Question

Single circulation blood flows through the heart only once during one cycle of passage through the body. This is exhibited by

• A. Labeo, Chameleon, Salamander
• B. Hippocampus, Exocoetus, Anabas
• C. Hyla, Rana, Draco
• D. Whale, Dolphin, Turtle

Answer 1

The correct option is B Hippocampus, Exocoetus, Anabas

Hint: Single circulatory system is present in organisms with 2-chambered heart (one auricle and one ventricle).

Part 1 - Definition - Single circulation system

• The type of circulatory system in which the blood passes only once through the heart in each complete circuit of the body.
  
• First, the blood will pass through the heart to gills, then after purification, blood will be distributed to different parts of the body.
  
• In double circulation as in mammals, four chambers that completely separate the oxygenated and deoxygenated blood; it pumps only oxygenated blood through the body and deoxygenated blood to the lungs.

Part 2 - Two chambered heart

• As the name suggests in a two-chambered heart, there are only two chambers: Atria (Auricle) and Ventricle.

Atria (receiving chambers) - are the first stops for blood entering the heart.
Ventricle (pumping chambers) - are the chambers that push blood out of the heart.

• Animals with 2-chambered heart use gills for gaseous exchange (respiration).

Part 3 - Examples of organisms

• Fishes have the simplest circulatory systems of the vertebrates: blood flows in one direction from the two-chambered heart to the gills and then the rest of the body.
• Amphibians and reptiles have 3-chambered heart while birds and mammals have 4-chambered heart.

Part 4 - Conclusion

• From the above discussion, we can conclude single circulation is present in organisms with a 2-chambered heart which in turn is seen in fishes.
• Labeo, hippocampus, exocoetus, and anabas belongs to class Pisces (fishes).
• Chameleon, turtle, and draco (flying lizard) belongs to class Reptilia.
• Hyla, rana, and salamander belong to class Amphibia while dolphin and whale belongs to class Mammalia.

Final step - Single circulation blood flows through the heart only once during one cycle of passage through the body. This is exhibited by Hippocampus, exocoetus, anabas.