Question

In a fish that has an air-breathing organ,

a. there are not likely to be functioning gills.
b. the blood leaving the ABO mixes with blood leaving the gills.
c. the blood leaving the ABO mixes with systemic venous blood.
d. the blood enters the ABO following its exit from the gills.
e. All of the above

Answer 1

The correct answer is the blood leaving the ABO mixes with systemic venous blood, as fish with ABOs still have a single circulatory loop with the ability to supplement oxygen intake when necessary.

Step-by-step explanation:

In a fish that has an air-breathing organ (ABO), the correct statement related to the circulatory system is the following: the blood leaving the ABO mixes with systemic venous blood. This statement reflects the fact that in fish with both gills and an air-breathing organ, the oxygenated blood from the ABO would typically mix with the venous blood carrying carbon dioxide and other waste products from the rest of the body before it is sent back to the heart to be pumped to the gills. Fish maintain a single circulatory loop, and while gills are the primary respiratory organ for gas exchange, some fish have additional structures for breathing air, typically to supplement oxygen intake when water oxygen levels are low.