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UPSC Prelims 2002 · Environment · Species Watch
Which one of the following statements is not correct?
- (a) All echinoderms are viviparous
- (b) Roundworm has no circulatory system
- (c) In bony fishes, swim bladder is usually present
- (d) In cartilaginous fishes, fertilization is internal
Show the answer and explanation
Answer: (a) All echinoderms are viviparous
This is the incorrect statement: most echinoderms (starfish, sea urchins) release eggs and sperm into water — they are not viviparous.
The idea
Echinoderms are the spiny-skinned sea animals: starfish, sea urchins, sea cucumbers. Almost all of them shed eggs and sperm into the sea, where fertilisation takes place. They do not give birth to live young.
Cartilaginous fish (sharks, rays): skeleton of cartilage, no swim bladder, fertilisation inside the body → Bony fish (rohu, sardine): skeleton of bone, swim bladder to float, eggs fertilised in water
Why the others are wrong
(b) True — roundworms have no circulatory system.
(c) True — bony fish use a swim bladder to control buoyancy.
(d) True — sharks and rays (cartilaginous fish) fertilise internally.
The trap
“All” in (a) is the giveaway.
Elimination technique
The question asks for the statement that is not correct, and option (a) begins with “All”. Absolute words usually mark the false statement in Environment PYQs.
Also know
A shark has no swim bladder; many swim to stay buoyant, while others rest on the bottom.
🔒 Echinoderms: external fertilisation, larvae. Sharks: internal fertilisation, no swim bladder.