CAPF AC 2021 Q25: Science & Technology – Biology
Which one of the following organisms does not possess notochord at any stage of its life cycle?
- (a) Holothuria
- (b) Herdmania
- (c) Exocoetus
- (d) Salamander
Answer: (a) Holothuria
Explanation
Which animal never has a notochord
How to think: a notochord is the mark of Phylum Chordata.
Every chordate has it at some stage of life.
So look for the animal that is not a chordate.
| Animal | Common name | Group | Notochord |
|---|---|---|---|
| Holothuria | Sea cucumber | Echinodermata (non-chordate) | Never |
| Herdmania | Sea squirt | Urochordata (protochordate) | Only in the larval tail |
| Exocoetus | Flying fish | Vertebrata, bony fish | In the embryo, replaced by backbone |
| Salamander | Salamander | Vertebrata, amphibian | In the embryo, replaced by backbone |
Answer: (a) Holothuria.
Why each option is right or wrong
- (a) CORRECT. Holothuria (sea cucumber) is an echinoderm, a non-chordate, so it never has a notochord.
- (b) Incorrect. Herdmania is a urochordate; its larva has a notochord in the tail.
- (c) Incorrect. Exocoetus (flying fish) is a vertebrate with a notochord in the embryo.
- (d) Incorrect. The salamander is an amphibian with a notochord in the embryo.
Key point
Notochord = chordates only. Echinoderms (starfish, sea urchin, sea cucumber Holothuria) are non-chordates. Herdmania is a urochordate with a notochord only in the larval tail.
Remember
Holothuria = sea cucumber = echinoderm = no notochord.
Common mistakes
- Marking Herdmania because the adult sea squirt has no notochord.
- Not knowing that Exocoetus is the flying fish, a true vertebrate.
- Treating all sea animals such as the sea cucumber as chordates.
Exam tip
Educated guess: a fish and an amphibian are clearly vertebrates, so (c) and (d) go. Between the two sea animals, the sea cucumber belongs with starfish, which have no backbone plan at all.
Sources
- NCERT Class XI Biology — Animal Kingdom (Echinodermata and Chordata)
- NCERT Class IX Science — Diversity in Living Organisms