Pentamerous Radial Symmetry – Echinoderm Adults only Earlandħ Tissue Layers Endoderm - digestion and respiration structures A notable exception to the trend of cephalization throughout evolutionary advancement is phylum Echinodermata, which have Pentamerous Radial Symmetry – Echinoderm Adults onlyĦ Symmetry None – Porifera Radial – Cnidaria Bilateral – All others This process is also tied to the development of an anterior brain in the chordates from the notochord. In addition to a concentration of sense organs, all animals from annelids on also place the mouth in the head region. It accompanied the move to bilateral symmetry made in flatworms, with ocelli and pinnae placed in the head region. Cephalization is intrinsically connected with a change in symmetry. This process eventually produces a head region with sensory organs. No cell walls TWO MAIN DIVISIONS: Invertebrate: all other phyla without internal skeletons Vertebrate: Phylum Chordate – internal skeletonĤ Level of Organization Cellular – Porifera Tissues – Cnidariaĥ Cephalization Cephalization is considered an evolutionary trend, whereby nervous tissue, over many generations, becomes concentrated toward one end of an organism. Eukaryotic: animal cells with a nucleus and organelles – large diversity of cell specialization 4. 1 Kingdom Animalia The Big Picture EarlandĭEFINING CHARACTERISTCS OF ANIMALS 1.
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