Question

Assertion: Air bladder is absent in fishes.
Reason: Fishes generally respire through gills.
   (A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
   (B) Both Assertion and Reason are correct and Reason is not the correct explanation for the assertion.
   (C) Assertion is correct but Reason is incorrect.
   (D) Assertion is incorrect Reason is correct.

Answer 1

Hint: The air bladder is a structure that helps fishes to swim in the water. They have specialized structures that help them to take in dissolved oxygen in the water, and it plays an important role in respiration.

Complete step by step answer: The very first statement says that fishes lack air bladder which is incorrect as they have them. The ‘air bladder’ or ‘swim bladder’ or ‘fish maw’ is an internal organ in fishes (bony-fishes) which is filled by the gas that controls buoyancy and helps in swimming. The air bladder is evolutionarily homologous to the lungs. The gas/tissue interface at the swim bladder produces a strong reflection of sound, which is used in sonar equipment to find fish. The reason is correct, as gills are the respiratory organs of many aquatic organisms that extract dissolved oxygen from water and excretes carbon dioxide. Gills are tissues that are like short threads, protein structures called ‘filaments’. These filaments have many functions including the transfer of ions and water as well as the exchange of oxygen, carbon dioxide, acids and ammonia.

Additional Information: The use of air bladder is for humans too. In some Asian culture, the swim bladders of certain large fishes are considered a food delicacy. In China, they are known as fish maw and are served in soups or stews. The vanity price of a vanishing kind of maw is behind the imminent extinction of the Vaquita; the world’s smallest dolphin species. Fish gills are the preferred habitat of many ectoparasites (parasites attached to the gill but living out of it); the most common are monogeneans and certain groups of parasitic copepods, which can be extremely numerous.
Hence, the correct answer is option D.

Note: ‘Charles Darwin’ remarked about the homologous nature of air bladder to lungs in the book ‘On the Origin of Species.’ Darwin reasoned that the lung in air-breathing vertebrates had derived from a more primitive swim bladder.