Difference Between Chordates and Non-chordates

Difference Between Chordates and Non-chordates: Chordates v/s Non Chordates

Edited By Irshad Anwar | Updated on Jul 02, 2025 06:08 PM IST

According to Animal Kingdom Classification, Chordates and Non-Chordates are two major groups of animals that are differentiated by the presence or absence of a notochord. Chordates are animals that possess a notochord, a dorsal nerve cord, pharyngeal slits, and a post-anal tail at some stage of their development. Non-chordates lack these features and include a wide variety of animals such as sponges, insects, and molluscs. The difference between Chordata and Non-Chordata, Chordata (notochord present) and Non-Chordata (notochord absent), is based on the presence or absence of fundamental features like notochord, dorsal nerve cord, pharyngeal slits, and post-anal tail during any stage of development.

This Story also Contains

Differences Between Chordates and Non-Chordates
What are Chordates?
What are Non-Chordates?
Evolutionary Advantage in Chordates
Reproductive Strategies in Chordates and Non-Chordates

Difference Between Chordates and Non-chordates: Chordates v/s Non Chordates

The chordata group includes animals like Fish, Amphibians, Reptiles, Birds, and Mammals. In this article, Chordates and Non-Chordates, and the structural and physiological differences between them, are discussed. Chordates and Non-chordates are a topic of the chapter Animal Kingdom in Biology.

Differences Between Chordates and Non-Chordates

The table below shows the difference between chordates and non-chordate organisms. Explore more Differences and Comparisons Articles in Biology to deepen knowledge of key concepts.

Feature	Chordates	Non-Chordates
Notochord	Present (at least in one stage of the lifecycle)	Absent
Blood Temperature	Can be cold-blooded or warm-blooded	All are cold-blooded.
Mode of Respiration	Through lungs or gills.	Respire through tracheae, gills, or body surface.
Haemoglobin	Present in Erythrocytes	Absent, hemolymph may be present as a blood analogue.
Germ Layers	Triploblastic (three germ layers).	Can be triploblastic, diploblastic, or neither.
Symmetry	Bilaterally symmetric.	Can be bilateral, radial, bi-radial, or asymmetrical.
Coelom	True coelomates.	True coelomates, acoelomates, or pseudocoelomates.
Post-anal Tail	Usually present.	Absent.
Exoskeleton	Present in some, e.g., tortoises.	Generally present.
Endoskeleton	Present.	Absent.
Regeneration	Limited regeneration capability.	Regeneration capability is generally good.
Nerve Cord	Dorsal, single, without ganglia.	Ventral, double, and often with ganglia.
Blood Circulation	Closed circulatory system.	Usually open circulation.
Anus	Differentiated and opened before the last segment.	May be absent or open at the last segment.
Brain	Well-developed and dorsal to the pharynx.	Present in some, but less developed.
Organisation	Organ-system level.	Protoplasmic to organ-system level.
Heart	Ventrally placed.	Absent or dorsally/laterally placed if present.
Examples	Mammals, birds, reptiles, fish, and amphibians.	Arthropods, molluscs, cnidarians, sponges.

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What are Chordates?

Phylum Chordata are animals which possess a notochord, pharyngeal slits and a tail which is post-anal during some period of embryonic development. There is the formation of a nerve cord, which in the case of vertebrates is known as the spinal cord; it creates a central nervous system. The notochord is also involved in support and is replaced in vertebrates by the vertebral column. Other functions of pharyngeal slits include feeding and gas exchange whereas the post-anal tail provides motion and stabilisation of the organism.

Chordates comprise the fishes, amphibians, reptiles, birds, mammals, and those organisms not having backbones, namely the tunicates and the lancelets. It is in the subphylum Vertebrata where animals have a backbone and such adaptations as gills in fish, extra wings in owls, etc.

