In which of the following animals does blood go through the heart twice during each cycle?

Correct option is A

The correct answer is (a) Mammals, birds and reptiles.
Explanation:
· Blood goes through the heart twice in one cycle in animals with double circulation, which ensures efficient oxygenation.
· Mammals and birds: Have a four-chambered heart, with complete separation of oxygenated and deoxygenated blood.
· Reptiles: Most have a three-chambered heart, but partial separation occurs, enabling double circulation. However, crocodilians have a four-chambered heart, ensuring complete double circulation.
· Fishes: Have single circulation with a two-chambered heart, where blood passes through the heart only once per cycle.
Information Booster

• Double Circulation: Blood flows through the heart twice in one cycle—once for oxygenation in the lungs and once for distribution to the body.
  
• Advantages of Double Circulation: Higher efficiency, better oxygen supply, and separation of oxygenated and deoxygenated blood.
  
• Single Circulation: Blood flows through the heart only once per cycle, as seen in fishes.
  
• Crocodilians: The only reptiles with a four-chambered heart, allowing complete separation of blood streams.