Which one of the following is a true fish as per the biological system

Which one of the following is a true fish as per the biological system of classification?

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Silverfish

Jellyfish

Cuttlefish

Flying fish

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-1 – 2018

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The question asks which option represents a ‘true fish’ according to biological classification. True fishes belong to the superclass Pisces (or equivalent phylogenetic groups like Osteichthyes and Chondrichthyes). Let’s examine the options:
A) Silverfish: This is an insect (Zygentoma order), not a fish.
B) Jellyfish: This is a marine invertebrate belonging to the phylum Cnidaria, not a fish.
C) Cuttlefish: This is a marine mollusc belonging to the class Cephalopoda, not a fish.
D) Flying fish: This is a type of marine ray-finned bony fish belonging to the family Exocoetidae. It is a true fish.

In everyday language, ‘fish’ is often used loosely, but in biology, a ‘true fish’ refers to aquatic vertebrates with gills that lack limbs with digits, typically belonging to the superclass Pisces.

Many animals with “fish” in their common name are not true fish (e.g., starfish, crayfish, shellfish). True fish include cartilaginous fish (sharks, rays) and bony fish (most common fish).

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