Answer 1

Characteristics of Osteichthyes:
(i) Marine and fresh-water fish with partial or full bony endoskeleton.
(ii) They have a spindle-shaped body and the skin is either naked or covered with cycloid or ctenoid scales.
(iii) Four pairs of gills are present for respiration. The gills are covered by operculum and are filamentous.
(iv) Cloaca is absent and anal and urogenital apertures are distinct. They excrete ammonia (ammonotelic animals).
Examples: Labeo and Protopterus.