Which of the following represents the correct combination without any exception? (Characteristics – Class)
- Sucking and circular mouth; jaws absent, integument without scales; paired appendages. – Cyclostomata
- Body covered with feathers; skin moist and glandular, forelimbs form wings; lungs with air sacs. – Aves
- Mammary gland; hair on body; pinnae; two pairs of limbs. – Mammalia
- Mouth ventral; gills without operculum; skin with placoid scales; persistent notochord. – Chondrichthyes
Answer
(4) Mouth ventral; gills without operculum; skin with placoid scales; persistent notochord. – Chondrichthyes
Solution
As per NCERT, Chondrichthyes are marine cartilaginous fishes: the mouth is located ventrally, the notochord is persistent throughout life, gill slits are separate and without operculum (gill cover), and the skin is tough, containing minute placoid scales.
∴ Option (4) is correct without any exception.
⇒ (1) Cyclostomes have a sucking and circular mouth without jaws and scales, but paired fins (appendages) are absent.
⇒ (2) In Aves, the skin is dry without glands except the oil gland at the base of the tail.
⇒ (3) Some mammals lack pinnae (e.g. whales) and in some limbs are modified (e.g. flippers), so it has exceptions.
Answer: (4)