Animal Kingdom - Notes | Class 11 | Part 11: Hemichordata

Phylum Hemichordata: General Characters

Hemichordata was earlier considered as a sub-phylum of Chordata. Like chordates, it has pharyngeal gill slits.

• Grades of Organization: Organ system.
• Symmetry: Bilateral.
• Germ Layers: Triploblastic.
• Coelom: Coelomate.
• Habit and Habitat: Exclusively marine.
• Digestive System: Complete.
• Respiratory System: Gills.
• Circulatory System: Open type.
• Reproduction:
• Dioecious.
• External fertilization.
• Development is indirect.


• Unique Features:
• Worm-like cylindrical body formed of anterior proboscis, a collar and a long trunk.
• Collar bears stomochord (a rudimentary structure similar to notochord).
• Excretion by Proboscis gland.
• Examples:
• Balanoglossus (Tongue worm)
• Saccoglossus

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1. Basis of Classification 2. Porifera 3. Cnidaria 4. Ctenophora 5. Platyhelminthes 6. Aschelminthes 7. Annelida 8. Arthropoda 9. Mollusca 10. Echinodermata 11. Hemichordata 12. Chordata - up to Sub phylum Vertebrata 13. Chordata - Cyclostomata, Pisces 14. Chordata - Tetrapoda

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