The following summarises the difference between the major groups of Chordates:

Group	Characteristics
Fishes	Gills, scales, fins, lay eggs in water.
Amphibians	Moist skin, metamorphosis, and typically aquatic larvae.
Reptiles	Scales, lungs, and amniotic eggs are laid on land.
Aves	Feathers, wings for flight, lay hard-shelled eggs.
Mammals	Hair/fur, and mammary glands mostly give birth to live young.

What are Non-Chordates?

Non-chordates are a very large and diverse category of animals that never at any time in their life possess one or other of the chordate characteristics notochord, dorsal hollow nerve cord pharyngeal slits, part or all of a post-anal tail. However, they do present a rather diverse morphological plasticity in the type and organisation of body plans as well as physiological abilities. Non-chordates are many and diverse, including Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, and Arthropoda, among others.

Broad Classification into various Phyla

Porifera (Sponges): Sponges is a simple organism that has a permeable body that feeds with the help of water currents that help filter water.
Cnidaria: Have jellyfish, corals and sea anemones belong to the group of cnidarians and consists of stinging cells called cnidocytes.
Platyhelminthes: First, non-coelomate Bilateral, which consists of a flatworm with or without a notochord, that is endoparasitic, such as the tapeworm.
Annelida: Earthworm and leech with a body cavity or coelom but are segmented worms.
Mollusca: Animals that do not have a rigid body but have a stiff part of the body like shells; includes snails, clams, and squids.
Arthropoda: It contains the greatest number of species; insects, spiders, crustaceans, that generally have joint appendages, and an external covering known as the exoskeleton.

Examples

Sponges (Phylum Porifera): They are the earliest and the simplest form of filter feeders that have a porous body structure.
Jellyfish (Phylum Cnidaria): Coelenterates with appendages bearing cnidocytes such as nematocysts.
Flatworms (Phylum Platyhelminthes): Organisms which are soft-bodied and have bilateral symmetry such as those belonging to the phylum Platyhelminthes but not the echinoderms, parasitic organisms like tapeworms.
Insects (Phylum Arthropoda): Multitudes of well-coordinated members with entrenched segmented, hard outside covering and articulated extremities.
Crustaceans (Phylum Arthropoda): Legged sea and freshwater crustaceans with segmented external coats, such as crabs and other kinds of lobsters.

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Diversity among non-chordates.

Evolutionary Advantage in Chordates

Chordates, mainly the vertebrates, have a closed circulatory system, hence a well-developed heart. The heart’s chambers help to facilitate the division of oxygenated and deoxygenated blood, making oxygen delivery to tissues improve metabolism. Chordates and non-chordates exhibit diverse respiratory adaptations suited to their habitats:

Gills: Located in fishes and certain other animals such as molluscs and crustaceans gills are specialized organs of respiration in water.
Lungs: Present in the body of almost every tetrapod or terrestrial vertebrate, which includes amphibians, reptiles, birds and mammals, lungs are specific vital organs that take charge of the exchange of gases between the atmosphere and the blood.
Tracheal system: Some insects and certain other arthropods possess tracheal tubes that carry air directly to the tissues, increasing the effectiveness of the respiratory apparatus in terrestrial conditions.

The following summarises the difference between respiratory adaptations.

Group	Respiratory Structures
Fish (Chordates)	Gills for underwater respiration, a counter-current flow system for efficient oxygen extraction.
Amphibians (Chordates)	Gills in larvae, lungs and skin for adults; buccal pumping for ventilation.
Reptiles (Chordates)	Lungs for respiration, some species have modified structures (e.g., crocodilians have hepatic-piston lungs).
Birds (Chordates)	Lungs supplemented by air sacs for efficient unidirectional airflow; high metabolic demands for flight.
Mammals (Chordates)	Lungs with alveoli for efficient gas exchange, diaphragm aids in breathing.
Insects (Non-chordates)	A tracheal system with air-filled tubes extending throughout the body, and spiracles for gas exchange.
Molluscs (Non-chordates)	In aquatic species (e.g., bivalves, gastropods), the mantle cavity aids in gas exchange.

