Ncert Exercises & Solutions

40. Give an example for each of the following

(a) A viviparous animal

(b) A fish possessing a poison sting

(d) An organ, which regulates buoyancy

(e) Animal, which exhibits alternation of generation

(f) Oviparous animal with mammary gland

(a) A viviparous animal is the one in which development of young ones is direct, later they provides nutrition to their offspring. It includes all mammals, except Platypus.

(b) A fish possessing a poison sting is Trygon (sting-ray). It is found on its tail. The poison released is strong enough to stun an animal.

(c) A fish possessing an electric organ Torpedo (electric ray). Electric Organ in Torpedo is locatedin its big round pectoral fin which is just behind the eye. Large Torpedo can generate a fish killing current of up to 200 volts.

(d) An organ, which regulates buoyancy is air bladder present in class—Osteichthyes. (e.g., Exocoetus, Catia).

(e) Animal exhibiting alteration of generation is Aurelia or jelly fish of phylum-—Cnidaria. It has two basic body forms called polyp and medusa are present. Polyp is sessile and cylindrical whereas medusa is umbrella shaped and free swimming form. Polyp produces medusa asexually and medusa forms polyps sexually (e.g., Obelia).

(f) Oviparous animal with mammary gland is Ornithorhynchus (duck-billed platypes). Duck bill platypus is the only mammal which lays egg and also bear mammary gland, which is a characteristic feature of mammals.

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