Clas pisces ………….. the fish

What is the characteristics of Pisces…..the fish ? have stream lined bodies with scaly skin . Have 4 fins for swimming. They live in water except mudskupper and lung fish. Their breathing organ is gill. Their heart is two chambered. Have external fertilisation. Are piokilothermic animals. Haven’t constant temperature. Use their lateral linesystem which is used for hearing. Fish can grouped into 2 those are ….. bony fish and cartilagenous fish