biology notes class

THE EVOLUTION OF THE HEART • Heartis a muscular organ . As per evolutionary point of view the chamber of heart are, 1.SINGLE CHAMBER HEART • It is found in primitive chordates like amphioxus. • It is not a true heart. 2. TWO CHAMBER HEART • It is found in pises. • It is true heart chamber. • 2heart chamber                  a. Atrium- receving chmber                  b. Ventricle-pumping chamber • 2 chanber animals also contains gills for respiration. • Heart of fish receive only deoxygenated blood. • This type heart is calledbranchialheart or venus heart. • It is a single circulation path or haert. Sinus                                 atrium                    ventricle venosus                                                                                                                                                                              conus arteriosus  deoxyganated blood                            oxygenated