Phylum Chordata

All chordates are characterized by four features at different stages of their life:

• Notochord– It is a longitudinal, cartilaginous rod running between the nerve cord and the digestive track. It acts as a support for the nerve cord. In vertebrates, it is replaced by vertebral column after the embryonic stage.
• Dorsal nerve cord–It is a bundle of nerves which runs along the “back” and splits into the brain and the spinal cord
• Pharyngeal slits–They are the openings which allow the entry of water through the mouth without entering the digestive system i.e., they connect mouth and throat.
• Postanal tail–It is an extension of the body to the ****. In chordates, the tail is composed of skeletal muscles which help in locomotion in fish-like species.

Other features of chordates include:

• Bilaterally symmetrical, triploblastic, coelomic and segmented body.
• The body design is complex and well-differentiated.
• The body has organ system level of organization.