Which of the following animals belong to same class ?

Question

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Correct — option (4), 'Torpedo, Pristis, Hippocampus, Anabas'. Every name in the question is a genus, so the work is to place each one in its class and then find the option in which all four names sit together. Torpedo is the electric ray, Pristis the sawfish — both are cartilaginous fishes, with a skeleton of cartilage, a ventral mouth, placoid scales and no air bladder. Hippocampus is the sea horse and Anabas the climbing perch, both bony fishes with a bony endoskeleton, an operculum covering the gills and an air bladder. The two remaining names are not fishes at all: Ichthyophis is a limbless caecilian and belongs to class Amphibia, and Calotes is the garden lizard and belongs to class Reptilia. Test the options against that: option (1) puts the amphibian Ichthyophis among three fishes, option (2) puts both the amphibian and the reptile among two fishes, and option (3) puts the reptile Calotes and the amphibian Ichthyophis among two fishes. Only option (4) is free of any non-fish — all four of Torpedo, Pristis, Hippocampus and Anabas are fishes, which is the grouping the question is after, fishes being taken here as a single class (Pisces) as the older classification does. Note the finer point that the question does not turn on: under the scheme followed by NCERT, fishes are split into two classes, Chondrichthyes for Torpedo and Pristis and Osteichthyes for Hippocampus and Anabas. Even on that finer split option (4) is the only defensible choice, because it is the only set containing nothing but fishes while the other three each mix a tetrapod class into the list.

Why the other options are wrong — (a) Three of these four are fishes, but Ichthyophis breaks the set. It is a caecilian — a burrowing, limbless amphibian of the order Gymnophiona — and the name misleads exactly as intended, since 'Ichthyo-' means fish and the animal is snake-like in appearance. It is an amphibian on every diagnostic count: a moist glandular skin without scales of the fish type, and the amphibian pattern of respiration and development. This is the commonest wrong choice in this question, because a candidate who has correctly excluded the lizard Calotes may still take a name beginning with 'Ichthyo' for a fish.  (b) This option gathers three different classes into one list. Hippocampus, the sea horse, and Anabas, the climbing perch, are bony fishes; Ichthyophis is an amphibian; Calotes, the garden lizard, is a reptile with a dry scaly skin, internal fertilisation and shelled eggs. No two of those three classes can be merged under any scheme of classification, so the option fails at once. It is the sort of set that catches a candidate who is grouping by habitat or body form — small, elongated, tropical — rather than by the class characters that actually decide the question.  (c) Here the reptile Calotes and the amphibian Ichthyophis are both mixed with two fishes, Pristis the sawfish and Hippocampus the sea horse, so the option spans three classes and cannot be the answer. It is worth noticing that it also mixes a cartilaginous fish with a bony one, so it fails on the finer classification as well as on the coarse one. Any option containing Calotes can be dismissed before any thought is given to the fishes, because the garden lizard is the one unambiguously non-aquatic animal in the whole question.

Concept: This is a question about the classes of the vertebrates and about the genus names that a syllabus uses as their standard examples. The cartilaginous fishes, Chondrichthyes, have an entirely cartilaginous endoskeleton, a mouth placed on the underside of the head, gill slits without an operculum, tough placoid scales and no air bladder, so they must swim to stay afloat; Torpedo, the electric ray, which carries electric organs, and Pristis, the sawfish, with its toothed rostrum, are the standard examples. The bony fishes, Osteichthyes, have a bony skeleton, gills covered by an operculum, cycloid or ctenoid scales and an air bladder that controls buoyancy; Hippocampus, the sea horse, and Anabas, the climbing perch that can breathe air and move over land, are the examples usually printed. Amphibia, to which Ichthyophis belongs, are the first tetrapod class, tied to water for reproduction and with a moist skin used in respiration; the caecilians are the limbless order within it. Reptilia, to which Calotes belongs, are the first fully terrestrial class, with dry scaly skin, internal fertilisation and shelled amniotic eggs. The habit the question rewards is holding a small stock of genus names with their classes attached, rather than reasoning from the animal's shape.

State PCS 2024 Q61 — Science & Technology PYQ with Answer

State PCS 2024 Q61 — Science & Technology PYQ with Answer