Numerous pouched gills 



Hy Old slit 



spiracle 



Parabranchial pumps. 

 Conus well developed 



-^ Cyclostomes 



-► Elasmo - 

 bronchs 



Modification of air bladder as 

 hydrostatic organ. Bui bus well 

 developed. Opercular pump. 



Air bladder persists as lung 



Teleosts 



Single 

 circulation 



Primitive 

 Bony fishes 

 e. g. Pol y pterus 



Lung supplied by 6th. aortic arch 



Return to left heart in 

 pulmonary vein. 

 Specialised A-V valve. 

 Ventricle divided. 



COELACANTHS some with 



ossified swimbladders 



Cutaneous respiration. Ventricle 



Di pnoi 



undivided. 



4 th. aortic arch 



systemic 



LEPID05AUR5 



Secondary septum 

 — ARCH0SAUR5 H separates 

 ventricles 



Right systemic 

 persists. 

 Homoiothermic. 

 Air sacs. 



Latimeria 



(single 

 circulation) 



Frogs 



Turtles 

 Lizards & 

 Snal<es 

 Crocodiles 



Birds 



->- Mammals 



Primary septum separates 



ventricles. 



Left systemic persists. 



Homoiothermic. Diaphragm. 

 changes during the evolution of the vertebrates 

 lave been mentioned in this book. 



Incomplete 



double 



circulation 



Complete 



double 



circulation 



