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

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.

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:

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, or 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.

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.

Chordates and Non-Chordates Reproductive Strategies

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: Fertilisation is found in both the external and internal types among chordates. Internal fertilisation is typical for the majority of the terrestrial and some of the aquatic animals; reproductive organs are involved here.

• Non-chordates: Many non-chordates employ external fertilisation, whereby the eggs and sperm are released to the surroundings and fertilised. 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. The 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.

Some Chordates v/s Non Chordates NEET MCQs

Question: Characteristics of non-chordates is/are

1. Absence of notochord

2. Absence of post and tail

3. Hemoglobin, if present is dissolved in plasma

4. All of these

Correct Answer: 4) All of these

Explanation: Non-chordates share several important traits. The notochord, a rod-like structure present in chordates like fish and humans, is the first thing they lack. Second, a characteristic of chordates that non-chordates lack is a post-anal tail. Finally, whereas haemoglobin is transported within red blood cells in chordates, it is dissolved in the blood plasma of non-chordates. Non-chordates frequently have these characteristics: no post-anal tail, no notochord, and dissolved haemoglobin.

Hence, the correct answer is option 4)All of these.

Question: Which is true for Non-Chordates?

1. Ventral Nerve Cord

2. Post-anal tail

3. Pharynx

4. Vertebral Column

Correct Answer: 1) Ventral Nerve Cord

Explanation: Non-chordates are animals that lack a notochord or backbone and exhibit distinct structural differences from chordates. They do not have a post-anal tail, and their circulatory system varies—many lack a heart, while in others, the heart is positioned dorsally or laterally. Their nerve cord is solid and ventral, unlike chordates, which have a hollow, dorsal nerve cord. Non-chordates include diverse groups such as arthropods, molluscs, annelids, and echinoderms, each with unique adaptations suited to their environments.

Hence, the correct answer is option 1) Ventral Nerve Cord

Question: In some chordates, the notochord is modified as the vertebral column, and such animals are called vertebrates. Which of the following makes sense?

1. All chordates are vertebrates, but not all vertebrates are chordates

2. All vertebrates are chordates, and all chordates are vertebrates

3. All vertebrates are chordates, but not all chordates are vertebrates

4. Chordates are not vertebrates, and vertebrates are not chordates

Correct Answer: 3) All vertebrates are chordates, but not all chordates are vertebrates.

Explanation: All organisms belonging to the Phylum Chordata are characterised by the presence of a notochord at least during some stage of their life cycle. In vertebrates, this notochord appears during the embryonic stage and is later replaced by the vertebral column, which is a defining feature of vertebrates.

Every vertebrate has a notochord at some point in its life, making it a chordate.

Not all chordates, such as tunicates and lancelets, grow a backbone; they are not all vertebrates. Among chordates with a spine, vertebrates constitute a unique group.

Hence, the correct answer is option 3) All vertebrates are chordates, but not all chordates are vertebrates.