Inside Biology

Diving Deep into the Enigmatic World of Chordates: Evolution & Diversity

Title: Exploring the Fascinating World of Chordates: From Phylum to SubphylaHave you ever wondered what sets humans apart from other animals? Why is it that we possess certain unique characteristics?

The answer lies in our classification as chordates, a diverse group of animals with a distinct set of defining features. In this article, we will take a deep dive into the world of chordates, exploring their characteristics and the three subphyla they belong to.

Join us on this educational journey as we unravel the mysteries of chordates and their incredible diversity.

Chordates and their Characteristics

Phylum Chordata and Deuterostomes Kingdom

Chordates belong to the phylum Chordata, one of the major animal phyla. What makes chordates unique is their classification as deuterostomes, which means that during embryonic development, the anus develops before the mouth.

This key characteristic sets them apart from protostomes, where the mouth forms before the anus. Furthermore, chordates are classified under the Deuterostomes Kingdom, which includes a variety of animals with radial cleavage, indeterminate growth, and the presence of coelom.

Characteristics of Chordates

Chordates possess a remarkable set of characteristics that distinguish them from other animals. These include:


Anus develops before mouth: As mentioned earlier, chordates are deuterostomes, which means that their anus forms before the mouth during embryonic development. This unique feature sets them apart from protostomes, showcasing their evolutionary divergence.

2. Pharyngeal slit: Another defining characteristic of chordates is the presence of pharyngeal slits.

These slits, located in the pharynx, serve a variety of functions in different chordates, such as respiration, filter-feeding, or even sound production. 3.

Dorsal hollow nerve cord: Chordates possess a dorsal hollow nerve cord that runs along their back, adjacent to the notochord. This nerve cord serves as the central nervous system, controlling and coordinating various bodily functions.

4. Notochord: The notochord, a flexible rod-like structure, runs along the length of a chordate’s body.

It provides support and enables efficient muscle attachment, aiding in locomotion. 5.

Post-anal tail: Chordates possess a tail that extends beyond the anus, known as the post-anal tail. This tail enables balance and efficient movement, especially in aquatic species.

Three Subphyla of Chordata

Subphylum Vertebrata/Craniata

The largest and arguably the most well-known subphylum of chordates is Vertebrata, also known as Craniata. Vertebrates are characterized by the presence of a vertebral column or spine, which supports and protects the delicate spinal cord.

Another distinguishing feature of vertebrates is the presence of a well-developed skull that houses the brain, providing additional protection. This subphylum includes familiar animals such as fish, amphibians, reptiles, birds, and mammals.

Subphylum Cephalochordata/Lancelets

Within the chordates, we find the fascinating subphylum Cephalochordata, commonly known as lancelets. These small, elongated marine creatures may not be as well-known as their vertebrate relatives, but they possess unique characteristics.

Lancelets exhibit filter-feeding behavior, using their pharyngeal gill slits to extract plankton from the water. They lack a true vertebral column but possess a notochord that extends the length of their bodies, providing structure and support.

Subphylum Urochordata/Tunicates

Last but not least, we have the subphylum Urochordata, commonly known as tunicates or sea squirts. Tunicates, although seemingly different from other chordates, share several defining features.

In their larval stage, tunicates possess characteristics seen in other chordates, such as a notochord, a dorsal hollow nerve cord, and pharyngeal gill slits. However, during their adult stage, they undergo metamorphosis, where most of these features are reduced or lost.

Tunicates are filter-feeding organisms, drawing water in through their incurrent siphons and expelling it through their excurrent siphons. Conclusion:

In this article, we have explored the captivating world of chordates and their remarkable diversity.

We have learned about their unique characteristics, including the development of the anus before the mouth, the presence of pharyngeal slits, the dorsal hollow nerve cord, the notochord, and the post-anal tail. Additionally, we have delved into the three subphyla of chordates: Vertebrata/Craniata, Cephalochordata/Lancelets, and Urochordata/Tunicates.

Each subphylum presents its own set of intriguing adaptations and evolutionary paths. Chordates truly represent the epitome of evolutionary success and exemplify the dazzling variety of life on Earth.

Examples of Chordates


One of the fascinating examples of chordates is the lamprey, a type of jawless fish that belongs to the class Agnatha. Lampreys have a unique life cycle that involves a parasitic adult stage and a filter-feeding larval stage.

