Chordata is the most advanced animal phylum. Chordata are the most highly evolved multicellular animals. Theyare most adaptable,mostsuccessful and most widely distributed animals showing diversity of forms, habitsand habitat. Chordates are bilaterally symmetrical and metamerically segmented, triploblastic, coelomates with organ system level of body Organisation. All chordates have three features in common. They are the presence of notochord, dorsal hollow nerve cord, and presence of gill slits.
Phylum chordate is divided into three subphyla onthe basis of the fate of the notochord. They are Urochordata, Cephalochordata and Vertebrata
Urochordata are marine primitive chordates. The body is covered by aloose tough covering called tezt.The common urochordates are Ascidia, Salpa, Herdmania, Doliolum, Pyrrosoma, Botryllus, Oikopleura, Clona etc.
Cephalochordata are the marine prochordates.The head and cranium is absent. It is represented by a singlegenus Branchiostoma (amphioxus of lancelet).
Vertebrates are bilaterally symmetrical, coelomates,triploblastic, and segmented. They are grouped into 5 classes
1. Pisces- They are the class to which the fishes belong .
2. Reptilia- The members of Reptiliaare cold bloodedanimals, have scales.
3. Amphibia: They have no scales, have 3 chambered heart.
Examples: Frogs,Toads,and Salamanders.
4. Aves: They are warm blooded animals and have a four chambered heart.
Examples: Ardea,Columba, Corvus,Bubo,Alcedoetc.
5. Mammalia: They are warm blooded animals with four chambered heart. They have mammary glands.
Examples: Platypus, Echidna, Kangaroo, Man, Canis, Pteropus, Delphinus, Camelus