Question

What are the three disadvantages of having a Skelton made of cartilage only? for example, in cartilaginous fishes.

Answer 1

The disadvantages of having a skelelton made of cartikage in fishes are:-

a)In cartilaginous fish , the gills are exposed and not protected by an external skin and that may cause harm to the fish whereas in bony fish ,gills are covered by external flap called operculum.

b)Cartilaginous fishes lack bone marrow for haemopoiesis .Instead, they produce RBC in the spleen and thymys organ whereas in bony fishes RBCs are produced in bone marrow by the process of haemopoiseis.

c) Cartlaginous fishes have only one set of jaw called oral jaw but bony fishes have two sets of jaw called oral jaw and pharyngeal jaw.Teeth are present along one dise of the jaw and the pharyngeal jaw   helps in digestion of food by processing in mouth before it enters the stomach.

d)Cartilaginous are not able to maintain internal buoyancy with the help of bladder because they didnot have that.They swim to the surface of water to take in air that helps to maintain their position in water .

e) Cartilage is not effective in protecting the fish .and are not very much effective in trasnmitting the muscle force.