JAMB - Biology (1994 - No. 7)
Which of the following combinations differentiates a bony fish from a cartilaginous fish? I. Presence of gills II. Absence of gill slits III. Possession of bony skeleton IV. Possession of laterally compressed body V. Possession of dorso-ventrally compressed body
I, II and III
I, III and IV
II, III and IV
II, III and V
Explanation
| CARTILAGINOUS FISHES | BONY FISHES |
| 1) Their endoskeleton is primarily made of cartilage. | 1) Their endoskeleton is entirely made of bone. |
| 2) Their exoskeleton is made of placoids. | 2) Their exoskeleton is made up of cycloids or thin bony plates. |
| 3) The position of their tail is heterocercal. | 3) Their tail fin is homocercal. |
| 4) possession of dorso-ventrally flattened body |
4) Possession of laterally compressed body |
| 5) They have 5 overly exposed gills (no operculum). | 5) They have an operculum on either side of their gills. |
| 6) In them the fertilization is through internal mechanisms. | 6) They fertilize their eggs externally. |
| Eg- dogfish, electric ray torpedo, and sharks. |
Eg- fying fish, globe fish, and sea horses. |
therefore, option c is correct.
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