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Classification of animals, The important characteristic features of the different phyla under non-chordates are, described as follows:, , Phylum Porifera, 1. Members of this phylum are commonly known as sponges which are referred to as, pore bearers'., 2. All sponges are aquatic, mostly marine, rarely fresh water, sessile., 3. Most of the sponges are asymmetrical. Some are radially symmetrical., 4. The sponges are the first multicellular diploblastic animals., , 5. The sponges have cellular level of organization., 6. Sponges have a water transport or canal system. Water enters through minute, central cavity, spongocoel, from where it goes out through the osculum., 7. Choanocytes or collar cells line the spongocoel and the canals., , 8. Digestion is intracellular and takes place inside food vacuoles., 9. Almost all sponges possess an internal skeleton. It may consist of calcareous or, siliceous spicules or of fine sponging fibres., 10. Sponges are hermaphrodite. Eg. eggs and sperms are produced by the same, individual. Sponges reproduce asexually by fragmentation and sexually by formation, of gametes., 11. Fertilization is internal and development is indirect having a larval stage which is, , morphologically distinct from the adult including free swimming amphiblastula (in, Sycon) and parenchymula (in Leucosolenio) larvae., 12. Eg, Sycon (Scypha), Spongilla (Freshwater sponge) and Euspongia (Bath sponge)., , Three types of canal system are found in sponges:, Ascon type is the simplest type ofcanal system, e.g, Leucosolenia., Sycon type is more complex than the ascon type, e.g., Sycon., Leucon type is most complex canal system, e.g, Spongilla., , Fig: Examples of Porifera (a) Sycon; (b} Euspongio; (c) Spongilla

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Phylum Coelenterata (Cnidaria), 1. All are aquatic and are mostly marine, except a few like Hydro, are fresh water,, , sessile or free swimming., 2. They show radial symmetry., , 3. Cnidarians are diploblastic animals., 4. They show tissue level organization., 5. The name Cnidaria is derived from the cnidoblasts or cnidocytes (which contain the, stinging capsules or nematocysts) present on the tentacles and the body., Cnidoblasts are present in epidermis and are used for anchorage, defense and for, , the capture of prey., , Nameato, , Nucieus, , Figure, , 4.7, , Cnidoblast, , 6. Statocyst, a sense organ for balance, is developed for first time in Cnidaria., 7. They have a central gastrovascular cavity with a single opening, mouth on, , hypostome., 8. Digestion is both extracellular and intracellular., 9. Some of the cnidarians like corals have a skeleton composed of calcium carbonate., 10. They exhibit two basic body forms called polyp and medusa. The former is a sessile, and cylindrical form like Hydro, Adamsia, etc., whereas, the latter is umbrella-shaped, and free swimming like Aurelia or jellyfish., 11. Cnidarians which exist in both forms exhibit alternation of generation, (metagenesis), i.e., polyps produce medusae asexually and medusae from the polyps, sexually e.g, Obelia., , 12. E.g. Physalia, Adamsia (Sea anemone), Pennatula (Sea-pen), Gorgonia (Sea-fan) and, Meandrina (Brain coral)., , Aurelia (Medusa form), , Adamsia (Polyp form), , Fig.: Examples of Coelenterata (a) Aurelio; (b) Adamsio

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Phylum Ctenophora, 1. Commonly known as comb jellies., , 2. They are exclusively marine, radially symmetrical, diploblastic organisms,, Acoelomates with tissue level of organization., 3. The body bears eight external rows of ciliated comb plates, which help in, , locomotion., 4. Ctenophores show bioluminescence, the property of living organisms to emit light., 5. Special adhesive and sensory cells, called colloblasts or lasso cells are present on, tentacles for capturing food and, 6. Digestive tract is complete. Digestion is both extracellular and intracellular., , prey, , Skeleton, circulatory, respiratory and excretory systems are absent., 8. Sexes are not separate., 9., , Reproduction takes place only by sexual means, , 10. Fertilization is external with indirect development, 11. E.g, Pleurobrachia and Ctenoplana., Pear or walnut, , shaped body, Aboral surface, , Tentacles, , Ciliated comb plates, , Fig.: Example of Ctenophora (Pleurobrachia)

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Phylum Platyhelminthes, 1. They have dorsoventraly flattened body, hence are called flatworms., 2. These are mostly endoparasites found in animals including human beings., 3., , Flatworms are bilaterally symmetrical, triploblastic and Acoelomate animals with, organ level of organisation., , 4. Digestive system is incomplete due to presence of only one opening, even reduced, , or absent in parasitic forms., 5., , Hooks and suckers are present in the parasitic forms. Some of them absorb nutrients, , from the host directly through their body surface., 6. Specialised cells called flame cells help in osmoregulation and excretion., , Tape worm, , Liverfluke, , 7. They have a bilateral nervous system. Two cord-like nerves branch repeatedly in an, array resembling a ladder., , 8. The head end of some species even has a collection of ganglia acting as a, , rudimentary brain to integrate signals from sensory organs such as eyespots., 9. Sexes are not separate., , 10. Fertilization is internal and development is through many larval stages., , 11. Some members like Planaria possess high regeneration capacity., 12. E.g., Toenia (Tapeworm), Fasciola (Liver fluke)., , Phylum Aschelminthes, 1. The body of the aschelminthes is circular in cross-section, hence, the name, , roundworms., 2. They may be free-living, aquatic and terrestrial or parasitic in plants and animals., , 3. Round worms have organ system level of body organisation., 4. They are bilaterally symmetrical, triploblastic and pseudocoelomate animals., 5., , Sense organs Include () Papllae- tactile in function; (i) Amphids - chemoreceptors;, , Ci) Phasmids-glandulosensory in, 6., , nature., Indirect development includes following lanval stages- filariform larva in, , Ancylostoma, microfilaria larva, Enterobius., , in Wuchereria and rhabditiform larva in Ascaris and

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7. Body wall consists of non-living, resistant cuticle, syncytial epidermis and muscle, , layer., , Male, , Female, , Aschelminthes-Roundworm, 8. Allmentary canal is complete with a well developed muscular pharynx., 9. An excretory tube removes body wastes from the body cavity through the excretory, pore., , 10. Sexes are separate i.e., males and females are distinct. Often females are longer than, males., , 11. Fertilization is internal and development may be direct or indirect., , 12. E.g, Ascaris, Wuchererio, Ancylostoma.