Before the Backbone: Views on the origin of the vertebratesWe cannot catechise our stony ichthyolites, as did the necromantic lady of the Arabian Nights did the coloured fishes of the lake which had once been a city, when she touched their dead bodies with her wand, and they straightaway raised their heads and rephed to her queries. We would have many a question to ask them if we could - questions never to be solved. Hugh Miller, The Old Red Sandstone When I started this book in 1991, the subject of vertebrate origins was fusty and unfashionable. Early drafts for this preface read like an extend ed complaint at the lot of traditional morphologists, cast aside by the march of modern molecular biology. But no longer - this book should reach you at a time of renewed inter est in the origin of the vertebrates, our own particular corner of creation. For although the topic has excited interest for well over a century, molec ular biology has only lately achieved the maturity necessary to test its predictions. As a legitimate field of study, it is fashionable again. |
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Page xv
... common ancestry . In any analysis beyond the trivial , the number of possible clado- grams generated by a given set of organisms and features is often very large , and convention selects as the provisional solution that which keeps the ...
... common ancestry . In any analysis beyond the trivial , the number of possible clado- grams generated by a given set of organisms and features is often very large , and convention selects as the provisional solution that which keeps the ...
Page 4
... common descent . The latest common ancestor of all metazoans is pre- sumed to have had these same features . A group such as the metazoans , in which qualification for membership depends on shared common ancestry , is called ...
... common descent . The latest common ancestor of all metazoans is pre- sumed to have had these same features . A group such as the metazoans , in which qualification for membership depends on shared common ancestry , is called ...
Page 8
... common ancestry , and did not appear independently in several groups . These features are : the fate of the blastopore ( protostomy or deuterostomy ) ; the style of cleavage in the early embryo ( spiral or radial ) ; • the fate of ...
... common ancestry , and did not appear independently in several groups . These features are : the fate of the blastopore ( protostomy or deuterostomy ) ; the style of cleavage in the early embryo ( spiral or radial ) ; • the fate of ...
Page 9
... common solu- tion to a problem of functional design . In spiral cleavage , the embryo is formed of tiers of cells such that the cells in each are offset by a small amount from those above and below . In the same way that offsets between ...
... common solu- tion to a problem of functional design . In spiral cleavage , the embryo is formed of tiers of cells such that the cells in each are offset by a small amount from those above and below . In the same way that offsets between ...
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... common ancestry ( Figure 1.4 ) . What was this ancestor like ? It is fair to assume that it resembled a flat- worm , a basic , no - frills bilaterally symmetrical triploblast without any extras such as a coelom , segmentation , anus and ...
... common ancestry ( Figure 1.4 ) . What was this ancestor like ? It is fair to assume that it resembled a flat- worm , a basic , no - frills bilaterally symmetrical triploblast without any extras such as a coelom , segmentation , anus and ...
Contents
The origins of vertebrates | 84 |
Head to head | 160 |
Jefferies Calcichordate Theory | 201 |
Conclusions | 287 |
References | 305 |
Index | 337 |
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Common terms and phrases
adult amphioxus anatomy ancestor ancestry animal annelids anus appendage arthropods ascidians Berrill Berrill's bilateral body brain branchial brates calcichordate calcichordate theory calcite calcite skeleton Cambrian carpoids cells cephalochordates Cephalodiscus Ceratocystis chordates ciliated cladistics cluster coelom conodont cornutes and mitrates Cothurnocystis craniates creatures crinoids deuterostomes dexiothetism dorsal Drosophila echinoderms embryo endostyle enteropneusts evidence evolution evolutionary evolved expression Figure fossil function Garstang Gaskell Gaskell's genetic gill slits Gislén hagfishes head hemichordates Holland homeobox genes homologous Hox genes hydrocoel ideas interpretation Jefferies Lagynocystis lampreys larva lophophore mesoderm metazoan modern molecular morphological mouth muscles neoteny nerve cord nervous system neural crest notochord ontogeny Ordovician organs origin of vertebrates paedomorphosis pharynx phylogenetic phylogeny plates posterior primitive protostomes pterobranchs recapitulation reconstruction segmentation sessile somatocoel somites species stele stem structures suggests symmetry tadpole larva tail theca tion tissue tunicate tadpole urochordates ventral verte vertebrate origins vertebrates visceral water-vascular system
Popular passages
Page 160 - Fillet of a fenny snake, In the cauldron boil and bake ; Eye of newt and toe of frog, Wool of bat and tongue of dog...
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