Hemichordata: Bilateral Symmetry — NEET Biology
✅ Asked in NEET 2023This phylum consists of a small group of worm-like marine animals with organ-system level of organisation. They are bilaterally symmetrical, triploblastic and coelomate animals. The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk. Circulatory system is of open type. Respiration takes place through gills. Excretory organ is proboscis gland. Sexes are separate. Fertilisation is external. Development is indirect.
NTA tests whether students can identify hemichordates as bilaterally symmetrical organisms with coelomate body structure. The common mistake is confusing hemichordates with echinoderms (also marine) and forgetting that hemichordates are triploblastic and bilaterally symmetrical, while adult echinoderms show radial symmetry. Remember: hemichordates have three body regions (proboscis, collar, trunk), open circulatory system, gill respiration, and external fertilization with indirect development. This concept appears in NEET 2023 and remains important because hemichordates are a unique link between invertebrates and chordates—testing bilateral symmetry helps distinguish them from other marine phyla.
Radial symmetry is not found in adults of phylum:- NEET Year: NEET 2023
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