Question

Name three subphyla of phylum Chordata. Write characters and examples of Protochordates.

Answer 1

Hint: Animals are classified as Non-chordates and Chordates based on the absence and presence of Notochord. Chordates are further divided into three phyla. The Notochord is a skeletal rod that is made up of cartilages. ('Chorde' means cord and 'ata' means bearing).

Complete answer:
Kingdom Animalia consists of Phylum Non-chordates and Phylum Chordates. There are many differences between these two phyla. The differences are:
a) Non-chordates do not have Notochord while Chordates have Notochord
b) Non chordates show the presence of a Ventral Nerve cord while Chordates have dorsal nerve cord.
c) The Heart is dorsal in Non-chordates and ventral in Chordates
d) Pre-anal tail is absent in Non-chordates and seen in Chordates.

Chordates are thus advanced animals. This phylum is further divided as Protochordates and Vertebrates based on the absence and presence of the Vertebral column.
Protochordate are Craniates is brain box or cranium is absent. This is further divided into sub-phyla Urochordata and Cephalochordata. Urochordates have notochord only in the tail region. In cephalochordates, the notochord extends from head to tail region. Examples of urochordates are Ascidia, Salpa, and Doliolum. Examples of Cephalochordates are Branchiostoma.
Craniates are Vertebrates as in these animals Notochord is replaced by the Vertebral column which is more flexible than Notochord. Vertebrates are further classified as Agnatha and Gnathostomata based on absence and presence of jaws. Agnatha lack jaws and thus have circular mouths. Example : Cyclostomata. Gnathostomata includes Pisces, Amphibia, Reptilia, Aves, and Mammalia. Examples of Pisces are all fishes. Amphibia include frogs, salamanders etc. Reptiles are snakes, lizards etc. Aves are birds and Mammals are dogs, cats, men, etc.

Note: Many times students get confused between notochord and nerve cord. The Notochord is related to the skeletal system. It is absent in Non-chordates and present in Chordates. Nerve cord is related to Nervous system. It is present in all animals however, its position is different. In Non-chordates it is Ventral and in Chordates it is dorsal.