Let’s take a closer look at these intriguing creatures. Lampreys are known for their eel-like appearance, with a slender body and smooth, scaleless skin.

Unlike most fish, lampreys lack a true jaw. Instead, they possess a circular, sucker-like mouth filled with sharp teeth.

This specialized mouth allows them to attach to their prey and feed on their blood or bodily fluids. As parasitic adults, lampreys often attach themselves to other fish, using their mouth to create a small puncture wound from which they feed.

However, lampreys begin their lives in a completely different manner. As larvae, they are filter-feeders, using their well-developed pharyngeal gill slits to extract microscopic organisms and organic matter from the water.

This early stage of their life cycle is spent in freshwater streams or rivers, where lamprey larvae actively swim and search for food. Filter-feeding in the larval stage allows lampreys to accumulate nutrients needed for growth and development.

As lampreys transition from larvae to adults, they undergo a remarkable physiological change. They develop a muscular, sucker-like mouth, and their digestive system adapts to parasitic feeding.

This switch in feeding behavior also coincides with their migration to the ocean, where they spend most of their adult lives. Despite their predatory nature as adults, lampreys do not possess jaws or true teeth, relying solely on their sucker-like mouth to latch onto their prey.

Sea Squirts

Another intriguing example of chordates is the sea squirt, also known as tunicates or ascidians. Sea squirts belong to the subphylum Urochordata and are renowned for their unique barrel-shaped bodies.

Let’s delve into the world of these filter-feeding marine organisms. Sea squirts possess a soft, sac-like body covered by a tough outer covering called the tunic.

The tunic gives them their common name and offers protection from predators and the abrasive forces of the ocean. Despite their simple appearance, sea squirts exhibit incredible adaptability and resilience, making them a diverse and widespread group of marine organisms.

As filter-feeders, sea squirts draw in water through their incurrent siphon, which acts as an intake tube. The water then passes through a specialized structure called the pharynx, where microscopic food particles are filtered and consumed.

The filtered water is then expelled through an excurrent siphon, completing the filter-feeding process. Sea squirts come in a variety of shapes, sizes, and colors.

Some types form colonies, with individual sea squirts connected by a common tunic. These colonies can take on magnificent and elaborate forms, ranging from encrusting mats to towering structures.

One of the intriguing aspects of sea squirts is their ability to undergo metamorphosis during their life cycle. In their larval stage, sea squirts possess a notochord, a dorsal hollow nerve cord, and pharyngeal gill slits, all of which are characteristic of chordates.

However, as they grow into adults, most of these features become reduced or lost. This unique transformation, called retrogressive metamorphosis, sets them apart from other chordates.

Despite losing these chordate characteristics, sea squirts retain their identity as members of the chordate phylum. In conclusion, the examples of lampreys and sea squirts showcase the remarkable diversity within the chordate phylum.

Lampreys, with their jawless mouths and parasitic feeding habits, demonstrate the exceptional adaptability of chordates in different life stages. On the other hand, sea squirts, with their barrel-shaped bodies and filter-feeding behavior, highlight the astonishing ability of chordates to undergo metamorphosis while still retaining their essential chordate characteristics.

These examples serve as a testament to the captivating world of chordates and their endless wonders. Word Count: 1010.

In conclusion, chordates, with their distinguishing characteristics and diverse subphyla, showcase the fascinating world of animal evolution. From the development of the anus before the mouth to the presence of pharyngeal slits, dorsal hollow nerve cords, notochords, and post-anal tails, chordates represent an incredible variety of life forms.

The subphyla explored, including the vertebrates/craniates, cephalochordates/lancelets, and urochordates/tunicates, each contribute their own unique adaptations and evolutionary paths. Lampreys, with their jawless mouths and alternating parasitic and filter-feeding lifestyles, offer insight into the versatility of chordates.

Sea squirts, through their retrogressive metamorphosis and filter-feeding strategies, exemplify the latent chordate characteristics within their subphylum. This exploration of chordates encourages us to appreciate the diversity of life on Earth and the continuous evolutionary adaptations that have shaped our world.

By understanding chordates, we gain a deeper understanding of our own place within the animal kingdom and the incredible complexity of life. Embrace the wonders of chordates and let their diversity inspire our curiosity and awe for the natural world.

Popular Posts