Endoskeleton three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera, and Coleoidea. An endoskeleton may function purely for support (as in the case of sponges), but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; there, a mollusk exoskeleton evolved into several sorts of internal
Branching order of bacterial phyla (Cavalier-Smith, 2002) with peptidoglycan, while Archaea and Eukaryotes stem from Actinobacteria. Branching order of bacterial phyla (Cavalier-Smith, 2002) There are several models of the Branching order of bacterial phyla, one of these was proposed in 2002 and 2004 by Thomas Cavalier-Smith. In this frame of work, the branching order of the major lineage of bacteria are determined based on some morphological characters, such as cell wall structure, and not based on the molecular evidence (molecular phylogeny). Whereas modern molecular studies point towards the root of the tree of life being between a monophyletic Bacteria and Archaea+Eukarya (Neomura), in the Cavalier-Smith theory, the