Reproductive Strategies in Chordates and Non-Chordates

Chordates and non-chordates have different reproductive strategies and embryonic development. Understanding the reproductive strategies in chordates and non-chordates helps explain how different animals ensure survival and growth. The reproduction and embryo development are listed below-

Reproductive Strategies

Chordates: Fertilization is found both in the external and internal types among chordates. Internal fertilization is typical for the majority of the terrestrial and some of the aqueous animals; reproductive organs are involved here.
Non-chordates: Many non-chordates employ external fertilization, whereby the eggs and sperm are released to the surroundings and fertilized. This strategy is widespread in water habitats, particularly in numerous offspring-producing species.

Embryonic development:

Chordates: Chordates’ embryonic development entails characteristic features such as a notochord at some point. Notochord is used as a supporting structure and a developmental signpost and is later replaced by the vertebral column in the case of vertebrates.
Non-chordates: Some of the substrate characteristics that separate the non-chordates from the chordates are that they do not undergo the development of a notochord at any one time in their life. However, they may pass through different life forms like the larvae that are found in insects like caterpillars that transform into butterflies, and tadpoles into frogs of the insects.

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Frequently Asked Questions (FAQs)

1. What are the key characteristics of chordates?

The chordates are sub-grouped based on the following features: the presence of a dorsal hollow nerve cord, a notochord or vertebral column, pharyngeal slits or pouches and a postanal tail at some stage of their development.

2. How do chordates differ from non-chordates in terms of body structure?

Chordates may have bilateral body plans and may or may not have segmentation while non-chordates in general may have radial or asymmetrical body plans and are non-segmented.

3. What are some examples of non-chordates?

Some of the non-chordates examples of phyla that are included are Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, and Arthropoda among others.

4. Why are chordates considered more advanced than non-chordates?

For this reason, chordates are seen as being of higher development than non-chordates, especially because of the presence of a centralised nerve cord, sophisticated sensory organs such as eyes and ears in many of the chordates and a greater level of behavioural efficiency as well as adaptability.

5. How do chordates and non-chordates differ in their reproductive strategies?

While external fertilisation is seen occasionally in chordates, internal fertilisation is faired more among the terrestrial ones. This is external fertilisation, this is because the majority of non-chordates lay their eggs in water hence fertilisation takes place in water.

6. What is difference between chordata and non- chordata?

The main difference between chordates and non-chordates lies in the presence or absence of a notochord, a flexible rod-like structure that provides support.

7. What is difference between notochord and vertebral column?

Notochord is a flexible rod present in all chordate embryos, while the vertebral column is a bony structure found only in vertebrates that replaces the notochord.

8. How do circulatory systems compare between chordates and non-chordates?

Chordates typically have a closed circulatory system with a ventral heart that pumps blood through vessels. Non-chordates may have open or closed circulatory systems, depending on the phylum. For example, arthropods have an open circulatory system where hemolymph (their blood-like fluid) flows freely in body cavities, while annelids have a closed system similar to chordates.

9. How does the respiratory system differ between chordates and non-chordates?

Chordates typically have complex respiratory systems, often involving lungs or gills that are closely associated with the circulatory system. Non-chordates show a wide variety of respiratory structures. For example, insects use a tracheal system of tubes, while many aquatic invertebrates use gills or their entire body surface for gas exchange. The complexity and efficiency of gas exchange generally increase in chordates.

10. What is the significance of pharyngeal gill slits in chordates?

Pharyngeal gill slits are a key characteristic of chordates, even though they may not be present in all adult forms. These structures are important for feeding and respiration in aquatic chordates. In terrestrial chordates, they often develop into other structures during embryonic development. Their presence in all chordates, even if only during early development, indicates a common evolutionary origin.

11. What is the difference in body fluid regulation between chordates and non-chordates?

Chordates typically have sophisticated systems for regulating body fluids, including complex kidneys and osmoregulatory mechanisms. This allows them to maintain a stable internal environment across a wide range of external conditions. Non-chordates often have simpler osmoregulatory systems. For example, freshwater protozoans use contractile vacuoles to expel excess water, while marine invertebrates may be osmoconformers, allowing their internal fluid concentration to match their environment.

