Vertebrates and Invertebrates are the two categories into which all the species of animals are classified. Animals are heterotrophic, multicellular organisms that are classified within the kingdom known as Animalia. The primary distinction between vertebrates and invertebrates lies in the fact that vertebrates comprise of a backbone while invertebrates don’t have an internal backbone. So, vertebrates have bilateral symmetry. Invertebrates display both radial and bilateral theorems. Vertebrates include amphibians, fish reptiles, birds and mammals. Invertebrates are jellyfish, sponges and worms as well as mollusks, arthropods, and even starfish. Vertebrates exhibit a greater organization in their body structure when as compared with invertebrates.

What are Vertebrates?

Vertebrates are mammals that have backbones. They belong to the phylum Chordata in the kingdom of Animalia. Vertebrates are the best-organized creatures on the planet. This group includes amphibians, fish, reptiles, birds, as well as mammals. The most distinctive feature of vertebrates are the presence a spinal cord, a notochord and vertebrae. It is nerve cord that is hollow located in the mid-dorsal region of the body in the embryonic phase. When adults reach adulthood, it’s substituted by the spine. The brain that is well developed is situated in the cranium.

Vertebrates are also equipped with pharyngeal-gill with slits that pair. The mouth and the esophagus cavity are linked to one through Gill slits. Certain fish have an endoskeleton with cartilaginous cartilage. All vertebrates have an endoskeleton made of bone. The vertebrates’ hearts is muscular and may be composed of three or even four chambers. Vertebrates have kidneys to facilitate elimination. They also have fins that are paired or legs.

What are Invertebrates?

Invertebrates are animals without backbones. Invertebrates are among the largest creatures on the planet and live in all habitats. Invertebrates include jellyfish, sponges and worms, as well as molluscs, arthropods and starfish. Invertebrates do not also develop a notochord. Invertebrates’ blood temperatures is similar to that of the external environment. Invertebrates are cold-blooded creatures. Because of the absence of an endoskeleton that is strong invertebrates are tinier and slow.

The majority of invertebrates are comprised of an elongated body that includes an thorax, head, and abdomen. The respiratory process is carried out through the skin of most invertebrates. Some are able to develop Gills. Some invertebrates develop a chitinous exoskeleton. The majority of invertebrates are hermaphrodites. 

Similarities Between Vertebrates and Invertebrates

• Vertebrates and Invertebrates are part of the kingdom of Animalia.
• Both vertebrates, as well as invertebrates, exhibit bilateral invertebrates and vertebrates show bilateral.
• Gills are common in vertebrates as well as invertebrates.
• Both vertebrates as well as invertebrates share the same nervous system.
• Both vertebrates as well as invertebrates have hearts.

Difference Between Vertebrates and Invertebrates

1. Differences in Physical Characteristics

Invertebrates don’t have backbones and vertebrates have a robust internal skeleton that is composed comprising bone and cartilage as well as an extremely developed brain which is enclosed by the skull. The nerve cord is surrounded by vertebrae, the individual bones that form vertebrate’s spinal. Vertebrates are well-developed in their sensory organs, respiratory systems that includes lungs or gills and a bilateral symmetry that is accompanied by their advanced nervous system which differentiates them from vertebrates.

Vertebrates can be classified into two categories that includes animals with jaws (Agnatha) and animals that have jaws (Gnathostomata). Although most vertebrates are mobile as well as are heterotrophic (i.e. they are unable to make themselves food) however, some vertebrates might be able to create the food they consume.

Due to the lack of a support system the majority of invertebrates are tiny. Invertebrates possess two fundamental body plans. One is the radial-symmetry plan (a circular shape with an elongated central mouth like how spokes extend out from the center of the wheel) that is a group of animals that spend their entire lives to one spot and bilateral symmetry plans (right half and left mirroring each the other, and usually have an identifiable front and back). This is the case for animals that are constantly looking for food.

2. Differences in Habitat

Both kinds of animals reside in diverse habitats, but vertebrates basically adapt to every habitat. The well-developed neuromuscular system, as well as internal skeletons that vertebrates have allow the animals to adjust to the land or sea as well as air.

Invertebrates are found in a variety of habitats, ranging from deserts and forests, in caves as well as seabed and mud.

