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Pisces or Class Fish is the largest group of chordates which includes 25000 species of fishes. Study of fishes is called Ichthyology.
Fish is an aquatic gill breathing gnathostomates whose stramlined body is provided with paired fins and covered over dermal scales.
Super Class pisces is divided into two classes:
Chondrichthyes
Osteichthyes
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Chondrichthyes are Cartilagineous fishes. This class is also called Elasmobronchi. It has exclusively marine fishes with endoskeleton made of cartilage. Their skin has tiny shark enamel coated denticles called Placoid Scales. They are heterocercal and Mouth is present at ventral to tail fins. They have exposed 5 gills on each sides.
Example Shark, Ray fishes, Dog dish etc
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These fishes are Bony Fishes. This group is also called Teleostomi, They are found in both marine and fresh water. Their endoskeleton is made up of bones. Their skin has thin bony plates called cycloid or ctenoid. Their gills are covered with outer skin called operculum. Tain fin is homocercal and mouth is present at anterior tip.
Examples Sea Horse, Gold fish, Eel etc
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They have gill to breath
Streamlined body to move in fast moving water
All fishes are cold-blooded.
Fins are present for locomotion
They have great sense of smell
They have air bladder to be bouncy
Chondrichthyes are exclusively marine fishes while Osteichthyes are both fresh water and marine water living.The skeleton of Chondrichthyes is made of cartilage while the skeleton of Osteichthyes is made of bones.The gills of Chondrichthyes is NOT covered with operculum while the gills of Osteichthyes are covered with outer skin operculum. Â The skin of Chondrichthyes has tiny shark enamel coated denticles called Placoid Scales while the skin of Osteichthyes has thin bony plates called cycloid or ctenoid.The tail of Chondrichthyes is Heterocercal and mouth is ventral to the tail fins while the tail of Osteichthyes is homocercal and the mouth is present at anterior tip._____________________________________Best Regards,'Borz'
