Difference between Chordates and Non-Chordates

Introduction

Chordates and non-chordates are the classification of organisms that exhibits their respective features. The two categories of organisms are different from one another based on their morphological traits and their course of sustenance. These organisms are primarily differentiated based on the presence of notochord at any stage of their lives. There are, however, several other differences in their respective physical features.

Chordates and Non-chordates: Overview

The presence and absence of notochord is quite a crucial component in the formation of the taxonomy of animals. The notochord is nothing but a cartilage-like structure that appears like a rubbery rod.

The chordates and non-chordates are associated with the animal kingdom; however, they belong to different phyla. The critical point of their differentiation lies in the presence of the backbone or spinal cord which primarily exists in the form of notochord. This substance is not found in the case of non-chordates.

In simple terms, chordates are the creatures that retain a dorsal hollow cord of nerves along with other substances like pharyngeal slits and post-anal tail. These components are found in the course of development of chordates. Some of these traits are only present only at the embryonic stage.

Non-chordates are creatures that do not have a notochord. Sponges are the most common example of non-chordates. Mollusca, Arthropoda and Annelida are all members of this particular phylum.

Features of Chordates

The notable features of chordates are as mentioned below.

• Notochord − Notochords are supportive rod-like structures. It is the most salient and distinct trait of all the chordates. This aspect runs through the length of the body that is found in the alimentary canal and the nerve cord and it gives stability to the skeletal system. This structure is highly prevalent in the vertebrates, especially in the developmental stage of an embryo. The notochord however is most naturally absent in post-natal stages. At maturity, this substance is replaced by the spine.

• Dorsal hollow nerve − It is a part of the central nervous system found in the chordates that are related to the impulses of the nerves. The nerve cord is made of ectoderm. This becomes a hollow tube as it progresses.

• Pharyngeal slits − These are integral parts of the respiratory system and it gets intersected with the gill slits found in marine creatures. The pharyngeal slits are the slits in the pharynx that opens on the external surface. It helps in the removal of water that has been consumed during feeding. These substances are evolved into gill supports for vertebrates and jaw supports for fishes that have jaws.

• Post-anal tail − The tail that is found at the terminal end of the anus of the chordates and it forms a short extension. A posterior exterior of the body that elongates beyond the anal region is termed post-anal tail. The post-anal tail is vestigial in humans and is non-functional.

Features of Non-chordates

Some of the notable features of non-chordates are as mentioned below.

• They are generally cylindrical in structure and are known to be triploblastic.

• They breathe through gills or surfaces on the body.

• The sexes of non-chordates cannot be differentiated.

• These organisms are capable of reproducing in both sexual and asexual modes

• The course of fertilization for these organisms mostly occurs in the external region. Some organisms however can fertilize the internal region.

• The non-chordates generally possess an open circulatory system.

Difference Between Chordates and Non-Chordates

The key differences between chordates and non-chordates are as mentioned below.

Parameters	Chordates	Non-chordates
Notochord	These organisms possess a notochord.	They do not have notochord.
Limbs	Mostly these organisms have two pairs of limbs	These creatures can have multiple pairs of limbs.
Heart	These creatures have a ventricle heart along with the presence of haemoglobin and RBC	The heart of these creatures is in the dorsal position.
Post anal tail	These organisms have a post-anal tail attached to their body.	Post-anal tail is absent in these organisms.
Nerve cord	A single dorsal and hollow nerve cord is present in these organisms and it is void of ganglia.	The nerve cord of non-chordates has ganglia.
Circulatory system	They have closed circulatory system.	They have open circulatory system.
Gill slits	Pharyngeal gill slits are found in these organisms.	The gill slits are absent in these organisms.
Exoskeleton	Exoskeleton is found in certain chordates.	Exoskeleton is found in all non-chordates
Endoskeleton	Endosketon is found in all chordates.	Endoskeleton is not found in non- chordates.

Conclusion

Chordates and non-chordates belong to different phyla of the animal kingdom. Both of these organisms possess the respective definitive traits that separate them from one another. However, the presence of notochord is the most identical factor that differentiates chordates from non-chordates. All of these organisms are highly abundant in nature and are crucial to animal taxonomy for their salient attributes.

FAQs

Qns 1. Are invertebrates included among chordates?

Ans. Yes, a handful of invertebrates falls under the classification of the chordates because of the presence of notochord. However, the invertebrates lack backbone. The most prominent example of these invertebrates includes tunicates and lancelets.

Qns 2. What is the sub classification of chordates?

Ans. Chordates can further be differentiated between urochordates, cephalochordates and vertebrates. Vertebrates are further categorised into Agnathostomes and Gnathostomes. The gnathostomes can either be fishes or tetrapods based on the structure of locomotion.

Qns 3. What are some salient features of the brain and organisation in chordates and non-chordates?

Ans. Chordates have a brain and are found dorsal to the pharynx in the head. They have complex brain structures and functions. The brain in non-chordates is not as complex as that of the chordates. These organisms have a well-structured organ system. The body structure of the non-chordates is protoplasmic.