UPSC Prelims 2010 Q124: Science & Technology – Biology

UPSC Prelims 2010, General Studies Paper I · Science & Technology

From the point of view of evolution of living organisms, which one of the following is the correct sequence of evolution ?

Answer: (b) Shark - Tortoise - Otter

Explanation

The correct evolutionary sequence

These three animals represent different stages in vertebrate evolution, from early fish to later mammals.

Option	Verdict	Reason
(a) Otter - Tortoise - Shark	Incorrect	This sequence is reversed; mammals (otter) evolved after, not before, reptiles (tortoise) and fish (shark)
(b) Shark - Tortoise - Otter	Correct	Sharks (fish) are among the earliest vertebrates, followed by tortoises (reptiles), and later by otters (mammals) — matching the correct evolutionary timeline
(c) Tortoise - Shark - Otter	Incorrect	This misorders fish and reptiles; fish evolved before reptiles, not after
(d) Shark - Otter - Tortoise	Incorrect	This places mammals (otter) before reptiles (tortoise), which is historically backwards

Evolutionary sequence of vertebrate classes:

Answer: (b) Shark - Tortoise - Otter.

(a) Incorrect. This sequence is entirely reversed from the actual evolutionary order.
(b) CORRECT. Fish (Shark) → Reptiles (Tortoise) → Mammals (Otter) is the correct evolutionary sequence.
(c) Incorrect. This misorders fish and reptiles, placing reptiles before fish.
(d) Incorrect. This places mammals before reptiles, which is historically backwards.

The correct vertebrate evolutionary sequence is Fish (Shark) → Reptiles (Tortoise) → Mammals (Otter).

Correct evolutionary sequence: Shark (fish) → Tortoise (reptile) → Otter (mammal).

Reversing the entire evolutionary order, placing mammals first.
Swapping the order of fish and reptiles, two of the earliest vertebrate classes.
Not knowing the broad fish → amphibian/reptile → mammal evolutionary timeline.

Vertebrate evolution timeline: fish first, then reptiles, then mammals. Shark-Tortoise-Otter follows this exactly.