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ZOO-MJ-T-101 (Taxonomy and Introduction to Non-chordates) Module 4: Cnidaria (L1) Phylum Cnidaria is also known as Phylum Coelenterate. The term “cnidaria” is derived from the Greek word “cnidos,” which means “stinging thread.” They are characterized by stinging cells called Cnidoblast and a cavity called coelenterates, justifying the name Cnidaria or Coelenterata. > General characteristics of Phylum Cnidaria: Question: Discuss a) Habitat: pm is These are mostly marine and a few like hydra live in fresh water " a Question: Write de two salient features the phylum cnidaria. KU-2023) b) Habit: They are solitary or conical and Sedentary or free-swimming. c) Grade of organization: Body organization of cell-tissue grade. Cells mostly scattered and specialized for different functions. Some cells form tissues like nerve nets or nervous tissues. Question: Clas: Phylum Cnidaria u subclass. State tl salient feature v example. (344, k 2021, GE-01) d) Shape: They show polymorphism i.e, two body forms are present: asexual polyp and sexual medusa stage. Polyp is in cylindrical shape and medusae is umbrella-shaped. : e) Symmetry: Individuals are radially or biradially symmetrical in a longitudinal oral-aboral axis. f) Germ layer: They are diploblastic animals with 2 cellular layers: outer an epidermis and an inner gastrodermis- with a gelatinous acellular mesoglea in between. 2) Locomotion: Two types of individuals occur, attached sessile and asexual zooid (polyps) and free swimming and sexual zooid (medusae). h) Digestion: They show both intracellular and extracellular digestion in the gastrovascular cavity. i) Nervous system: They have a poorly developed nervous system and it is present in the form of a nerve net in the body walls and the tentacles. Besides nerve nets, medusae have nerve rings and ganglia around the margin of the bell. Nerve impulse can travel in any direction. j) Circulatory, respiration and excretion: Circulatory, respiratory and excretory systems are absent in Cnidarians. Gaseous exchange and excretion take place through the body surface. 
