During a marine embryological survey, an organism is identified as having a bilaterally symmetrical, free-swimming larval stage, but it later metamorphoses into a sessile adult possessing a triploblastic enterocoelous coelom, a mesodermal endoskeleton of calcareous ossicles, and a water vascular system. Which of the following character combinations uniquely separates this adult organism's phylum from Phylum Mollusca and Phylum Annelida?
- Secondary radial symmetry with tube feet powered by a hydraulic canal systemAnswer
- BMetameric segmentation with excretory metanephridia and closed circulation
- CUnsegmented soft body enclosed by a mantle that secretes a hard shell and possesses a radula
- DChitinous exoskeleton with jointed appendages and Malpighian tubule excretion
Answer
Secondary radial symmetry with tube feet powered by a hydraulic canal system
The stem describes Phylum Echinodermata. Echinoderms display secondary radial (pentaradiate) symmetry as adults and utilize a unique water vascular system (ambulacral system) connected to tube feet for locomotion, food gathering, and respiration, distinguishing them from molluscs, annelids, and arthropods.
Step-by-Step Solution
Key Concept
Diagnostic features and metamorphosis of Phylum Echinodermata compared to other higher invertebrates