395:
392:
389:
385:
381:
378:
375:
371:
367:
363:
359:
355:
352:
351:
347:
345:
343:
339:
335:
331:
327:
323:
319:
311:
309:
307:
303:
299:
294:
292:
288:
284:
280:
276:
272:
268:
264:
260:
256:
255:palaeontology
252:
247:
245:
241:
237:
233:
228:
220:
216:
215:
210:
209:
203:
196:
194:
192:
188:
183:
181:
177:
173:
169:
165:
161:
157:
153:
148:
146:
142:
137:
136:physiological
133:
132:morphological
129:
121:
119:
117:
113:
109:
106:
102:
98:
94:
90:
86:
82:
81:phylogenetics
75:Phylogenetics
74:
72:
70:
67:, a strictly
66:
62:
61:Julian Huxley
58:
57:physiological
54:
53:morphological
50:
42:
38:
37:
32:
28:
23:
19:
1448:
1436:
1409:Sister group
1392:Nomenclature
1355:Autapomorphy
1350:Synapomorphy
1330:Plesiomorphy
1318:Group traits
1266:
1170:
1138:Cladogenesis
1133:Phylogenesis
993:
985:
975:– via
964:
948:
940:
921:the original
874:
870:
860:
843:
839:
823:
798:
794:
788:
763:
760:Paleobiology
759:
746:
734:. Retrieved
727:the original
698:
694:
681:
646:
642:
604:
600:
594:
575:
572:Tudge, Colin
555:
551:
546:
534:. Retrieved
524:
516:
511:
374:Osteichthyes
326:monophyletic
315:
302:bacteriology
295:
248:
224:
212:
206:
191:polyphyletic
184:
176:microbiology
172:cold-blooded
149:
145:paraphyletic
128:evolutionary
125:
85:evolutionary
78:
69:phylogenetic
48:
46:
41:monophyletic
34:
31:paraphyletic
26:
18:
1404:Crown group
1366:Group types
1097:Systematics
829:Mayr, Ernst
536:15 February
530:"phylogeny"
492:(including
472:Crustaceans
446:Prokaryotes
440:land plants
436:Green algae
287:lobopodians
283:eurypterids
232:systematics
103:sequences,
1466:Categories
1082:Cladistics
977:Wikisource
937:Romer, A.S
795:Syst. Zool
504:References
450:eukaryotes
380:Amphibians
205:The genus
112:morphology
108:amino acid
43:subtrees).
1419:Supertree
1383:Polyphyly
1378:Paraphyly
1373:Monophyly
1345:Apomorphy
1325:Primitive
1268:PhyloCode
1150:Cladogram
901:0006-3231
879:CiteSeerX
736:22 August
412:Dinosaurs
364:of fish (
342:semantics
306:pathogens
279:ammonites
275:dinosaurs
271:synapsids
160:tetrapods
156:Latreille
97:heritable
89:organisms
1438:Category
1341:Derived
1087:Taxonomy
917:17851383
909:11117201
780:36988476
723:34175521
673:21684957
621:12361912
574:(2000).
476:hexapods
466:protists
398:amniotes
394:Reptiles
388:amniotes
348:Examples
298:taxonomy
267:anapsids
257:, where
227:Linnaean
152:reptiles
1450:Commons
1176:Lineage
1000:Alabama
815:2992353
703:Bibcode
665:2446408
486:Monkeys
480:insects
454:animals
418:Lizards
406:mammals
366:Agnatha
362:classes
259:fossils
147:taxon.
105:protein
1014:
957:
915:
907:
899:
881:
813:
778:
721:
671:
663:
619:
582:
494:humans
464:, and
458:plants
422:snakes
338:botany
251:clades
240:family
168:scutes
164:scales
71:unit.
36:clades
1414:Basal
1239:UPGMA
1171:Grade
1167:Clade
913:S2CID
836:(PDF)
811:JSTOR
776:S2CID
756:(PDF)
730:(PDF)
719:S2CID
691:(PDF)
661:JSTOR
462:fungi
402:birds
141:clade
65:clade
49:grade
1012:ISBN
905:PMID
897:ISSN
738:2012
669:PMID
617:PMID
580:ISBN
538:2013
490:apes
424:and
404:and
372:and
354:Fish
336:and
322:taxa
214:Homo
1169:vs
1008:164
969:doi
963:".
889:doi
848:doi
803:doi
768:doi
711:doi
699:286
651:doi
609:doi
166:or
134:or
126:An
101:DNA
55:or
1468::
1010:.
1002::
998:.
929:^
911:.
903:.
895:.
887:.
875:75
873:.
869:.
844:40
842:.
838:.
809:.
799:39
797:.
774:.
764:31
762:.
758:.
717:.
709:.
697:.
693:.
667:.
659:.
647:85
645:.
641:.
629:^
615:.
603:.
563:^
496:).
460:,
456:,
368:,
285:,
281:,
277:,
273:,
269:,
265:,
193:.
182:.
47:A
1050:e
1043:t
1036:v
1020:.
979:.
971::
891::
854:.
850::
817:.
805::
782:.
770::
740:.
713::
705::
675:.
653::
623:.
611::
605:4
588:.
558:.
540:.
442:.
408:.
390:.
221:.
29:(
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
