How do fishes cope up with two chambered heart where oxygenated and deoxygenated blood mix up unlike mammals which have four chambered heart for efficient flow of blood?

How do fishes cope up with two chambered heart where oxygenated and de

1.	How do fishes cope up with two chambered heart where oxygenated and deoxygenated blood mix up unlike mammals which have four chambered heart for efficient flow of blood?
Answer» How do fishes cope up with two chambered heart where oxygenated and deoxygenated blood mix up unlike mammals which have four chambered heart for efficient flow of blood?