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Phylum-Cnidaria By Juhi Mishra
TARGET AUDIENCE All biology aspirants for any competitive exam
This is Juhi Mishra * M.Sc.in Botany(Gold Medalist) 7 years of Teaching Experience CET, DCA & B.Ed in Biology
Phylum Cnidaria/Coelenterata: General Characteristic and Classification
General characteristics of Phylum Coelenterata 1. Kingdom: Animalia 2. Habitat: aquatic, mostly marine 3. Habit: solitary or colonial. Each individual is known as zooid 4. Symmetry: radially symmetrical 5. Grade of organization: tissue grade of organization
6. Germ layer: diploblastic, outer ectoderm and inner endoderm Mesogloea separates these two layer 7. The body has a single opening called hypostome urrounded by sensor y tentacles. 8. Coelom: gastrovascular cavity or coelenteron.
9. Nematocyst: organ for capturing and paralyzing pray, present in tentacles 0. Nutrition: holozoic 1. Digestion is both intracellular and extracellular. 2. Respiration and excretion are accomplished by simple diffusion. 3. Circulatory system: absent
4. Nervous system: poorly develop 5. Many forms exhibit polymorphism ie Polyp and medusa 6. Polyps are sessile, asexual stage 7. Medusa are free swimming, sexual stage 8. Metagenesis: asexual polypoid generation alternate with sexual medusoid generation
Mouth/anus Tentacle Gastrovascular cavity - Gastrodermis Mesoglea Epidermis Body stalk Gastrovascular cavity Gastrodermis Mesoglea Epidermis Tentacle Mouth/anus
9. Reproduction: - Asexual: by budding - Sexual: by gamatic fusion :0. Fertilization: internal or external 1. Development: indirect with larval stage 2. (Koilos: hollow, enteron: cavity)
mouth tentacle epitheliomuscular gastrovascular cavity gastrodermis mesoglea epidermis mesoglea gastrodermis mesorislongitudinal muscle fibers cnidocyte sensory interstitial nerve net gastrovascular cavity Ecell epidermis Circular muscle fibers Cross section of Hydra
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