Difference Between Chordates and Non Chordates in Biology

The animal kingdom, sometimes known as Kingdom Animalia, is a well-known categorization of living organisms on Earth. Members of this group are divided into a variety of Genus, Family, Order, Class, and Phyla based on their individual traits. The presence or absence of a notochord on an animal's body is one of the most important factors in animal taxonomy. It's worth noting that a notochord is made of a cartilage-like structure and looks like a flexible rod. Chordates and Non-chordates, both the terms are used for animals and they belong to the different phyla of the Animalia kingdom. The major point to differentiate between chordates and non-chordates is that chordates have a spinal cord or backbone in their body structure whereas non-chordates are without backbone or notochord in their body structure.

The article discusses the different parameters based on which chordates and non-chordates are differentiated. The article also encompasses the description of chordates and non-chordates.

Chordates 

A notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail are four important traits that arise at some point during the development of Chordata animals. It is important to note that some of these characteristics are present only in embryonic developmental stages in some of the animals.  The characteristic features of Chordates are discussed briefly below.

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Notochord

The notochord is a supportive, stiff rod-like structure which is the characteristic of chordates. It runs the length of the body, in between the alimentary canal and the nerve cord, and provides skeletal stability. In certain chordates, the notochord serves as the body's major axial rigidity. The notochord is prevalent in vertebrates in embryonic developmental stages, where it stimulates neural tube formation and acts as a framework for the growing embryonic structure. The notochord, on the other hand, is absent in the postnatal stage of vertebrates; this has been substituted by the vertebral column or spine.

Dorsal hollow nerve-

The dorsal hollow nerve cord is part of the Central Nervous System of chordates and it is concerned with stimulus and nerve impulses. The dorsal hollow nerve cord is made up of ectoderm that becomes a hollow tube as it develops. It is located dorsally to the notochord in chordates. Most chordate embryos have a nerve cord that grows into the brain and spinal cord, which make up the central nervous system.

Pharyngeal gill-

Pharyngeal gill slits are an important part of the respiratory system and it gets perforated with gill slits. Slits in the pharynx that open externally are known as pharyngeal slits. Pharyngeal slits enable the removal of water that is engulfed into the mouth during feeding.  They are seen in creatures that dwell in aquatic habitats. The pharyngeal slits are transformed into gill supports in vertebrates and jaw supports in jawed fishes. 

Post anal tail- 

Post anal tail is present at the end of the anus in chordates in the form of a short extension. A posterior extension of the body that extends beyond the anus is known as the post-anal tail. In aquatic organisms like fishes, the tail comprises skeletal structures and muscles that facilitate movement. The tail also aids balance, courtship, and alerting when danger is approaching in certain terrestrial animals. The post-anal tail is vestigial in humans, meaning it is small and nonfunctional.

Non-chordates

Let us look briefly into the important features of non-chordates for a better understanding of the differences between the chordates and non-chordates. Non-chordates are creatures that lack the notochord, a rod-like structure in their bodies. Members of the phyla Porifera, Hemichordata, Echinodermata, Mollusca, Arthropoda, Annelida, Aschelminthes, Platyhelminthes, Ctenophora, and Coelenterata are predominantly found in this phylum. This phylum is organised on an organ-system level.

The general features of the non-chordates are mentioned below.

• Non-chordates are generally cylindrical, triploblastic, coelomate, or pseudocoelomate.

• Non-chordates breathe through the gills, trachea, or the surface of their bodies.

• The sexes of the members of non-chordates cannot be differentiated.

• Both sexual and asexual reproductive modes exist.

• Fertilization is external, while some species have internal fertilisation.

• Non-chordates' bodies usually have an open circulatory system.

Difference between chordates and non-chordates

Here is the tabular structure to highlight the differences and students will get an easy understanding to distinguish between chordates and non-chordates in their examinations.

Distinguish Between Chordates and Non-Chordates

In conclusion, we have learnt about the differences between the two important classifications of the animal kingdom. We have also learnt about the parameters of differentiation.