Coelom Types & Body Cavity Classification — NEET Biology
✅ Asked in NEET 2024Presence or absence of a cavity between the body wall and the gut wall is very important in classification. The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods, echinoderms, hemichordates and chordates. In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Such a body cavity is called pseudocoelom and the animals possessing them are called pseudocoelomates, e.g., aschelminthes. The animals in which the body cavity is absent are called acoelomates, e.g., platyhelminthes.
NTA tests whether you can distinguish between coelomates (body cavity lined by mesoderm), pseudocoelomates (scattered mesoderm pouches), and acoelomates (no cavity). Students often confuse pseudocoelom with true coelom and mix up which phyla belong to which category. The key trap: remembering that the presence and type of mesoderm lining defines the classification, not just the existence of a cavity. To ace this: coelomates = annelids, molluscs, arthropods, echinoderms, chordates; pseudocoelomates = aschelminthes; acoelomates = platyhelminthes. This concept is fundamental to animal classification and appears regularly in NEET.
Consider the following statements: A. Annelids are true coelomates; B. Poriferans are pseudocoelomates; C. Aschelminthes are acoelomates; D. Platyhelminthes are pseudocoelomates. Choose the correct answer. NEET Year: NEET 2024
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