Question

Distinguish between Chordates and Non-chordates.

Hint:

Remember the four hallmark chordate features: notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail.

Answer 1

Chordates and non-chordates can be distinguished by the presence or absence of key structural features at some stage of development. Major distinguishing characters are listed below.

Feature	Chordates ; Non-chordates
Notochord	Present at some stage ; Absent
Dorsal hollow nerve cord	Present ; Usually ventral solid nerve cord or diffuse nerve net
Pharyngeal gill slits	Present at some stage ; Absent or modified differently
Post-anal tail	Present at some stage ; Absent or not persistent
Segmental arrangement	Myotomes and segmented muscles usually present ; Segmentation variable or absent
Endoskeleton	Often present (cartilage or bone) ; Usually absent or present as exoskeleton
Circulatory system	Closed in many chordates ; Usually open or more variable in non-chordates
Cephalization and advanced organ systems	Well developed (brain, sensory organs) ; Less specialized in many non-chordates

 

Summary statement: Chordates are defined by the notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail appearing at some stage of life, whereas non-chordates lack this specific combination of features and show greater diversity in body plans and organ-system organization.