Question

Endoskeleton is cartilaginous in
A. Elasmobranchii
B. Dipnoi
C. Mollusca
D. Osteichthyes

Answer 1

Hint:-We know that every organism has some bones in it to make the organism mechanically stable. The combination of all the bones present in an organism is called a skeleton. However, the skeleton in an organism can lie externally or internally. The skeleton which lies inside of the organism’s body is called an endoskeleton. The endoskeleton is mainly made up of two major tissues which are bone and cartilage. However, in some of the cases, the organism may consist of one of these two tissues.

Complete answer:
A. One of the classes which include the cartilaginous fishes is Elasmobranchii. The fishes of this group contain gill pouches that are normally homologous to the lungs of the amphibians like frogs.
B. The lungfishes are the organisms that are included in the subgroup of Dipnoi. Generally, the fishes of this group contain an endoskeleton which is made up of bones.
C. As we already know, the second-largest phylum of the animal kingdom includes the class of Mollusca. This group typically includes predominantly marine species. They have an exoskeleton.
D. The Bony fishes are the organisms that are included in the subgroup of Osteichthyes. However, organisms like bony fishes and the others which are included in this group normally contain the endoskeleton which is made up of bones.
Thus, we can say that the endoskeleton which is made up of cartilaginous is present in the group of Elasmobranchii.
So, the correct answer is Elasmobranchii.

Note:- As we know already, one of the subclasses of the phylum Chondrichthyes, or cartilaginous fish is Elasmobranchii. The class of Elasmobranchii typically include the sharks and the rays, skates, and sawfish. They have four to seven pairs of gill clefts opening individually to the exterior. They also contain rigid dorsal fins and small placoid scales on the skin.