Habit and habitat: Animals of this phylum are found in almost all habitats of the world. Some species live in the land. Among the aquatic chordates some live in fresh water and some in marine water. Many species are arboreal, desert dweller, polar, cave dweller and carsorial. Some members of phylum chordate are ectoparasite on other animals.
Through out life or only at the embryonic stage animals of the phylum chordata have four principal characteristics:
- Notochord: They have in the middle of the dorsal side of the body a soft. flexible. rod shaped, firm, un-segmented structure called notochord, throughout the life or only in the embryonic condition. In higher chordates, it.is replaced by bony vertebral column.
- Nerve cord: A single medium, hollow nerve cord on the dorsal side of the body is present.
- Throughout life or at any stage of the life-cycle there are lateral pharyngeal gill slits.
- In case of the aquatic chordate body behind the anus modified into a muscular tail which is the accssory organ of locomotion.
Example: Bufo melanostictus (Toad) Crocodylus porosus (saline water crocodile) Homo sapiens (Man) Bubo bubo (owl) Catla catla (catla fish) Ascidia (Ascidia) Scoliodon (shark) Tenualosa ilsha (Hilsa fish) Mus musculus (Small rat) Bandicota indica (Large rat).