Animals belonging to phylum Chordata are fundamentally characterized by the presence of a notochord, a dorsal hollow nerve cord, and paired pharyngeal gill slits.
These are bilaterally symmetrical, triploblastic, and coelomate with the organ-system level of organization.
They possess a post-anal tail and a closed circulatory system.
Phylum Chordata is divided into three subphyla:
All living members of the class Cyclostomata are ectoparasites on some fishes.
Examples: Petromyzon (Lamprey) and Myxine (Hagfish).
They are marine animals with streamlined bodies and have cartilaginous endoskeletons.
The heart is two-chambered (one auricle and one ventricle).
Examples: Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), and Trygon (Sting ray).
It includes both marine and freshwater fishes with a bony endoskeleton.
Examples: Marine – Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater – Labeo (Rohu), Catla (Katla), Clarias (Magur); Aquarium – Betta (Fighting fish), Pterophyllum (Angelfish).
Amphibians can live in aquatic as well as terrestrial habitats.
Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibian).
The class name refers to their creeping or crawling mode of locomotion.
Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator). Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper).
The characteristic features of Aves (birds) are the presence of feathers and most of them can fly except flightless birds (e.g., Ostrich).
Examples: Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture).
They are found in a variety of habitats – polar ice caps, deserts, mountains, forests, grasslands, and dark caves.
Examples: Oviparous-Ornithorhynchus (Platypus); Viviparous - Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion).