question_answer 6)

How are animals in vertebrata further classified into sub-groups? Explain.        

Answer:

The subphylum vertebrata has been classified into two superclasses, namely, agnathaand gnathostomata, on the basis of presence or absence of jaws and paired appendages. Agnatha does not have jaws and paired appendages while gnathostomata bear jaws and paired appendages.                                                                     Superclasses have further been classified into Pisces, Amphibia, Reptilia,  Aves and Mammalia.                                                                      The major characteristics used to classify are — (i) The kind of exoskeleton or endoskeleton, (ii) The kind of respiratory organs, (iii) The method of reproduction and giving birth to young ones.                                                                    1.Exoskeleton of scales; Endoskeleton of cartilage or bones; Breathing through gills-Pisces (fishes). 2. Breathing through gills only in larva; Skin slimy - Amphibia.                      3. Exoskeleton of scales; Laying eggs outside the water-Reptilia.                      4. Exoskeleton of feathers; Lay eggs; Flight possible - Aves (Birds).                   5. Exoskeleton of hairs; External ears ; Give birth to young ones -Mammalia.