Annelida: Segmented Coelomate Body — NEET Biology
✅ Asked in NEET 2019They may be aquatic (marine and fresh water) or terrestrial; free-living, and sometimes parasitic. They exhibit organ-system level of body organisation and bilateral symmetry. They are triploblastic, metamerically segmented and coelomate animals. Their body surface is distinctly marked out into segments or metameres and, hence, the phylum name Annelida (Latin, annulus: little ring). They possess longitudinal and circular muscles which help in locomotion. Aquatic annelids like Nereis possess lateral appendages, parapodia, which help in swimming. A closed circulatory system is present. Nephridia (sing. nephridium) help in osmoregulation and excretion. Neural system consists of paired ganglia (sing. ganglion) connected by lateral nerves to a double ventral nerve cord. Nereis, an aquatic form, is dioecious, but earthworms and leeches are monoecious. Reproduction is sexual.
NTA tests whether students understand that annelids are triploblastic, bilaterally symmetric, coelomate animals with distinct body segmentation (metameres). The key concept is their closed circulatory system, paired ganglia with ventral nerve cord, and presence of nephridia for excretion/osmoregulation. Students often confuse annelids with arthropods (also segmented) and miss that annelids lack jointed appendages—only aquatic forms like Nereis have parapodia. Another common mistake is forgetting that some annelids (earthworms, leeches) are monoecious while Nereis is dioecious. Remember: segmented + closed circulation + nephridia = Annelida; the organ-system level organization distinguishes them from lower phyla.
This paragraph was tested 3 times in NEET.
Consider the following features: A) Organ‐system level of organization B) Bilateral symmetry C) True coelomates with segmentation of body Select the correct option of animal groups which possess all the above characteristics. NEET Year: NEET 2019
Which of the following animals are true coelomates with bilateral symmetry? NEET Year: NEET 2019
Which of the following animals does not undergo metamorphosis? NEET Year: NEET 2018
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