Difference between Chordates and Non-Chordates

Learn about the key distinguishing features between chordates and non-chordates with this informative article. Explore the unique characteristics of both groups and gain a deeper understanding of the fascinating world of animal diversity.

Introduction

Classification of animals is one of the essential areas of research in biology. The classification is based on the characteristics of the animal, and the most commonly used classification is based on the presence or absence of a notochord, which divides animals into two groups: chordates and non-chordates. This blog post will explore the differences between these two groups of animals and their characteristics.

What is notochord?

The notochord is a structure found in the early embryos of all chordates, which includes vertebrates (animals with a backbone) as well as some invertebrate groups. It is a flexible, rod-shaped structure that runs along the length of the embryo, just dorsal to the gut.

The notochord plays an important role in the development of the nervous system and axial skeleton. It helps to provide support and structure to the developing embryo, and also serves as a signaling center for the formation of surrounding tissues.

In some vertebrates, such as humans, the notochord is eventually replaced by the vertebral column (or backbone) during development. However, remnants of the notochord persist in the adult as the nucleus pulposus, which is the gel-like center of the intervertebral discs that cushion the vertebrae.

Characteristics of Chordates

The notochord is a key characteristic that defines chordates. It is a flexible rod that runs the length of the animal’s body, supporting it and providing attachment points for muscles. In chordates, the notochord is replaced by the vertebral column in most adults. Another defining characteristic is the dorsal hollow nerve cord, which runs along the back of the animal and gives rise to the central nervous system. Chordates also have pharyngeal slits or pouches, which are openings in the pharynx that are used for feeding and breathing. Lastly, chordates have a post-anal tail, which extends beyond the anus and is used for movement.

Characteristics of Non-chordates

In contrast, non-chordates lack a notochord and instead have a dorsal solid nerve cord. They also do not have pharyngeal slits or pouches or a post-anal tail. These animals are divided into various groups based on their body symmetry, circulatory system, and respiratory system.

Difference between Chordates and Non-Chordates

Feature	Chordates	Non-Chordates
Notochord	Have a notochord	Do not have a notochord
Nervous system	Have a dorsal hollow nerve cord	Have a nerve net or simple nerve cord
Symmetry	Bilateral or radial symmetry	Radial, bilateral or asymmetrical
Circulatory system	Have a closed circulatory system	Have an open or no circulatory system
Respiratory system	Have gills or lungs for gas exchange	Simple diffusion through skin or gills
Digestive system	Have a complete digestive system	Have an incomplete digestive system
Reproductive system	Have separate sexes or hermaphroditic	Hermaphroditic or asexual
Skeletal system	Have an endoskeleton or exoskeleton	May have an exoskeleton or no skeleton
Habitat	Can be found in aquatic or terrestrial environments	Can be found in aquatic, terrestrial or aerial environments
Body size	Range from very small to very large	Range from very small to moderately large
Evolutionary history	Evolved from invertebrate ancestors	Includes diverse invertebrate groups
Examples	Fish, amphibians, reptiles, birds, mammals	Insects, mollusks, arachnids, annelids, sponges

Examples of Chordates and Non-chordates

Chordates include fish, amphibians, reptiles, birds, and mammals. Non-chordates are a diverse group that includes sponges, cnidarians, flatworms, annelids, arthropods, mollusks, and echinoderms.

Conclusion

The differences between chordates and non-chordates are significant and based on their unique characteristics. Understanding these differences can help researchers classify and identify new animal species. Additionally, understanding these differences can help individuals appreciate the diversity of the animal kingdom and the complexity of the natural world.

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