Chordata:

Organization: Organ level

Symmetry: Bilateral

Coelom: present (coelomates)

Segmentation: Present

Arrangement of embryonic layers: Triploblastic

Digestive system: Complete

Circulatory system: Present

Respiratory system: Present

Habitat:  May be aquatic, marine, or even terrestrial.

Sexuality: Dioecious (sexes are separate).

 Notochord: Present

 Reproduction: Sexual (oviparous and viviparous both).

Fertilization: Varies to a large extent:

•  Cyclostomata , Osteichthyes and Amphibia→ external, oviparous
•  Chondrichthyes and Mammalia → internal, viviparous
• Aves and Reptilia→ internal, oviparous 

Respiratory organs: gills, lungs, skin etc.

Distinctive features:

Phylum chordate is divided into three sub-phyla:

• Urochordates→ They are known as proto-chordates. They are marine and notochord is present only in larval tail.
•  Cephalochordates→ They are also known as proto-chordates.They too are marine but notochord is present throughout their life.
•  Vertebrates→ They possess notochord during the embryonic period. The notochord is replaced by a cartilaginous or bony vertebral column in the adult.

*Justify why, all vertebrates are chordates but all chordates are not vertebrates.

It is quite that chordates have notochord. Whereas, Urochordates have notochord present only in larval tail, Cephalochordates have notochord persistant throughout their life. But in vertebrates, notochord is present only during the embryonic period, after that it is replaced by a cartilaginous or bony vertebral column in the adult. So, all vertebrates are chordates but all chordates are not vertebrates.

The sub-phylum Vertebrata is further divided into:

1) Agnatha (jaw less): It is further divided into class Cyclostomata.

2) Gnathostomata (having jaws): It is further divided into two super-classes, pisces and tetrapoda.Members of Pisces bear fins and  is further divided into two classes; Condrichthyes and Osteichthyes. Members of Tetrapoda bear limbs and is further divided into four classes; Amphibia, Reptilia, Aves and Mammalia.