12. How does the presence of a pharynx differ between chordates and non-chordates?

All chordates possess a pharynx with gill slits at some point in their life cycle, even if these structures are modified or lost in adult terrestrial forms. The pharynx plays a crucial role in feeding and respiration. While some non-chordates (like hemichordates) have a structure similar to a pharynx, most lack this specific organ. Instead, they may have other specialized feeding structures, like the radula in mollusks or the proboscis in nemerteans.

13. How does the presence of a vertebral column differentiate chordates from non-chordates?

While all chordates have a notochord at some point in their life cycle, most chordates (vertebrates) develop a vertebral column that replaces or surrounds the notochord. This bony or cartilaginous structure provides support and protection for the spinal cord. Non-chordates lack both a notochord and a vertebral column, relying on other structures for body support.

14. What is the difference in locomotion methods between chordates and non-chordates?

Chordates typically use their muscular post-anal tail and paired appendages for locomotion, often in conjunction with their vertebral column. Non-chordates exhibit a wide variety of locomotion methods. For example, cnidarians may use jet propulsion, mollusks might use a muscular foot, and arthropods use jointed appendages. These differences reflect the diverse body plans and habitats of these groups.

15. How does the presence of a coelom differ between chordates and non-chordates?

All chordates are coelomates, meaning they have a true body cavity (coelom) lined with mesoderm. Among non-chordates, there's more variation. Some, like annelids and mollusks, are also coelomates. Others, like flatworms, are acoelomates (lacking a body cavity), while nematodes are pseudocoelomates (having a partial body cavity). The presence and type of body cavity affect how organs are supported and how the body moves.

16. What is the difference in excretory systems between chordates and non-chordates?

Chordates have complex excretory systems, typically involving kidneys that filter blood and produce urine. Non-chordates have a variety of simpler excretory structures. For instance, planarians have flame cells, insects have Malpighian tubules, and earthworms have nephridia. These different systems reflect the varying complexity and evolutionary history of these groups.

17. What is the difference in cell specialization between chordates and non-chordates?

Chordates generally have a higher degree of cell specialization and tissue organization compared to most non-chordates. This results in more complex organs and organ systems. While some non-chordates (like arthropods) also show significant cell specialization, others (like sponges) have relatively simple cellular organization. This difference reflects the evolutionary trend towards increasing complexity in chordates.

18. How does the nervous system differ between chordates and non-chordates?

In chordates, the nervous system is characterized by a dorsal, hollow nerve cord that develops into the brain and spinal cord. Non-chordates typically have a ventral nerve cord, which is solid and may form ganglia (clusters of nerve cells) along its length. This fundamental difference in nervous system organization reflects the distinct evolutionary paths of these two groups.

19. How does the development of the nervous system differ between chordates and non-chordates?

In chordates, the nervous system develops from the ectoderm through a process called neurulation, forming a hollow neural tube that becomes the brain and spinal cord. In non-chordates, nervous system development varies. For instance, in arthropods, the ventral nerve cord develops from an infolding of the ectoderm, but it remains solid rather than hollow. This fundamental difference in development leads to the distinct nervous system structures in these groups.

20. What is the difference in sensory organ complexity between chordates and non-chordates?

Chordates generally have more complex and specialized sensory organs compared to most non-chordates. For example, the vertebrate eye is a highly sophisticated organ with multiple components. While some non-chordates also have complex sensory structures (like the compound eyes of insects), many have simpler sensory organs. This difference reflects the overall trend of increasing complexity in chordates.

21. How does the presence of a cranium differentiate some chordates from non-chordates?

Most chordates (specifically, craniates) possess a cranium, which is a bony or cartilaginous case that encloses and protects the brain. Non-chordates lack this structure. Even within chordates, not all members have a cranium (e.g., lancelets), highlighting the diversity within the chordate group and the evolutionary development of this protective structure.

