Difference Between Chordates and Non Chordates

The key difference between chordates and non chordates stems from the presence and absence of a notochord. Chordates are organisms with a distinct notochord developed into vertebral column. In contrast, non chordates are organisms that do not have a notochord or a vertebral column.

Chordates and non chordates are two phyla that belong to the kingdom Animalia. They are characterized based on primary evolutionary characteristics. Upon evolution, animals developed a notochord which made them Chordates.

CONTENTS

1. Overview and Key Difference
2. What are Chordates 
3. What are Non Chordates
4. Similarities Between Chordates and Non Chordates
5. Side by Side Comparison – Chordates vs Non Chordates in Tabular Form
6. Summary

What are Chordates?

Chordates or vertebrates have four main features that distinguish them from non chordates. These features show up at some stage of the life cycle of chordates. Those four main features are;

1. Notochord
2. Pharyngeal slits, which are also called gills
3. Dorsal nerve cord which develops into nervous system and brain
4. Post-anal tail

There exist three main subphyla of chordates; they are:

1. Vertebrata – Animals belonging to the classes Pisces, Aves, Reptilia, Amphibia and Mammalia belong to this group.
2.  Cephalochordata or Lancets – Animals that have prominent cephalization.
3.  Urochordata – Animals that have a prominent tail or a post-anal. Organisms such as sea squirts belong to this group.

What are Non Chordates?

Non chordates, also known as invertebrates, do not have a notochord or a vertebral column. Moreover, this group includes a large number of organisms on earth.

Non Chordates are classified further into phyla:

1.  Porifera – Sponges belong to this group. They are the most primitive invertebrates.
2.  Cnidaria – Aurelia, Hydra, etc. belong to this group. They are diploblastic animals with radial symmetry
3.  Platyhelminthes – Triploblastic flatworms
4.  Nematoda – Roundworms which are triploblastic and bilaterally symmetrical
5.  Annelida – Triploblastic organisms with segmented bodies. Examples: Nereis
6.  Mollusca – They have a characteristic outer covering/shell. Examples: Chiton, Octopus
7.  Arthropoda – Their bodies are highly segmented, and most insects belong to this group.
8.  Echinodermata – Mostly marine organisms which are pentaradially symmetrical Examples: Sea lily, starfish.

What are the Similarities Between Chordates and Non Chordates?

• Both belong to the Kingdom Animalia.
• They are both multicellular organisms.
• Both have a nerve cord.

What is the Difference Between Chordates and Non Chordates?

Summary – Chordates vs Non Chordates

In general, chordates and non chordates are distinguished based on the presence and absence of a notochord. Chordates have a prominent notochord, whereas non chordates do not have a notochord. It is the key difference between chordates and non chordates. In addition to this main feature, other features such as nerve cord, post-anal tail, and pharyngeal slits can also be used to distinguish between the two groups.

Reference:

1. Ghiselin, Michael T. “Chordate.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 22 Nov. 2017, Available here.
2. “Invertebrates.” Biology@TutorVista.com, Available here.

Image Courtesy:

1. “The chordates (1950) (20618085901)” By Internet Archive Book Images – (No restrictions) via Commons Wikimedia
2. “Purple Cup Sponges” By icelight  (CC BY 2.0) via Commons Wikimedia