Fishes have an only two-chambered heart with an atrium and a ventricle, and the chambers of the heart which receive the blood from body tissues are called auricles.
Fishes respire through their gills.
The human heart has four chambers.
Two relatively small upper chambers called atria and two larger lower chambers called ventricles.
Amphibians; and the reptiles (except crocodiles); have a 3-chambered heart with two atria and a single ventricle.
Frogs respire through their skin.
The lizard has a three-chambered heart. Shark has a two-chambered heart.