HSEB zoology notes | General characteristic of Pisces

The general characteristics of Pisces are as follows :

1.  Habitat : They are completely aquatic found in marine or freshwater. They are cold blooded (poikilothermic) animals.

2.  Body form : They have streamlined body or boat shaped and laterally compressed. Body is covered by cycloid or placetoid scales.

3.  Locomotion : Locomotion in Pisces is performed by paired fins (pelvic, pectorial fins) and unpaired fins (anal , dorsal , caudal fins).

4. Respiration : They respire through gills. Gills may or may not be covered by operculum.

5. Swim bladder may or may not be present and they two chambered heart.

6. Reproduction system : Sexes are separate in them (diocoius) and some show sexual dimorphism like cartilaginous fish and some don't like bony fish. Those who show sexual dimorphism have clasper for transferring sperm to female genital tract.

7. Development is direct and fertilization in Pisces is both internal and external.

HSEB zoology notes | Difference between cartilaginous fish and bony fish

The difference between Chondrichthyes (cartilaginous fish) and Osteichthyes (bony fish) are as follows: 

Chondrichthyes (cartilaginous fish)	Osteichthyes   (bony fish)
1.       They are marine.	They are both marine and fresh water.
2.       Swim bladder is absent.	Swim bladder is present.
3.     Endoskeletion is cartilaginous.
4.   Endoskeletion is bony.	No operculum. Spiracles are present.
5.  Gills are enclosed by operculum.	Mouth is at the presnt at the ventral region.
6.  Mouth is present at the terminal region of the     body.	Fertilization is internal.
7. Sexual dimorphism is distinct. They have clasper for transferring sperm to female genital tract. eg : Scoliodon , Torpedo (electric fish) etc	Sexual dimorphism is not distinct. Clasper are absent. eg : Labeo (rohu) ,  Exocoetus (flying fish) etc