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Example of Chordata
Are animals with notochord, dorsal tubular nerve cord and paired pharyngeal slits. It is divided into three Sub Phyla.
Urochordata with notochord in the tail of the larva, which undergoes retrogressive metamorphosis.
Example: Ascidia, Herdmania
Cephalochordata notochord extends beyond the nerve cord in the head.
Example: Amphioxus or Branchiostoma
Notochord is replaced by vertebral column. It is divided into seven classes.
Class 1: Agnatha
Includes primitive jawless vertebrates with circular suctorial mouth.
Example: Petromyzon Lamprey (Order Cyclostomata).
Class 2 Chondrirchthyes
includes cartilaginous fishes with placoid scales, five pairs of gill slits, heteroceral tail fin
Example: Shark and rays
Class 3 Osteichthyes
includes bony fishes with dermal scales, four pairs of gill slits, two chambered venous heart etc.
Example: Hoplochilus and Gambusia are larvivorous.
Class 4 Amphibia
Includes animals with double life. Larvae are aquatic and adults are terrestrial or both. Skin is smooth, glandular and permeable. Heart is three chambered and larva is tad pole
Example: tailless frogs and toads, tailed salamanders and newts and limbless Icthyophis and Gegenophis.
Class 5 Reptilia
includes true land vertebrates. Skin is dry and scaly, respiration pulmonary, heart is three or four chambered, eggs are large, shelled and cleidoic. During development; the embryo is protected by membranes like amnion, chlorion, allantois and yolk sac.
Examples: Lizards, snakes, tortoise, crocodiles. Etc.
Class 6 Aves
includes birds, the areal vertebrates. They have feathers, pneumatic bones, air sacs, wings, high metabolic rate, constant body temperature etc. Most of the birds are flying birds. A few like Ostrich, Cassowary, Kiwi, Rhea etc are fight less
Class 7 Mammalia
Important characters are mammary glands, hairy, sweat and sebaceous glands, well developed brain, four chambered heart, warm-blooded nature etc. Viviparous. They exhibit parental care. Divided into three sub classes.
- Prototheria 2. Metatheria 3. Eutheria
Prototheria includes egg laying mammals like platypus and Echidna.
includes pouched mammals like Kangaroo.
The true placental mammlas, like rabbit, bet, whale, man