It also may imply as the film suggest that sponges have lost systems and become more simple. This would put both Porifera and Cnidaria as very long branches, living representatives very derived and looking very different than the ancestors that gave rise to them. However contrast this with the view presented in the film that Ctenophores share more in common with other metazoans than sponges or cnidarians based on new molecular data. According to this views sponges and Eumetazoa are sister groups with Porifera splitting off well before Cnidaria. Molecular evidence suggests sponges do share a common ancestor with other animals. Molecular rRNA coding evidence suggests a common ancestor for choanoflagellates and metazoans. Sponges appear in the fossil record before the Cambrian. Scientists are studying colony formation and cell-to-cell communication in choanoflagellates in search of clues to the evolution of multicellularity. They are characterized by possession of a flagella that is surrounded by a collar.Ĭhoanoflagellates resemble sponge feeding cells (choanocytes). Many biologists feel that because of their similarity to certain cells found in sponges that Choanoflagellates, a group of protists that can be solitary or colonial, are the most likely group to have given rise to metazoans. Multicellular animals are called metazoans. Good summary of newer research on sponges īackground on understanding old and new phylogenetic relationships of sponges. Evolution of the eukaryotic cell was followed by diversification into many lineages including, modern protozoans, plants, fungi, and animals.
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