Animal Kingdom - Notes | Class 11 | Part 8: Arthropoda

Phylum Arthropoda (Joint-Legged Animals): General Characters

Arthropoda is the largest phylum. Over two-thirds of all named species are arthropods.

• Grades of Organization: Organ system.
• Symmetry: Bilateral symmetry.
• Germ Layers: Triploblastic.
• Coelom: Coelomate.
• Habit and Habitat: Cosmopolitan.
• Digestive System: Complete.
• Respiratory System: Gills/book gills/trachea/book lungs.
• Circulatory System: Open type.
• Reproduction:
• Mostly dioecious.
• Usually internal fertilization.
• Mostly oviparous.
• Development is direct or indirect.


• Unique Features:
• Jointed appendages.
• Body has 3 regions: head, thorax & abdomen.
• Body is covered by chitinous cuticle (exoskeleton).
• Excretion by Malpighian tubules.
• Sensory organs are antennae, compound & simple eyes, statocysts (balance organs).
• Examples:
• Spider, Scorpion, Crab, Prawn, Insects etc.
• Economically important insects: Apis, Bombyx, Laccifer.
• Vectors: Mosquitoes (Anopheles, Culex & Aedes), Housefly etc.
• Gregarious pest: Locusta.
• Living fossil: Limulus (King crab).

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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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