Difference Between Vertebrates and Invertebrates

Edited by Diffzy | Updated on: May 28, 2023


Difference Between Vertebrates and Invertebrates

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Animals inhabit every corner of the world. They are so diverse that you can find anywhere from the top of the mountains to the depth of the oceans. All the animals are widely distributed in a classification hierarchy based on their shape and size.

Though, in this article, we are going to distinguish animals by their backbones. And those animals which have a backbone are known as vertebrates. Another class of animals, that do not have a backbone are known as invertebrates. Continue with this article to deeply get an insight into this classification of animals based on their backbone.

Vertebrates vs Invertebrates

Vertebrates are typically more complex as compared to invertebrates, with a more developed nervous system and a greater level of cognitive function. They have an integral skeleton made up of bones and cartilage that provide support and protection for their internal organs. They also have a wide range of reproductive strategies, including internal and external fertilization. Coming to invertebrates, on the other hand, there is a lack of a true skeleton and instead, have an exoskeleton or a hydrostatic skeleton. They are generally less complex than vertebrates, having a simpler nervous system.  They are also found in a variety of habitats, but many are restricted to specific environments.

Difference between Vertebrates and Invertebrates in tabular form

DefinitionAnimals with internal skeletons are made up of bones.Animals without a backbone.
SizeCan range from tiny fish to massive elephants and whales.Can range from tiny insects to giant squid.
SkeletonThey are made up of bones and cartilage, which came to be known as endoskeletons.They are made up of chitin and other materials, which came to be known as endoskeletons.
Nervous systemCentral nervous system with a brain and spinal cord.Have a decentralized nervous system or ganglia.
Reproduction Most sexually reproducing with internal fertilization.Can reproduce sexually or asexually with external fertilization.
RespirationHave lungs, gills, or skin for respiration. Have a variety of respiratory structures such as spiracles or gills.
Digestive system Have a complete and complex digestive system with a mouth, stomach etc.Have an incomplete digestive system with a single opening.
MovementMay have limbs, wings, or fins for movement.May have legs tentacles or other structures for movement
Complexity Tend to be more complex in terms of behaviour, anatomy and physiology.Tend to be less complex in terms of behaviour, anatomy, and physiology.
PredationCan be both Predators and prey in various ecosystems.It can be both but often preyed upon by vertebrates.
Location of heartThe heart is in the abdomen.The heart is located dorsally.
Circulatory systemHave an open circulatory system.Mostly have a closed circulatory system.
Existence5% of animal species are vertebrates.95% of animal species are invertebrates.


Vertebrata is a subphylum of the Chordata phylum. They are mostly categorized as Vertebrates as they have backbones and vertebrae. They have a muscular system made up of a bilaterally paired aggregated and partially encased central nervous system. If we consider the literal term, then they must have a vertebral column. The initial vertebrates did not have one, instead, they possessed a notochord. The vertebrate is known to be a distinct head, a differentiated brain, and pairs of sense organs. The body’s tail and trunk portions are separated. The presence of pharyngeal openings with gills indicates a high metabolic rate.

A tabular spinal cord encloses a developed notochord. It consists of a muscle mass that is segmented and that flanks. A sensory ganglion arises on the dorsal root, of the spinal nerve and segmental autonomic form below notochord. The trunk region is filled with a vast, bilateral body cavity known as a coelom. The digestive system consists of an oesophagus that connects the stomach and a gut that connects the stomach to the anus.

Unlike, invertebrates, vertebrates possess the quality of having a spinal cord. The derivation of the term vertebrates takes the bones that create the spine. The body of a vertebrate is generally divided into several parts; a brief description of the same is given below:

  • Gill Arches: In some amphibians, as well as fish, have the purpose of supporting the gills. Some of the arches are found to be evolved in the form of other organs, jaws for instance.
  • Bones: These a helpful for the joints, these are a series of stiff and short vertebrae. It is protective towards the spinal cord. The joints existing between the vertebrae allow the backbone to bend.
  • Braincase: It is also called the cranium, which is responsible for protecting the brain.

The vertebrates are generally found to have pairs of sense organs including otic, optic, and nasal; a differentiated tabular brain along with a separate head. Generally, their body is divided into tail and trunk regions and the presence of gills with pharyngeal slits signifies that their metabolic rate is relatively high.

Fish are the most diverse group of vertebrates, and are found in a wide range of aquatic environments. Amphibians can live both on land and in water including frogs, toads, and salamanders. Reptiles on the other hand are typically terrestrial and include snakes, lizards, turtles, and crocodiles. Birds are characterized by their feathers and ability to fly, while mammary glands that produce milk for their young ones as well as other features such as hair or fur and a four-chambered heart.

Some additional facts that should be known about vertebrates are:

  • The first vertebrates appeared in the form of fish which is jawless around 500 million years ago. Over time, vertebrates evolved by several key features, such as jaws, paired fins or limbs and the ability to breathe air.
  • These are majorly divided into groups: fish and tetrapods. Fish are broadly divided into two sub-classes: jawless (hagfish and lampreys) and on the other hand jawed fish (sharks, rays). Tetrapods are mostly four-limbed vertebrates and include amphibians, reptiles, birds, and mammals.
  • Vertebrates have a closed circulatory system, which means that blood is confined to vessels and flows throughout the body in a controlled manner. This mostly allows for the efficient transport of oxygen and nutrients to tissues and organs.
  • The evolution of jaws was a breakthrough in vertebrate history, as it allowed for more efficient feeding and predation. The first most jawed fish appeared around 420 million years ago.