3. Population of Vertebrates vs. Invertebrates

At present, more than 2 million invertebrates are discovered. The 2 million species approximately 98% of the animals that have been identified across the animal kingdom i.e. the 98th percentile of 100 species of animals currently are invertebrates. However vertebrates comprise only 2percent of all animals. Human beings are vertebrates.

4. Differences in Classification

Vertebrates are classified as reptiles, amphibians, fish birds, mammals, and amphibians. In contrast, invertebrates comprise sponges coelenterates (Ctenophora or comb jellies and Cnidaria (also known as coral creatures, genuine jellies sea anemones and sea pens as well as their hybrids) Echinoderms (starfish sea urchins sea cucumbers) as well as Mollusks, worms (squid Octopus, snails bivalves) as well as arthropods (insects).

5. Differences in Size

One of the major distinctions between vertebrates and invertebrates is the dimensions. Invertebrates like shellfish, worms or insects, tend to be tiny and slow-moving due to the lack of efficient ways of supporting an enormous body as well as the muscles required to support it. However, there are some exceptions, such as the squid, that can be as large as fifteen metres (50 feet) in size. Vertebrates have a flexible support system. Therefore, vertebrates can build larger and more powerful structures than other vertebrates.

6. Adaptation to the Environment

Contrary to invertebrates vertebrates possess a well-developed nervous system. Thanks to their special nerve-fiber system they are able to respond quickly to changes in their environment which gives them a advantage in competition. Comparatively with vertebrates (animals with backbones) Invertebrates are characterized by basic nervous systems and they operate almost on instinct. This system is effective all the time, even though they are usually incapable of making mistakes and learning from them. Moths for instance often flutter about with bright lights, and they do so at the risk of being burned. The only exceptions to this are octopuses and their closest relatives, who are believed to be one of the most intelligent species within the invertebrate kingdom.

Evolution of Invertebrates

Invertebrates are multicellular organisms. They represent a number of steps on the path to the complexity of organization that make the majority of species what they are now. The first form of life was as tiny cells that were found in water. Invertebrates were the first species of multicellular creatures that developed in the water. Invertebrates set the stage for the evolution of other organisms when simple transformations started to occur (see the microevolution). These changes were simple and created complex creatures that were vertebrates.

Comparison chart – Differences between Invertebrates and Vertebrates – Invertebrates vs Vertebrates

Characteristics	Invertebrates (Non-Chordates)	Vertebrates (Chordates)
Symmetry	Radial, Bi-radial or Absent	Bilateral
Metamerism	Metamerism that is true or pseudo-realistic or Absent	Metamerism that is true
Post-anal tail	Absent	Usually Present
The quality of the organization	Organ-system or Protoplasmic	Organ System
Germ Layers	Two (diploblastic), Three (Triploblastic) or Absent	Three (Triploblastic)
Coelom	Acoelomate, pseudocoelomate , or Truly coelomate	Truly coelomate
Limbs derivation	The same segments	From several segments
Notochord	Notochord or Backbone Absent	In some form or substituted by a backbone composed of the ring-like vertebrae
Position of the Gut	Dorsal part of the nerve cord	Nerve cord to Ventral
Pharyngeal Gill-slits	Absent	At some point in life
Anus	Starts on the final segment, or in the absence of	It is differentiated and opens prior to the final segment
Blood vascular system	Open, Closed or Absent	Closed and well developed
Heart	Dorsal, Lateral or Absent	Ventrally located
Blood vessel in the Dorsal	The blood flows to the front	The blood flows to the posterior
Hepatic portal system	Absent	Present
Hemoglobin	Plasma or absent	The red corpuscles of blood contain
Respiration	Through the body’s through the body’s surface, gills, or through the tracheae	Through gills and lungs
Nervous System	Solid	Hollow
Brain	Above the pharynx, or Absent	Dorsal to pharynx of the head
Nerve cord	Ventral, Double, generally bearing the ganglia	Dorsal, single, and without Ganglia
Segmental nerve roots	Ventral and Dorsal roots do not distinct	Ventral and dorsal roots are distinct.
Reproduction	Asexual reproduction predominant	Sexual reproduction predominant
Regeneration power	Usually, it is good	Most of the time, it is poor
Temperature of the body	Cold-blooded	Warm-blooded or cold