Question: From NCERT 100% NCERT covered from Particular Keyword. NEET 2015 Explanations are 100% from NCERT | [Difficult level: Easy]
Which of the following represent the correct combination without any exception?
Characteristic | Class |
(1) Mammary gland; hair on body; pinnae; two pairs of limbs | Mammalia |
(2) Mouth ventral; gills without operculum; skin with placoid scales; persistent notochord | Chondrichthyes |
(3) Sucking and circular mouth; jaws absent; integument without scales; paired appendages | Cyclostomata |
(4) Body coverd with feathers; skin moist and glandular; lungs with air sacs; fore limbs form wings | Aves |
Answer:
(2) Mouth ventral; gills without operculum; skin with placoid scales; persistent notochord | Chondrichthyes |
👉Class – Chondrichthyes
They are marine animals with streamlined body
and have cartilaginous endoskeleton
(Figure 4.19). 
Mouth is located ventrally.
Mouth is located ventrally.
Notochord is persistent throughout life. Gill
slits are separate and without operculum (gill
cover). The skin is tough, containing minute
placoid scales. Teeth are modified placoid
scales which are backwardly directed. Their
jaws are very powerful. These animals are
predaceous. Due to the absence of air bladder,
they have to swim constantly to avoid sinking.
Heart is two-chambered (one auricle and one ventricle).
Some of them have electric organs (e.g., Torpedo) and
some possess poison sting (e.g., Trygon). They are
cold-blooded (poikilothermous) animals, i.e., they lack
the capacity to regulate their body temperature. Sexes
are separate. In males pelvic fins bear claspers. They
have internal fertilisation and many of them are
viviparous.
Examples: Scoliodon (Dog fish), Pristis (Saw fish),
Carcharodon (Great white shark), Trygon (Sting ray).
