"Starfish cannot be placed under4 the phylum pisces". Explain.
Organisms that belong to Class Pisces are fishes. They respire through their gills. They are cold-blooded or poikilothermic animals. Their skin is rough and covered with scales/plates which form the exoskeleton. They do not have limbs for locomotion, but they have paired or unpaired fins with the help of which they move in water.
Starfish is characterised by radial symmetry, several arms radiating from a central body. Mouth and anus are close together on the underside. Body is represented by a central disc covered by ossicles with spines called pedicellaria. Digestive system is complete. Tube feet are present for locomotion and respiration. They show very high power of regeneration.
Since the characteristics of starfish are entirely different from the characteristics of class Pisces, starfish cannot be placed under class Pisces. Instead, it possesses characteristics of phylum Echinodermata and hence, is placed under phylum Echinodermata.
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