Question

Assertion: Amphibians heart consists of two auricles and one ventricle.
Reason: The deoxygenated blood is returned to the heart through sinus venous.
A. Both Assertion and Reason are correct and Reason is the correct explanation for the Assertion
B. Both Assertion and Reason are correct and Reason is not the correct explanation for the Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect

Answer 1

Hint: In different vertebrate groups, the heart is internally divided into a varied number of interconnecting chambers. In all the vertebrates, the heart has one or two auricles and one or two ventricles. These chambers are called true chambers.

Complete answer: The amphibians were the first vertebrates to invade the land but they are not fully adapted to terrestrial life. They and their eggs have no protective coat to check the evaporative water loss. Therefore they are found in the damp places and they breed in water.
The amphibians have evolved from the lung-breathing, lobe-finned, bony fishes. The paired fins in the bony fishes had a fleshy lobe and they gave rise to limbs. This ancestral group is at present represented by a “living fossil” Latimeria, a lobe-finned fish of deep waters of Indian ocean.
The heart of amphibians receives both deoxygenated and oxygenated blood and is often called arteriovenous heart. It is three chambered i.e. with two auricles and a ventricle. Two accessory chambers that are sinus venosus and truncus arteriosus are also present. Thus the heart supplies mixed blood to the body parts. Renal portals system is well developed and red blood corpuscles in them are oval, biconvex and nucleated.
So, the correct answer is “Option A”.

Note: In all vertebrates including human beings, there is a single heart. It is a hollow muscular organ which is composed of cardiac muscle fibres. It is the pumping organ of the blood vascular system. It receives the blood from and pumps blood to the various organs and tissues of the body. It does so through, rhythmical, spontaneous contractions.