SSC CGL 2024 Tier-I · 11 September 2024, Shift 2 · General Awareness · Question 5 of 100

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 6 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

How many chambers are there in the heart of fishes?

(a)4
(b)2
(c)3
(d)1

Answer

Why

Correct — B. A fish heart has two chambers — one atrium and one ventricle.

Blood runs a single circuit: the ventricle pushes deoxygenated blood to the gills, it picks up oxygen there, and it goes straight on to the body before returning to the atrium.

It passes through the heart once per complete circuit, so there is no second pump to build and no third or fourth chamber to separate — option (b).

Why the others are wrong

(a)
4 — Four chambers belong to birds, mammals and crocodiles, where oxygenated and deoxygenated blood are kept completely apart for double circulation.
(c)
3 — Three chambers — two atria and one ventricle — is the amphibian and general reptilian pattern, in which the two blood streams mix in the single ventricle.
(d)
1 — A one-chambered pump is not a vertebrate design. Even the fish heart separates a receiving chamber, the atrium, from a pumping chamber, the ventricle.

Concept

Vertebrate hearts are counted by chambers, and the count tracks how far oxygenated and deoxygenated blood are kept apart.

Fishes: two chambers with single circulation. Amphibians and most reptiles: three, two atria feeding one ventricle, so the streams mix. Crocodiles, birds and mammals: four, with complete separation and true double circulation.

In single circulation blood crosses the heart once per circuit. In double circulation it crosses twice, once on the pulmonary loop and once on the systemic loop.

The fish heart also has a sinus venosus before the atrium and a conus or bulbus arteriosus after the ventricle, but textbooks do not count these as chambers.

Key facts

A fish heart has two chambers, one atrium and one ventricle.
Fishes have single circulation, the heart pumping deoxygenated blood to the gills.
Amphibians and most reptiles have three-chambered hearts.
Crocodiles, birds and mammals have four-chambered hearts.

Study next

Single versus double circulationChamber counts across the vertebrate classesStructure of the human heart and its valves

Common traps

Counting the sinus venosus and conus arteriosus as chambers and answering three or four.
Grouping crocodiles with the other reptiles, when their heart is four-chambered.

Chamber counts, respiratory organs and class characteristics come off the same page of the syllabus — 10 Sep 2024, 16:00, GA Q.10 asks which listed characteristic is NOT one of the Aves.

Learn the vertebrate classes as a table rather than as isolated facts.

Related PYQs

No directly related past PYQ was found.