Difference Between Vertebrates vs Invertebrates

Have you ever wondered how many living creatures there are on earth? The truth is, scientists strongly believe they have not encountered every single one of them, even though they have about 8.7 million of them on record. Because the numbers are so great, scientists came up with a system to help categorize and keep track of these creatures.

There are two main groupings we would like to discuss in this post. On a more specific note, we will take a look at the difference between vertebrates and invertebrates.

Definition of Vertebrates

Vertebrates are defined as animals with verified biological advancement characterized by endoskeletons that make up the back bones and perform other functions as well. To put it simply, they can be defined as creatures with backbones and other numerous bones.

The skeletal system is made of bones and cartilage. These well-advanced bone structures help them to survive in just about any environment – water, air, or land.

Aside from the skeleton, these creatures also have cell walls, advanced nervous systems, high organization ability, and a skull bone known as a cranium that houses a well-developed brain. Every creature in this category has several protective skin layers as well.

A feature that is particularly of interest in the invertebrate vs vertebrate comparison 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, which has complex and highly specified organs with various functions.

Definition of Invertebrates

Invertebrates are animals that are characterized by a lack of backbone. They have no proper nervous or bone structures. Unlike in the other case where the skeleton is internal, members in this case have external skeletons known as exoskeletons. This category does not have developed bodies, are mostly small in size, and are mostly found in water bodies.

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

Interestingly, they do make up about ninety-eight percent of animals, 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.

Main Differences Between Vertebrates vs Invertebrates

Here is a tabular representation of some of the differences between these major categories summarizing in simpler terms, the most common features that show how they vary from one another.

Basis of Comparison	Vertebrates	Invertebrates
Definition	Animals characterized by well-advanced and defined internal bones for different functions, including a structured backbone	Animals that are characterized basically by the lack of backbones, proper nervous systems and skeleton
Body symmetry	Bilateral symmetry	Bilateral or radial symmetry
Body structure	Well-developed organs with designated functions. complex for the most part, with a well-organized nervous system	Simple and unorganized nervous system
Muscles	Well-developed muscular system	Less-developed muscles
Skin layer	Multiple skin layers	Single skin layer
Population	Makes up 2% in total	Makes up 98% in total
Type of eye	No compound eyes	Compound eyes present
Body size	Mostly larger in comparison	Mostly small in comparison
Central nervous system	A tube at the mid-dorsal line	A hard tube at the mid-ventral line
Skeletal system	Structured beneath the outer layer	Structured as the outermost layer
Heart location	Abdomen	Dorsally
Circulatory system	Have a closed circulatory system	Mostly have an open circulatory system
Limbs	A pair at least	Two pairs in the very least
Examples	Mammals, amphibians, birds, reptiles, etc.	Worms, jelly fishes, sponge, arthropod, start fish, etc.

Difference Between Vertebrates and Invertebrates: Conclusion

In comparing these two major orderings – vertebrates vs invertebrates, we have shared with you the 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 no more than two pairs of limbs, but the latter may have more than that.