92. Choose the correct option based on your understanding of the circulatory system
P. Open circulatory system                         i. Fish
Q. Closed circulatory system                      ii. Frog
R. Three chambered heart                          iii. Earthworm
S. Two chambered heart                              iv. Grasshopper
(A) P-iv; Q-iii; R-ii; S-i
(B) P-iv; Q-i; R-ii; S-iii
(C) P-i; Q-iv; R-ii; S-iii
(D) P-i; Q-iii; R-iv; S-ii

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Understanding Circulatory Systems in Animals: Fish, Frog, Earthworm, and Grasshopper

The circulatory system transports oxygen, nutrients, and waste in animals. It comes in open and closed types, with heart chamber variations linked to evolutionary adaptations. This article breaks down a key biology MCQ on matching these features, perfect for students prepping for exams like NEET or class 12 biology.

Correct Answer: (A) P-iv; Q-iii; R-ii; S-i

This matching reflects standard zoology classifications: grasshoppers have open systems, earthworms closed, frogs three-chambered hearts, and fish two-chambered.

Detailed Explanation of Each Option

P. Open circulatory system → iv. Grasshopper
In an open circulatory system, blood (hemolymph) flows freely into body cavities (hemocoel) rather than staying in vessels. Grasshoppers (arthropods) exemplify this—heart pumps hemolymph into sinuses, bathing organs directly. Efficient for low-pressure needs in insects.

Q. Closed circulatory system → iii. Earthworm
A closed circulatory system keeps blood in vessels, enabling precise control and higher pressure. Earthworms (annelids) have this setup with a dorsal vessel acting as a heart, pumping blood through ventral vessels. Ideal for burrowing lifestyles needing efficient oxygen delivery.

R. Three chambered heart → ii. Frog
Frogs (amphibians) possess a three-chambered heart: two atria and one ventricle. This partially separates oxygenated and deoxygenated blood, better than fish but less than mammals. Suits their semi-aquatic life with pulmonary and systemic circuits.

S. Two chambered heart → i. Fish
Fish have a two-chambered heart (one atrium, one ventricle) suited to gill-based respiration. Blood flows from sinus venosus → atrium → ventricle → conus arteriosus → gills → body. Simple design matches single-circuit aquatic oxygen needs.

Why Other Options Are Incorrect

• Option (B) swaps Q (earthworm closed) with i (fish, which is closed but two-chambered, not the match) and S with iii—ignores earthworm’s definitive closed system.

• Option (C) wrongly assigns P to fish (fish have closed systems) and Q to grasshopper (open).

• Option (D) misplaces R (frog three-chambered) to iv and S to ii—frogs aren’t two-chambered.

Quick Comparison Table: Circulatory Systems