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秀一篇有意思的文章“Phylogenomics Revives Traditional Views on Deep Animal Relationships”
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Quote:http://talkrational.org/showthread.php?p=443885
Quote:
| Since the days of Charles Darwin, researchers are interested in reconstructing the "Tree of Life", and in understanding the development of animal and plant species during their evolutionary history. In the case of vertebrates, this research has already come quite a long way. But there is still much debate about the relationships between the animal groups that made their apparation very early in evolutionary history, probably in the late Precambrian, some 650 to 540 million years ago. An international research group led by LMU Munich Geobiology Professor Gert Wörheide and colleagues from France and Canada has now managed to explain the relationships between some of these very early animal groups with a high degree of confidence. In the most comprehensive study of its kind, the researchers show that all sponges descended from a unique sponge ancestor, who in turn was not the ancestor of all other animals. That means that humans did not descend from a sponge-like organism either, as some scientists have put forward. Moreover, the results also suggest that the nervous system only evolved once in animal history. |
The paper and some extracts:
Quote:
| Phillipe, H. et al. (2009) Phylogenomics Revives Traditional Views on Deep Animal Relationships. Current Biology, advance online. The origin of many of the defining features of animal body plans, such as symmetry, nervous system, and the mesoderm, remains shrouded in mystery because of major uncertainty regarding the emergence order of the early branching taxa: the sponge groups, ctenophores, placozoans, cnidarians, and bilaterians. The phylogenomic approach [1] has recently provided a robust picture for intrabilaterian relationships [2,3] but not yet for more early branching metazoan clades. We have assembled a comprehensive 128 gene data set including newly generated sequence data from ctenophores, cnidarians, and all four main sponge groups. The resulting phylogeny yields two significant conclusions reviving old views that have been challenged in the molecular era: (1) that the sponges (Porifera) are monophyletic and not paraphyletic as repeatedly proposed [4,5,6,7,8,9], thus undermining the idea that ancestral metazoans had a sponge-like body plan; (2) that the most likely position for the ctenophores is together with the cnidarians in a coelenterate clade. The Porifera and the Placozoa branch basally with respect to a moderately supported eumetazoan clade containing the three taxa with nervous system and muscle cells (Cnidaria, Ctenophora, and Bilateria). This new phylogeny provides a stimulating framework for exploring the important changes that shaped the body plans of the early diverging phyla. |
http://www.cell.com/current-biology/...ge_figure=true
https://m.sciencenet.cn/blog-54593-228752.html
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