Vertebrates vs Invertebrates: Understanding the Key Differences

If you were to start researching, you would be amazed at the varieties of creatures that exist on earth. Scientists have discovered 8.7 million types of creatures, but, even they, cannot say for sure that they have come across every living thing on earth. Seeing as the numbers are great, scientists came up with a system to help categorize and keep record of them.

In this post, we would talk about the two categories of animals; the difference between vertebrates and invertebrates to be specific.

We would explain what they are, their unique features, and how these two are different from the other.

Definition of Vertebrates

Vertebrates are animals characterized by well-advanced and defined internal skeletal system for different functions, including a structured backbone. To put it simply, they can be defined as animals with backbones and other numerous bones. The skeletal make-ups are made of bones and cartilages. These well-advanced skeletal structures help them to survive in just about any environment – water, air, and land.

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Aside from the skeleton, these animals also have cell walls and advanced nervous systems, features that are not available in the other case. They also have some special features like high organization, a well-developed brain bounded by a bone known as cranium, and an outer covering that consists of several protective skin layers.

Another outstanding quality that readily comes to view in any invertebrate vs vertebrate is their body symmetry. While the former has radial or bilateral symmetry, the latter has only bilateral symmetry. Also, their body structures differ in the sense that the former has a simple and unorganized nerve network, unlike the latter has complexed and highly specified organs with various functions.

Invertebrates are animals that are characterized basically by lack of backbones, proper skeletal or nervous systems. Unlike in the other case where the skeleton is internal, animals in this case have external skeleton, known as exoskeletons. This category of animals does not have developed bodies, are mostly small in size, and are mostly found in water bodies.

Scientists believe that the small size of these animals is a result of loosely organized nerve network and the lack of backbones, which means they do not have a support system. In comparison, they are generally slower because they do not have enough muscles to support their motion.

Interestingly, these backboneless animals make up about ninety-eight percent of the animal kingdom; an obvious fact that points out the difference between invertebrates and vertebrates. They have just one layer of skin, no cell walls, and are either heterotrophic or parasitic in nature.

Mode of Comparison Vertebrates Invertebrates

Definition Animals characterized by well-advanced and defined internal skeletal system for different functions, including a structured backbone Animals that are characterized basically by the lack of backbones, proper skeletal or nervous systems Body symmetry Bilateral symmetry Bilateral or radial symmetry Body structure Well-developed organs with designated functions. Mostly complex, with a well-organized nervous system Simple and unorganized nervous system Muscles Well-developed muscular system Less-developed muscles Skin layer Multiple skin layer Single skin layer Animal population Makes up 2% of the animal kingdom Makes up 98% of the animal kingdom Type of eye No compound eyes Compound eyes present Body size Mostly larger in comparison Mostly small in comparison Central nervous system A hollow tube at the mid-dorsal line A solid tube at the mid-ventral line Skeletal system Endo-skeletal system Exo-skeletal system Heart location Abdomen Dorsally Circulatory system Have a closed circulatory system Mostly have an open circulatory system Limbs May have one or two pairs of limbs May have more than two pairs of limbs Examples Mammals, amphibians, reptiles, birds, etc. Worms, jelly fishes, sponge, arthropod, start fish, etc.

Conclusion

In comparing the two major classifications of animals on earth – vertebrates vs invertebrates, we have shared with you the basic differences that can help you tell them apart. The presence of backbones and complex nervous systems in the former unlike in the latter, is the most notable difference. Another difference can be seen in the number of limbs they have. The former has not more than two pairs of limbs, but the latter may have more than that.