Deuterostomes - Deuterostomes Superb Fairy-wren, Malurus...

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Deuterostomes Superb Fairy-wren , Malurus cyaneus Deuterostomes differ from the other Bilateria, called protostomes , in several ways. In both cases there is a complete digestive tract. However, in protostomes, the first opening of the gut to appear in embryological development (the archenteron ) develops into the mouth, with the anus forming secondarily. In deuterostomes the anus forms first, with the mouth developing secondarily. [61] In most protostomes, cells simply fill in the interior of the gastrula to form the mesoderm, called schizocoelous development, but in deuterostomes, it forms through invagination of the endoderm, called enterocoelic pouching. [62] Deuterostome embryos undergo radial cleavage during cell division, while protostomes undergo spiral cleavage. [63]
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All this suggests the deuterostomes and protostomes are separate, monophyletic lineages. The main phyla of deuterostomes are the Echinodermata and Chordata . [64] The former are radially symmetric and exclusively marine, such as starfish , sea urchins , and sea cucumbers . [65] The latter are dominated by the vertebrates , animals with backbones. [66] These include fish , amphibians , reptiles , birds , and mammals . [67] In addition to these, the deuterostomes also include the Hemichordata , or acorn worms. [68] Although they are not especially prominent today, the important fossil graptolites may belong to this group. [69] The Chaetognatha or arrow worms may also be deuterostomes, but more recent studies suggest protostome affinities. Ecdysozoa
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Yellow-winged darter , Sympetrum flaveolum The Ecdysozoa are protostomes, named after the common trait of growth by moulting or ecdysis . [70]
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This note was uploaded on 03/26/2012 for the course SCIENCE 103 taught by Professor Na during the Spring '12 term at American International.

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Deuterostomes - Deuterostomes Superb Fairy-wren, Malurus...

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