The evolution period of amniotic eggs in reptiles helped them to reproduce on land and led to the development of reptiles, birds and mammals. These eggs have a protective membrane that prevents desiccation and also provides nutrients for the developing embryo inside it.

  • Birds are thought to have an evolution from very small, feathered theropod dinosaurs which are around 150 million years back. They have several adaptions for fighting, including lightweight bones, powerful chest muscles, and feathers.

Overall, vertebrates are a remarkable group of animals that have evolved a wide range of adaptations that also allowed them to survive and thrive in diverse environments, their diversity and contribution to the ecosystem and human society make them a fascinating subject of study for scientists and nature enthusiasts alike.


An animal that does not possess or develop the vertebral column that is usually grown from the notochord is usually termed an invertebrate. They are animals without a skeletal system, as a result, many of them lack an intricate body type structure and cannot develop to enormous sizes. The open circulatory system of the invertebrates helps to flow the blood via an open cavity. The respiratory system of the invertebrates is simple with the gills and trachea being the most common. Theirs an external skeleton to protect their soft, inner body. This material is frequently made from chitin, a glucose derivative. These usually are little and do not grow to be especially large. They do not possess lungs as they are adapted to breathe through their skin. Gamete fission commonly occurs during reproduction.

Except for the subphylum Vertebrata, this class includes all the animals. It does not possess a backbone and can exist anywhere on the Earth's surface. In the canopies of the wettest rainforests, high reaches of the atmosphere, and the driest of desserts; These groups of animals are found. Many invertebrates have developed unique adaptation skills that enable them to survive and thrive in their environments. Some of them are:

  • Arthropods are the largest group of invertebrates and include a wide range of insects, spiders, crustaceans, and centipedes. They have jointed legs, a hard exoskeleton, and a segmented body.
  • Molluscs are another major group of invertebrates, including snails, clams, and squids. They have a soft, unsegmented body and also have a protective shell. Some molluscs, like octopuses and squids, are highly intelligent and have a complex nervous system. They are essential for marine and freshwater ecosystems as filter feeders and scavengers.
  • Echinoderms are a group of invertebrates consisting of starfish, sea, urchins, and sea cucumbers. They have a spiny exoskeleton and also have a spiny exoskeleton. Echinoderms are a member of the marine ecosystem, playing roles in predation and herbivory.
  • Cnidarians are a group of invertebrates which includes jellyfish, corals, and sea anemones. They also have radial symmetry and tentacles with stinging cells called nematocysts. Cnidarians are also essential for marine ecosystems and play a vital role as predators and prey.

Invertebrates constitute more than 97 per cent of all species in the animal kingdom. The number of invertebrates exceeds 2 million species, with more found almost every other day. They also provide essential services towards humans, such as food, medicine, and ecosystem services. Overall invertebrates are fascinating creatures that continue to intrigue and inspire scientists for research.

Difference between Invertebrates and Vertebrates in points

  • Vertebrates are animals, that have spinal cords. And due to the presence of that spinal cord inside their bodies helps them to communicate or form a connection between the brain and the rest of the body. Whereas, Invertebrates are those animals which lack a centralized spinal cord, but they create a connection between the brain and body through a decentralized spinal cord or ganglia (clusters of nerve cells) and the presence of some nerve cords.
  • If you go into the deep analysis of the nervous system between the two types of animals, you would understand that both vertebrates and invertebrates have nervous systems, but their structure inside is different. Vertebrates have a nervous system, which is highly organised and is divided into multiple regions to perform various functions. Whereas, in the case of 'invertebrates' they too have a nervous system, but the structure ranges widely from single nerve cells to complex formation of nerve cells. For example, Cnidarians have simple nerve nets, and arthropods and cephalopods have complex nervous systems.
  • Vertebrates have internal skeletal structures made from components like bones and cartilage. The internal one provides better protection to the internal organs when you compare it with the external one. It also provides mobility and flexibility over external skeletal structures. Whereas, invertebrates have external ones, which help them take different shapes. Vertebrates benefit more than invertebrates.


Vertebrates and invertebrates are the two major classifications of animals that have a backbone, while the others one does not. The vertebrates depend on the invertebrates, the plants and one another. Many vertebrates rely on invertebrates as a primary source of food. Coming to invertebrates, play an important role in maintaining soil health, they break down organic matter and help to aerate the soil. The balance of vertebrates and invertebrates in the ecosystem plays a huge role in the food web, without invertebrates the food web would have been disrupted leading to potential cascading effects on vertebrates. In the process of habitat making vertebrates such as birds use invertebrates while nest-making. The relationship between vertebrates and invertebrates is complex yet interconnected, with each group playing an essential role in maintaining a healthy ecosystem. Overall, both groups of animals continue to provide insights into the complexity and diversity of life on Earth.


  • https://en.wikipedia.org/wiki/Invertebrate
  • Differences Between Invertebrates And Vertebrates (byjus.com)
  • Vertebrate - Wikipedia


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"Difference Between Vertebrates and Invertebrates." Diffzy.com, 2024. Thu. 29 Feb. 2024. <https://www.diffzy.com/article/difference-between-vertebrates-and-invertebrates>.

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