http://en.wikipedia.org/wiki/Animal
The sponges (Porifera) were long thought to have diverged from other animals early.They lack the complex organization found in most other phyla.Their cells are differentiated, but in most cases not organized into distinct tissues.Sponges typically feed by drawing in water through pores.Archaeocyatha, which have fused skeletons, may represent sponges or a separate phylum.However, a phylogenomic study in 2008 of 150 genes in 29 animals across 21 phyla revealed that it is the Ctenophora or comb jellies which are the basal lineage of animals, at least among those 21 phyla. The authors speculate that sponges—or at least those lines of sponges they investigated—are not so primitive, but may instead be secondarily simplified.
The sponges (Porifera) were long thought to have diverged from other animals early.They lack the complex organization found in most other phyla.Their cells are differentiated, but in most cases not organized into distinct tissues.Sponges typically feed by drawing in water through pores.Archaeocyatha, which have fused skeletons, may represent sponges or a separate phylum.However, a phylogenomic study in 2008 of 150 genes in 29 animals across 21 phyla revealed that it is the Ctenophora or comb jellies which are the basal lineage of animals, at least among those 21 phyla. The authors speculate that sponges—or at least those lines of sponges they investigated—are not so primitive, but may instead be secondarily simplified.
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