Question

Distinguish between cartilaginous fishes and bony fishes.

Answer 1

Hint: Gill-bearing aquatic craniate animals are the fishes that don't have limbs with digits. A fish that has a skeleton made up of cartilages are known as Cartilaginous fish and a fish whose skeleton is made up of bones is known as Bony fishes.

Complete answer
-There are two types of fishes Cartilaginous fishes and Bony fishes. It can be very easy to understand and differentiate them wherever necessary when we learn the differences between these two types of fishes.
-The most obvious difference between Bony and cartilaginous fishes depend upon the fact that the skeleton of Bony fish is generally made up of bones whereas the skeleton of Cartilaginous fish is generally made up of cartilage.
-More than 20,000 species of fishes are present in the world belonging to the class Chordata of the superclass Pisces.
-Based on this category it is classified as either Osteichthyes or Chondrichthyes (bony fish or cartilaginous fish).
The difference between them is -

BONY FISH	CARTILAGINOUS FISH
Also known as teleostomi and considered as the largest class in the phylum Chordata.	Also known as Elasmobranchii of this class of fishes.
Their endoskeleton is made up of bone and has a mouth opening at its anterior tip.	Their endoskeleton is generally made of cartilage
Based on whether the outer edges are spiny or smooth their exoskeleton is made up of thin Bony plates known as cycloids	Their exoskeleton consists of very tiny denticles surrounded by lots of sharp enamel known as placoids.
These fishes can be found in both the Marine and freshwater ecosystem	These fishes can only be found in the Marine ecosystem.
The tail fin of these fishes is homocercal	The position of the tail fins of these fishes is heterocercal
They have an operculum present on both sides of their gills.	These fishes have five gills that are overly exposed on both sides and the operculum is absent.
Eggs are externally fertilized by them	These fishes have an internal mode of fertilization.
Flying fish, Globefish, Sea horses, and Eels belongs to this category	Dogfish, Skates, Electric ray torpedo, and Sharks belong to this category.

Note:
-A fish that are characterized by the presence of bone tissues is known as Bony fish and they are also known as Osteichthyes. Most of the fishes belong to this taxonomic order and divided into two subgroups i.e Actinopterygii (ray-finned) and Sarcopterygii (lobe-finned).
-A fishes that are characterized by the presence of cartilage are known as cartilaginous fish and divided into two subgroups i.e. Elasmobranchii and Holocephali.