Question

Which of the following characteristic features always holds true for corresponding groups of animals?

1	Cartilaginous endoskeleton	Chondrocytes
2	Viviparous	Mammalia
3	Possess a mouth with an upper and lower jaw	Chordata
4	3- chambered heart with incompletely divided ventricle	Reptilia

A. 1
B. 2
C. 3
D. 4

Answer 1

Hint: Animals that belong to chordates are fundamentally characterised by the presence of a notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits. The notochord is replaced by a cartilaginous or bony vertebral column in the adult in subphylum vertebrata.

Complete answer:
We say all vertebrates are chordates but all chordates are not vertebrates. Besides the basic chordate characters, vertebrates have a ventral muscular heart with two, three or four chambers, kidneys for excretion and osmoregulation and paired appendages which may be fins or limbs.

Now let us match this with given options :-
> Cartilaginous endoskeleton :- The Pisces are divided into two parts osteocytes and chondrocytes . Osteocytes are fishes that have bony endoskeleton and chondrocytes have skeletons composed of cartilage.

> Viviparous :- the organisms which directly produce young one are called viviparous and those that lay eggs are called oviparous. All the mammals are viviparous but ornithoranchus is a mammal that produces eggs.

> Posses a mouth with an upper and lower jaw :- all the chordates do not have both the jaw. Some have suctorial mouth as for instance cyclostomes and in some jaws are modified into beak as in birds.

> 3- chambered heart with incompletely divided ventricles :- reptiles are crawling organisms . They all have 3 chambered hearts but an exception is present that is crocodiles . Crocodiles have incompletely four chambered hearts.

Hence, the correct answer is option (A).

Note: Chondrocytes are the division of vertebrata . They are ectoparasites on other fishes . They are marine animals that have streamlined bodies. The notochord in these fishes are persistent throughout their life. Their mouth is located ventrally.