list the characteristics features that distinguish cartilaginous fishes with living jawless fishes
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Answer:
The main similarity between Jawless fish and cartilaginous skeleton is their skeleton makeup. Cartilaginous fish have an endoskeleton made primarily out of cartilage rather than bone. Cartilage is more flexible and softer than bone, especially due to lack of calcium that makes bones rigid. This is a similar feature to Jawless fish, which also have cartilaginous skeleton.
They however have some very distinctive differences. Some of their unique characteristics are;
Cartilaginous fish have ovoviviparous reproduction, which essentially means that they have internal fertilization. This is a characteristic that is contrast to jawless fish, which instead experience external fertilization.
Again the cartilaginous fish have jaws and paired fins, whereas jawless fish as the name describes, do not have jaws, plus they also have no paired fins.
The jawless fish include the lampreys and the hagfish. Jaws, fins, and stomachs are absent in the jawless fish. Features of the jawless fish include a notochord, paired gill pouches, a pineal eye, and a two-chambered heart.
The vast majority of cartilaginous fish survive in marine, or saltwater, habitats. These fish can be found throughout the world’s seas and oceans.
the characteristics features of cartilaginous fishes
(i) They are frequently marine called poikilothermic animals (i.e, they have the ability to adapt their body temperature).
(ii) The body is sideways packed and spindle-shaped
(iii) Notochord is persistent during a lifetime.
(iv) Mouth is ventral in place, the skin is dense containing minute placoid scales and teeth are transformed placoid scales. They have a powerful jaw and are predaceous by nature.
(v) Gill slits are usually five pairs and gill covering (operculum) are missing.
(vi) Heart is two-chambered with one auricle and one ventricle.