Question

Assertion -In fishes, heart is Venous.
Reason-Only veins are present in the heart of fishes.
A) Both assertion and reason are correct and reason is the correct explanation of assertion.
B) Both assertion and reason are correct and reason is not the correct explanation of assertion
C) Assertion is correct but reason is incorrect.
D) Assertion is incorrect and the reason is correct.

Answer 1

Hint: A venous heart is two chambered. Venous hearts receive impure blood from veins and pump it directly to gills for oxygenation.

Complete answer:
To answer this question, we must know the type of heart present in fishes and also how it works.
In fishes, the type of blood circulation is single. It means that blood passes only once in one complete cycle. The respiratory organ of fishes is gills. The heart sends the deoxygenated blood for oxygenation to the gills. The heart of fishes is 2 chambered. It means only one atrium and one ventricle is present. The de-oxygenated from the body is carried by the sinus venosus veins to the atrium heart. It is then sent to gills for oxygenation by bulbus arteriosus. After oxygenation, the oxygenated blood is carried to different parts of the body by the help of arteries. So, in fishes, both vein and arteries are present in heart for blood circulation.

Thus, the correct answer is (C). Assertion is correct but the reason is incorrect.

Note:Fish have the simplest circulatory system where the blood circulation is completed in a single circuit. The fish heart has both entry and exit compartments called the chambers- one atrium to receive impure blood and one auricle to transport oxygenated blood to the body.