The coelom (body cavity) is one of the most important features in animal classification because it reflects structural complexity and evolutionary advancement.

Why Coelom Is Useful

• Groups animals – Based on coelom, animals are divided into:
  
  • Acoelomates (no coelom, e.g., Platyhelminthes)
  • Pseudocoelomates (false cavity, e.g., Aschelminthes)
  • Coelomates (true coelom, e.g., Annelids, Molluscs, Arthropods, Chordates)
• Shows evolutionary level – Presence of coelom marks the transition from simple to complex body organization.
• Helps in organ development – A coelom allows better organ placement and function, especially circulatory and digestive systems.
• Basis of higher classification – Major animal groups (phylum level) are defined using coelom type.