Which one of the following statements is not correct?
The statement "All echinoderms are viviparous" is not correct. Most echinoderms are oviparous, reproducing through external fertilization where eggs are laid and develop outside the mother's body. Viviparity, where offspring develop inside the mother and are born live, is a rare occurrence in a few specialized echinoderm species, not a general characteristic of the entire phylum.
Option (B): Roundworms (Phylum Nematoda) lack a specialized circulatory system. The transport of nutrients and gases within their body occurs primarily through diffusion, facilitated by the pseudocoelom fluid.
Option (C): In bony fishes (Class Osteichthyes), a swim bladder is commonly present. This gas-filled organ plays a crucial role in maintaining buoyancy, allowing the fish to control its depth in water without expending excessive energy.
Option (D): Cartilaginous fishes (Class Chondrichthyes), which include sharks, rays, and chimaeras, exhibit internal fertilization. Males possess modified pelvic fins called claspers, which are used to transfer sperm into the female's reproductive tract.