Question map
Which one of the following has a bilateral symmetry in its body organization?
Explanation
Body symmetry in the animal kingdom is categorized into radial, bilateral, and asymmetrical types. Nereis, a marine polychaete worm belonging to the phylum Annelida, exhibits bilateral symmetry. This means its body is elongated along an anterior-posterior axis and can be divided into identical right and left halves through a single longitudinal plane [1]. In contrast, Asterias (sea star) and Echinus (sea urchin) are echinoderms that typically display radial or pentaradial symmetry as adults [1]. Sea anemones, belonging to the phylum Cnidaria, exhibit radial or biradial symmetry, where body parts are arranged around a central axis. While echinoderm larvae are bilaterally symmetrical, their adult forms, such as Asterias and Echinus, transition to radial symmetry. Therefore, among the given options, Nereis is the only organism characterized by a bilaterally symmetrical body organization in its adult stage.
Sources
- [1] https://deb.ugc.ac.in/Uploads/SelfLearning/HEI-P-U-0482/HEI-P-U-0482_SelfLearning_20230331142843.pdf