What is the Difference Between Chordates and Non-Chordates?

Difference between Chordates and Non- Chordates Overview

The classification of living things on Earth is known as the animal kingdom, or Kingdom Animalia. Based on their unique characteristics, members of this group are classified into several Genus, Families, Orders, Classes, and Phyla. One of the most crucial elements in animal taxonomy is whether an animal has a notochord on its body or not. It's important to remember that a notochord is a flexible rod-shaped structure formed of cartilage. Both the names "chordates" and "non-chordates" are used to refer to animals, and they each fall under a distinct phylum of the Animalia kingdom. The main distinction between chordates and non-chordates is that the former have a spinal cord or backbone in their body structure while the latter lack one.

Tabular Difference Between Chordates and Non- Chordates

The following table gives you all the difference between chordates and non- chordates based on various parameters.

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What are chordates and non-chordates?

Here is a detailed explanation of the key difference between chordates and non- chordates.

Chordates 

Four crucial characteristics that appear at various stages of the development of Chordata animals are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. It's vital to remember that some of these traits are only present in specific animals during the embryonic developmental phases. Here, the distinctive qualities of Chordates are briefly described.

Notochord

The notochord, which is the defining feature of chordates, is a stabilising, rigid rod-like structure. It provides skeletal stability and runs the entire length of the body, between the alimentary canal and the nerve cord. The notochord acts as the body's primary axial stiffness in some chordates. Vertebrate embryos frequently have the notochord, which promotes the development of the neural tube and serves as a framework for the developing embryonic structure. On the other hand, in the postnatal stage of vertebrates, the vertebral column or spine has taken the place of the notochord.

Dorsal hollow nerve

The dorsal hollow nerve cord, a component of chordates' central nervous systems, processes stimuli and nerve impulses. Ectoderm that develops into a hollow tube is the material that makes up the dorsal hollow nerve cord. In chordates, it is situated dorsally to the notochord. The nerve cord found in the majority of chordate embryos develops into the brain and spinal cord, which together make up the central nervous system.

Pharyngeal Gill

Gill slits are an essential component of the respiratory system that are perforated in the pharynx. Pharyngeal slits are openings in the pharynx that are visible from the outside. Pharyngeal apertures make it possible to remove water from the mouth during feeding. They can be observed in animals that live in aquatic settings. In vertebrates, the pharyngeal slits are changed into gill supports, and in fish with jaws, they become jaw supports.

Post Anal Tail

In chordates, the post anal tail appears as a brief extension at the end of the anus. The post-anal tail is a posterior portion of the body that extends past the anus. The tail of aquatic creatures like fish contains skeletal elements and muscles that help with movement. In some terrestrial species, the tail also serves in balance, courting, and warning of impending danger. Humans have a short, vestigial post-anal tail that serves no purpose.

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2. Non-Chordates

To better grasp the differences between chordates and non-chordates, let's take a quick look at some of their key characteristics. Animals without the notochord, a rod-like structure in their body, are known as non-chordates. This phylum mostly contains members of the phyla Porifera, Hemichordata, Echinodermata, Mollusca, Arthropoda, Annelida, Aschelminthes, Platyhelminthes, Ctenophora, and Coelenterata. Organ-system level organisation characterises this phylum.

The following list includes the general characteristics of non-chordates.

1. Typically cylindrical, triploblastic, coelomate, or pseudocoelomate describe non-chordates.
2. Non-chordate animals breathe through their gills, trachea, or skin.
3. Non-chordate members cannot be distinguished based on gender.
4. There are both sexual and asexual forms of reproduction.
5. While some species have internal fertilisation, fertilisation is external.
6. Body systems of non-chordates often feature an open circulatory system.

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Things to Remember

1. The animal kingdom, also referred to as Kingdom Animalia, is an important division of all surface-dwelling organisms. Depending on individual traits, members of this group are further divided into a variety of Genus, Families, Orders, Classes, and Phyla.
2. Animals classified as non-chordates do not have the notochord, a rod-like structure, in their body.
3. They are essentially cylindrical, triploblastic, pseudocoelomate, or coelomate organisms.
4. Animals with a notochord somewhere on their body are said to have chordates. Pharyngeal gill slits and a hollow nerve cord set this group apart.
5. The post-anal tail is a tiny protrusion that can be seen in chordates at the termination of the anus.
6. The primary distinction between the two is that ganglia are absent from the dorsal, hollow, and solitary nerve cord of chordates. In contrast, non-chordates have a central, significant, double nerve cord present, and their nerve cords contain ganglia.

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Conclusion

Chordates and non-chordates are primarily characterised by the presence or absence of the ectoderm, a crucial structure, at a specific point in their lives. Between these two groups of species, there are a number of differences. Some invertebrates are classified as chordates because they lack a backbone but yet preserve a vestige of a tail. Invertebrates categorised as chordates include tunicates and lancelets. Since Balanoglossus possesses characteristics shared by both vertebrates and non-chordates, it is believed to provide a link between these two groups. A characteristic of chordates is the pairing of the notochord with the pharyngeal gill slits in Balanoglossus, for instance.

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