- A Both share an open circulatory system and jointed legs adapted for benthic crawling as generally observed
- B Both have an endoskeleton of calcareous ossicles and a water vascular system with tube feet
- C Both reproduce mainly by asexual budding without any sexual phase in typical laboratory settings
- D Both lack any skeletal structure and rely on a soft protective mantle under usual circumstances
Correct answer: B. Both have an endoskeleton of calcareous ossicles and a water vascular system with tube feet
Explanation: Despite differing external shapes, all echinoderms, including Holothuria (sea cucumber) and Echinus (sea urchin), share a calcareous endoskeleton made of ossicles and a unique water vascular system with tube feet used in locomotion and feeding.
Concept context
Phylum-level classification of the animal kingdom from Porifera to Chordata, based on body symmetry, coelom, and segmentation. One of the most example-heavy chapters for NEET.