Crocodile and penguin are similar to whale and dogfish in which one of the following features?
- Possess a solid single stranded central nervous system
- Lay eggs and guard them till they hatch
- Possess bony skeleton
- Have gill slits at some stage
Answer
(4) Have gill slits at some stage
Solution
Crocodile (Reptilia), penguin (Aves), whale (Mammalia) and dogfish (Chondrichthyes) are all chordates.
As per NCERT, the three fundamental features of chordates are notochord, a dorsal hollow tubular nerve cord and paired pharyngeal gill slits.
⇒ All of them have pharyngeal gill slits at least at some stage (embryonic stage).
∵ Chordates have a hollow (not solid) nerve cord, whale is viviparous and dogfish has a cartilaginous skeleton,
∴ the common feature is gill slits at some stage.
Answer: (4)