UPSC Prelims 2002 Q127: Science & Technology – Biology
Which one of the following statements is NOT correct?
- (a) All echinoderms are viviparous
- (b) Round worm has no circulatory system
- (c) In bony fishes, swim bladder is usually present
- (d) In cartilaginous fishes, fertilisation is internal
Answer: (a) All echinoderms are viviparous
Explanation
Animal biology: the statement that is NOT correct
| Statement | Verdict |
|---|---|
| All echinoderms are viviparous | Not correct — most echinoderms (starfish, sea urchins) are oviparous with external fertilisation |
| Round worm has no circulatory system | Correct — the pseudocoelom carries fluids |
| Bony fishes usually have a swim bladder | Correct — it controls buoyancy |
| Cartilaginous fishes show internal fertilisation | Correct — males have claspers |
The question asks for the statement that is NOT correct. Echinoderms such as starfish and sea urchins shed eggs and sperm into the water, so they are oviparous and not viviparous. The other three statements are correct. The bank had dropped the word NOT, and the stored key (a) fits only that reading.
Answer: (a) All echinoderms are viviparous.
Why each option is right or wrong
- (a) CORRECT. This is the false statement; echinoderms are mostly oviparous.
- (b) Incorrect. This statement is true, since round worms lack a circulatory system.
- (c) Incorrect. This statement is true, since most bony fishes have a swim bladder.
- (d) Incorrect. This statement is true, since cartilaginous fishes fertilise internally.
Key point
Echinoderms: starfish, sea urchin, sea cucumber; mostly dioecious with external fertilisation and larval stages.
Remember
Echinoderms are mostly oviparous; sharks fertilise internally.
Common mistakes
- Reading the stem as 'correct' and choosing (c), a true statement.
- Thinking echinoderms give birth to young ones.
- Forgetting claspers in cartilaginous fishes.
Exam tip
'All' statements about a large group are often the false ones.
Sources
- NCERT Class XI Biology — Animal Kingdom
- Encyclopaedia Britannica — echinoderm