22. What is the difference in body segmentation patterns between chordates and non-chordates?

In chordates, segmentation is most evident in the vertebral column, muscles (myomeres), and peripheral nerves. This segmentation is derived from embryonic somites. In segmented non-chordates, like annelids or arthropods, the entire body is divided into similar repeating units (metameres). This fundamental difference in segmentation patterns reflects the distinct evolutionary paths and body organizations of these groups.

23. What is the difference in embryonic development between chordates and non-chordates?

Chordates undergo deuterostome development, where the blastopore (the first opening in the embryo) becomes the anus, and the mouth forms secondarily. Most non-chordates are protostomes, where the blastopore becomes the mouth. This fundamental difference in early development has far-reaching consequences for the overall body plan and organization of these animals.

24. What is the difference in reproductive strategies between chordates and non-chordates?

While both chordates and non-chordates exhibit a range of reproductive strategies, chordates generally have more complex reproductive systems and often employ internal fertilization. Many chordates also exhibit parental care. Non-chordates show a wider variety of reproductive strategies, from the simple budding of hydra to the complex metamorphosis and colony formation in some insects. This diversity reflects the varied evolutionary pressures on different groups.

25. What is the difference in metamorphosis between chordates and non-chordates?

While some chordates undergo metamorphosis (e.g., amphibians), it's more common and often more dramatic in many non-chordate groups. For instance, insects may go through complete metamorphosis with distinct larval, pupal, and adult stages. In chordates, metamorphosis typically involves fewer drastic changes. This difference reflects the diverse life histories and adaptive strategies of these groups.

26. What is the difference in hormone production and endocrine systems between chordates and non-chordates?

Chordates have complex endocrine systems with numerous specialized glands producing a wide array of hormones. These hormones regulate various physiological processes. Non-chordates also produce hormones, but their endocrine systems are generally less complex. For example, insects use hormones for molting and metamorphosis, but their endocrine system is simpler than that of chordates.

27. How does the presence of a tail in embryonic development differ between chordates and non-chordates?

All chordates possess a post-anal tail at some point in their development, even if it's not present in the adult form. This tail is an extension of the body beyond the anus and contains part of the notochord and nerve cord. Non-chordates do not have a true post-anal tail, although some may have tail-like structures that serve different functions.

28. What is the main distinguishing feature between chordates and non-chordates?

The main distinguishing feature between chordates and non-chordates is the presence of a notochord at some point in their life cycle. Chordates have a notochord, which is a flexible rod-like structure that provides support and serves as the foundation for the development of the vertebral column. Non-chordates lack this structure entirely.

29. What is the post-anal tail in chordates, and why is it significant?

The post-anal tail is a muscular extension of the body that extends beyond the anus in chordates. It's significant because it's a unique feature of chordates, not found in non-chordates. This tail plays a crucial role in locomotion for many aquatic chordates and has been modified for various functions in terrestrial chordates, such as balance or communication.

30. How does segmentation differ between chordates and some non-chordates?

Both chordates and some non-chordates (like annelids and arthropods) exhibit segmentation, but the nature of this segmentation differs. In chordates, segmentation is primarily seen in the vertebral column, muscles, and nerves. In segmented non-chordates, the entire body is divided into similar repeating units. This difference reflects the distinct evolutionary paths and body plans of these groups.

31. What is the difference in skeletal structure between chordates and non-chordates?

Chordates typically have an endoskeleton, which is an internal skeleton made of cartilage or bone. This endoskeleton includes the vertebral column in most chordates. Non-chordates, on the other hand, may have no skeleton, an exoskeleton (external skeleton), or a hydrostatic skeleton. For example, arthropods have an exoskeleton made of chitin, while cnidarians rely on a hydrostatic skeleton.

32. How does the digestive system orientation differ between chordates and non-chordates?

In chordates, the digestive system runs ventrally (on the belly side) to the notochord or vertebral column. In many non-chordates, the orientation can vary. For instance, in echinoderms like sea stars, the digestive system is oriented radially. This difference in orientation is related to the overall body plan and evolutionary history of each group.

