Question

what is the meaning of notochord is "persistent" throughout life of class chondrichthyes

Answer 1

notochord is the primitive stage of the vertebral column which remains forever ie does not get changed or metamorphosed in the cases of cartilaginous fishea or chondricthes. in osticthes however there is a backbone and no notochord

Answer 2

The meaning of notochord is as follows:

Notochord is the main structural support of the body in vertebrates.

Notochord is persistent in Chondrichthyes throughout their life because they are chordates.

• Notochord becomes a part of the vertebral column, it is replaced with the cartilaginous vertebral column.

• For example Sharks, Fishes, Rays, etc are have the notochord.

• These fishes, Sharks belong to the class of Chondrichthyes. Notochord does not change in cartilaginous fishes or Chondrichthyes.

• Osteichthyes have a backbone so they don't have a notochord.