Answer: Cartilaginous endoskeleton, ventrally placed mouth, gill slits without operculum.
- A Bony endoskeleton, gills covered by operculum, terminal mouth according to most researchers
- B Cartilaginous endoskeleton, ventrally placed mouth, gill slits without operculum
- C Cartilaginous endoskeleton, four-chambered heart, feathers in the majority of cases studied
- D Bony endoskeleton, placoid scales, dorsal mouth as widely reported in standard practice
Correct answer: B. Cartilaginous endoskeleton, ventrally placed mouth, gill slits without operculum
Explanation: Chondrichthyes (e.g., Scoliodon, sharks) have a cartilaginous endoskeleton, ventrally placed mouth, and separate gill slits without an operculum, plus placoid scales. Osteichthyes have a bony skeleton and an operculum covering the gills.
Moving across the animal phyla, body organisation becomes progressively more complex: from no symmetry and cellular organisation (Porifera) through radial/diploblastic (Cnidaria), bilateral/acoelomate (Platyhelminthes), pseudocoelomate (Nematoda), to a true coelom with full organ systems (Annelida and beyond).
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.