Invertebrate vs. Vertebrate

What's the Difference?

Invertebrates and vertebrates are two major categories of animals that differ in their physical characteristics and evolutionary traits. Invertebrates, which make up about 95% of all animal species, lack a backbone or vertebral column. They include a wide range of organisms such as insects, worms, mollusks, and jellyfish. In contrast, vertebrates are animals with a well-developed internal skeleton made up of bones or cartilage. This group includes mammals, birds, reptiles, amphibians, and fish. Vertebrates generally have more complex body structures and organ systems compared to invertebrates. Additionally, vertebrates often possess a highly developed nervous system, allowing for more advanced behaviors and cognitive abilities.


Photo by USGS on Unsplash
Skeletal SystemExoskeleton or hydrostatic skeletonEndoskeleton
Body SymmetryRadial or bilateral symmetryBilateral symmetry
Nervous SystemSimple or complex nerve netCentralized nervous system
RespirationVaries (gills, tracheae, diffusion)Lungs or gills
Circulatory SystemOpen or closed circulatory systemClosed circulatory system
ReproductionSexual or asexual reproductionSexual reproduction
Number of SpeciesOver 95% of animal speciesLess than 5% of animal species
Photo by Chris Curry on Unsplash

Further Detail


When it comes to the animal kingdom, there are two major groups that encompass a vast array of species: invertebrates and vertebrates. Invertebrates are animals that lack a backbone or vertebral column, while vertebrates are animals that possess a well-developed internal skeleton made of bone or cartilage. These two groups differ in various attributes, including their body structure, reproduction, habitat, and evolutionary history. In this article, we will explore the characteristics of invertebrates and vertebrates, highlighting their similarities and differences.

Body Structure

In terms of body structure, invertebrates exhibit a wide range of forms and sizes. They can be as small as microscopic organisms or as large as giant squids. Invertebrates include animals such as insects, spiders, worms, mollusks, and crustaceans. On the other hand, vertebrates have a more standardized body plan. They typically have a head, trunk, and tail, with bilateral symmetry. Vertebrates include animals like fish, amphibians, reptiles, birds, and mammals.

One of the key distinctions between invertebrates and vertebrates lies in their skeletal systems. Invertebrates lack a backbone, which means they rely on other structures for support and protection. Some invertebrates, like insects, have an exoskeleton made of chitin, while others, like worms, have a hydrostatic skeleton. In contrast, vertebrates possess an internal skeleton composed of bone or cartilage, providing them with a more rigid framework.


Reproduction strategies also differ between invertebrates and vertebrates. Invertebrates employ a wide range of reproductive methods, including sexual and asexual reproduction. Many invertebrates, such as insects and mollusks, reproduce sexually, with males and females engaging in mating behaviors. However, some invertebrates, like certain species of worms and jellyfish, can reproduce asexually through processes like budding or fragmentation.

On the other hand, vertebrates primarily reproduce sexually. They have well-developed reproductive systems, with distinct male and female individuals. Vertebrates typically engage in courtship rituals and copulation, leading to the fertilization of eggs. Some vertebrates, like birds and mammals, exhibit complex behaviors and parental care to ensure the survival of their offspring.


In terms of habitat, invertebrates are incredibly diverse and can be found in almost every environment on Earth. They inhabit terrestrial, freshwater, and marine ecosystems. Insects, for example, are highly adaptable and can be found in forests, deserts, and even urban areas. Invertebrates also play crucial roles in various ecological niches, such as pollination, decomposition, and nutrient cycling.

Vertebrates, on the other hand, have a more limited distribution. While some vertebrates, like birds and mammals, have successfully colonized diverse habitats, many vertebrates are restricted to specific environments. Fish, for instance, are primarily aquatic and inhabit freshwater and marine ecosystems. Reptiles are often found in warm climates, while amphibians are closely associated with moist environments.

Evolutionary History

When it comes to evolutionary history, invertebrates have a much longer lineage compared to vertebrates. In fact, the majority of animal species are invertebrates. They have been present on Earth for millions of years and have undergone significant diversification. Invertebrates played a crucial role in shaping ecosystems and paved the way for the emergence of vertebrates.

Vertebrates, on the other hand, evolved from a group of invertebrates known as chordates. The first vertebrates appeared around 500 million years ago, during the Cambrian period. They were jawless fish and gradually gave rise to more complex forms, including the first jawed fish, amphibians, reptiles, birds, and mammals. Vertebrates have since become the dominant group of animals on land and in the oceans.


In conclusion, invertebrates and vertebrates represent two distinct groups within the animal kingdom. Invertebrates, lacking a backbone, exhibit a wide range of body structures and have diverse reproductive strategies. They can be found in various habitats and have a long evolutionary history. On the other hand, vertebrates possess an internal skeleton, reproduce primarily sexually, have more limited habitat distributions, and have evolved from a group of invertebrates. Understanding the attributes of these two groups helps us appreciate the incredible diversity and complexity of the animal world.

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