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Chordate and non-chordate classes
Concepts tested here
- Osteichthyes
All Questions
2012 AIPMT-MAINS 1 question
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Which one of the following categories of animals is correctly described with no single exception in it?Bony fishes (class Osteichthyes) have four pairs of gills that are covered by an operculum on each side; this holds for the class without exception.
Mammals: not all are viviparous, since the monotremes (e.g., platypus, $Ornithorhynchus$) are oviparous.
Reptiles: crocodiles have a four-chambered heart, so 'three chambered heart' has an exception.
Sponges: most are marine but some, such as $Spongilla$, live in fresh water.
Hence the category described with no exception is the bony fishes.