Question

In which of the following vertebrate group/groups, heart does not pump oxygenated blood to different parts of the body?

• A. Pisces and Amphibians
• B. Amphibians and Reptiles
• C. Amphibians only
• D. Pisces only

Answer 1

The correct option is D Pisces only

Hint: In single circulatory system that 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. Oxygenated blood will not return to the heart.
• In double circulation as in mammals, heart pumps deoxygenated blood to the lungs for purification and oxygenated blood to the different parts of the body.

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 (Pisces) 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

• Fishes have a two-chambered heart which transports deoxygenated blood to gills but doesn't transport oxygenated blood to the different parts of the body.

Final step - Heart that does not pump oxygenated blood to different parts of the body is present in Pisces only.