33. How does the presence of a notochord affect the body structure of chordates compared to non-chordates?

The notochord in chordates provides axial support and serves as a site of muscle attachment, allowing for more efficient locomotion, especially in aquatic environments. It also acts as a signaling center during development, influencing the formation of other structures. Non-chordates lack this central supporting and organizing structure, resulting in diverse body plans that use other means of support and organization.

34. How does the evolution of jaws differentiate some chordates from non-chordates?

The evolution of jaws is a key feature that separates gnathostomes (jawed vertebrates) from other animals. Jaws, derived from modified gill arches, allowed for more efficient feeding and eventually led to the development of teeth. Non-chordates and even some chordates (like lampreys) lack true jaws. Instead, they may have other feeding structures like radulas, proboscises, or filter-feeding mechanisms.

35. What is the difference in symmetry between chordates and non-chordates?

Chordates are bilaterally symmetrical throughout their lives, meaning their body can be divided into equal left and right halves. Non-chordates show more diversity in symmetry. While many are bilaterally symmetrical (like arthropods), others may have radial symmetry (like cnidarians) or even asymmetry (like some sponges). Some, like echinoderms, start life with bilateral symmetry but develop radial symmetry as adults.

36. How does the presence of an endoskeleton in chordates affect their growth compared to non-chordates?

The endoskeleton of chordates, particularly the bony skeleton of vertebrates, allows for continuous growth throughout life. Bones can grow and remodel in response to mechanical stresses. In contrast, many non-chordates with exoskeletons (like arthropods) must periodically shed their rigid outer covering to grow, a process called molting or ecdysis. This difference in growth patterns has significant implications for the life histories and ecological roles of these animals.

37. How does the presence of a closed circulatory system in chordates affect their physiology compared to non-chordates?

The closed circulatory system in chordates, where blood is contained within vessels, allows for more efficient transport of oxygen, nutrients, and waste products. This system, coupled with a heart that creates pressure, enables chordates to grow larger and be more active. Many non-chordates have open circulatory systems or no true circulatory system at all, which can limit their size and activity levels.

38. What is the difference in immune system complexity between chordates and non-chordates?

Chordates, particularly vertebrates, have a complex adaptive immune system with specialized cells (like T and B lymphocytes) and the ability to produce antibodies. This allows for a highly specific and memory-based response to pathogens. Non-chordates generally have innate immune systems, which are less specific but still effective. Some, like insects, have a form of adaptive immunity, but it's less complex than that of vertebrates.

39. How does the development of a head differ between chordates and non-chordates?

Chordates exhibit cephalization, the evolutionary trend towards a distinct head containing sensory organs and a brain. This is particularly pronounced in vertebrates. While many non-chordates also show cephalization (like arthropods), others (like echinoderms) may lack a distinct head region. The degree and nature of cephalization reflect the sensory and cognitive needs of different animal groups.

40. What is the difference in muscle arrangement between chordates and non-chordates?

Chordates typically have segmented muscles (myomeres) arranged along the body axis, often attached to the vertebral column or notochord. This arrangement allows for the undulating movements characteristic of many aquatic chordates. Non-chordates show a variety of muscle arrangements. For example, cnidarians have a simple net of muscle fibers, while mollusks often have a muscular foot for locomotion.

41. How does the presence of a coelom affect organ development in chordates compared to non-chordates?

The true coelom in chordates provides space for organ development and allows for the evolution of complex organ systems. It also enables more efficient circulation and creates a hydrostatic skeleton for some soft-bodied animals. In non-coelomate non-chordates (like flatworms), the lack of a body cavity constrains organ development and body size. Pseudocoelomate non-chordates (like nematodes) have some of the advantages of a body cavity but with limitations compared to true coelomates.

42. What is the difference in regeneration capabilities between chordates and non-chordates?

Many non-chordates have remarkable regeneration abilities. For example, planarians can regenerate an entire body from a small fragment, and starfish can regrow lost arms. While some chordates can regenerate certain body parts (like lizard t