Difference Between Chordates and Non Chordates (original) (raw)

Last Updated : 23 Jul, 2025

**Difference between Chordates and Non-Chordates: **Chordates and **Non-Chordates are two groups of animals based on the presence or absence of a notochord. Notochord is a flexible rod-like structure that provides support. Chordates possess a notochord at some stage of their life. Non-chordates, on the other hand, lack a notochord. In this article, we will cover key distinctions between chordates and non-chordates in detail.

Difference Between Chordates and Non-Chordates

The difference between Chordates and non-chordates are as follows:

Features	Chordates	Non-Chordates
Notochord	Present at some stage; replaced by the vertebral column	Absent
Symmetry	Bilateral or radial	Radial, bilateral, or asymmetrical
Body temperature	Can be cold-blooded or warm-blooded	Cold-blooded
Coelom	True coelomates	Can be acoelomates, pseudocoelomates, or coelomates
Germ Layer	Triploblastic	Diploblastic or Triploblastic
Level of Organisation	Organ system	Protoplasmic to organ system
Post-anal tail	Present for body balancing	Absent
Skeleton	Endoskeleton present in all; exoskeleton in some	Exoskeleton present; endoskeleton absent
Regeneration	Poor	Good
Digestive system	Complete or incomplete	Often incomplete
Position of Gut	The gut is present ventral to the nerve cord.	The gut is present dorsal to the nerve cord.
Anus	Anus is differentiated and opens before the last segment.	Anus is generally absent. If present, it opens on the last segment.
Respiration	Aquatic species use gills; terrestrial use lungs	Diffusion across the body surface
Gill Slits	Pharynx is perforated by gill slits.	Gill Slits are absent
Circulatory system	Can be closed or open	Open circulatory system or no circulatory system
Heart	Ventral side	Absent or dorsally or laterally placed if present
Blood	Blood is red in colour due to the presence of hemoglobin.	Blood is colorless due to the absence of hemoglobin and is known as hemolymph.
Nerve cord	Single, dorsal nerve cord without ganglia	Double, ventral nerve cord with ganglia
Brain	Present dorsal to pharynx in the head	Present in some, but not as complex as in chordates
Examples	Tunicates, lancelets, vertebrates	Insects, mollusks, worms, jellyfish, and others

What are Chordates?

Chordates represent a diverse group of animals characterized by the presence of a notochord at some stage of their life cycle. The notochord serves as a support structure and is replaced by the vertebral column in vertebrates. Some invertebrates are also chordates because they have a notochord. But they lack a proper backbone and are thus called invertebrates. Those invertebrates which are included in chordates are tunicates and lancelets.

**Characteristics of Chordates

Chordates are considered one of the most advanced groups of animals, showing a high level of complexity and specialization:

They can be cold-blooded or warm-blooded.
They are true coelomates and triploblastic.
Post-anal tail is present for body balancing.
Exoskeleton is present in some chordates like tortoises while the endoskeleton is present in all.
The regeneration power of chordates is poor.
They possess a complete or incomplete digestive system.
The gut is present ventral to the nerve cord.
Aquatic chordates respire through gills, while terrestrial species utilize lungs.
Some chordates, such as amphibians, can also respire through their skin.

What are Non-Chordates?

Non-chordates refer to a group of those animals that lack a notochord. They include insects, mollusks, worms, jellyfish, and many others.

**Characteristics of Non-Chordates

Non-chordates exhibit a wider range of body symmetries compared to chordates:

They are cold-blooded.
They can be acoelomates, pseudocoelomates, and coelomates.
Also, their germ layer can be diploblastic or triploblastic.
Post-anal tail is absent.
Exoskeleton is present while the endoskeleton is absent.
The regeneration power of non-chordates is good.
They have a protoplasmic to organ system level of organization.
The gut is present dorsal to the nerve cord.
Anus is generally absent. If present, it opens on the last segment.
Respiration in non-chordates occurs through diffusion across the body surface.
Gill slits are absent.