How are bony fish better adapted to a swimming way of life than cartilaginpus fish?

Cartilaginous fishes have an internal skeleton made of cartilage and their skin is covered with placoid scales.

While, The bony skeleton of bony fishes is harder and heavier than cartilage. Bony fishes have either lungs or a swim bladder and hard, thin scales.

Does this help?

Cartilaginous fishes have an internal skeleton made of cartilage and their skin is covered with placoid scales.

The bony skeleton of bony fishes is harder and heavier than cartilage. Bony fishes have either lungs or a swim bladder and hard, thin scales.

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."

it would lead to upper respiratory infections and pneumonia.