Introduction

The animal kingdom is divided into two broad categories that are vertebrates and invertebrates. If you’ve ever wondered where we fall on the scale of vertebrates vs invertebrates, the answer is in your backbone. Vertebrates have a backbone, also known as a notochord, while invertebrates don’t. In this article, we are going to further differentiate these two categories of organisms Vertebrates Vs  Invertebrates in detail.

Vertebrates

Vertebrates are organisms that possess a vertebral column also known as notochord at any point in their lives. It means having a notochord at any point during an organism’s development is enough to classify it as a vertebrate.

The vertebral column is also known as the spinal column, which is composed of individual vertebrae. The vertebrae, which can be either made of bone or cartilage, are responsible for constructing the backbone or spinal column.

Characteristics of vertebrates

1. Presence of backbone or spinal column

This structure provides support and protection to the spinal cord, which is a part of the nervous system.

2. Bilateral symmetry

Vertebrates exhibit bilateral symmetry, which means that their bodies can be divided into two similar halves along a central axis.

3. Well-developed nervous system

Vertebrates typically have a centralized nervous system, which includes a brain and spinal cord. This intricate nervous system enables advanced sensory perception, motor coordination, and behavior.

4. Closed circulatory system

Vertebrates have a closed circulatory system, which includes a heart and blood vessels. Blood is circulated through the body in a closed loop, allowing for efficient oxygen and nutrient transport.

5. Respiration through specialized organs

Vertebrates have specialized respiratory organs such as lungs or gills, which allow for the exchange of gases, such as oxygen and carbon dioxide, with the environment.

6. Advanced sensory organs

Vertebrates often possess well-developed sensory organs, such as eyes, ears, noses, and touch receptors. This allows them to perceive their environment and respond to stimuli.

7. Reproductive diversity

Vertebrates exhibit diverse reproductive methods, including sexual reproduction with internal or external fertilisation, and a range of reproductive strategies such as oviparity (laying eggs) and viviparity (live birth).

8. Diverse body plans

Body plan refers to the overall structural organization and arrangement of body parts in animals, including features such as symmetry, segments, appendages, skeleton, body shape, and organ systems.

Vertebrates exhibit a wide range of body plans, including fish, amphibians, reptiles, birds, and mammals, with varied anatomical structures, physiological processes, and ecological roles.

These characteristics collectively make vertebrates a diverse and successful group of animals that occupy a wide range of habitats on Earth, including aquatic, terrestrial, and aerial environments (1).

Invertebrates

Invertebrates are organisms that do not have a backbone or spinal column in their body structure. They make up the majority of animal species on Earth and are incredibly diverse in terms of their anatomy, physiology, and ecological roles (2).

Characteristics of Invertebrates

They are cold-blooded animals meaning their body temperature is regulated by their external environment rather than by internal metabolic processes.

• They possess solid, external skeletons or hydrostatic skeletons.
• Most animals on the planet (95 percent of all animal species) are invertebrates.
• The majority of invertebrates, except insects, are aquatic animals.
• Invertebrates include animals from several phyla, such as Arthropoda (e.g., insects, spiders, crustaceans), Mollusca (e.g., snails, clams, squid), Porifera (sponges), Cnidaria (e.g., jellyfish, corals), Echinodermata (e.g., starfish, sea urchins), and many others. 

Vertebrates vs Invertebrates differences (3)

 Vertebrates vs Invertebrates similarities

 Q&A

1. Are Fishes invertebrates or vertebrates?

Fishes are vertebrates and are typically divided into three groups: superclass Agnatha (jawless fishes), class Chondrichthyes (cartilaginous fishes), and superclass Osteichthyes (bony fishes).

 2. Are Sharks vertebrates or invertebrates?

Sharks are vertebrates, belonging to the class Chondrichthyes, which includes cartilaginous fish and are characterized by having a skeleton made of cartilage rather than bone

3. Are Frogs vertebrates or invertebrates?

Frogs are vertebrates, belonging to the class Amphibia, which is a group of animals that includes frogs, toads, salamanders, and caecilians

4. How many vertebrate species are there?

 The exact number of vertebrate species is uncertain due to ongoing discoveries of new species. However, currently, there are estimated to be around 50,000 living species of vertebrates. Among them, fish make up the largest group with approximately 25,988 species, followed by mammals with 4,500 species, birds with 9,100 species, reptiles with 7,082 species, and amphibians with 4,880 species.

5. Are Insects vertebrates or invertebrates?

Insects are invertebrates, meaning they do not possess a backbone or spinal column. They belong to the phylum Arthropoda

6. Are Turtles vertebrates or invertebrates?

Turtles are vertebrates belonging to the class Reptilia. Turtles have a hard, protective shell made of bony plates that house their body and organs, and their backbone is part of their endoskeleton, which is a defining characteristic of vertebrates.

Written By: Deva Singh

Other References

• Rittner, D., & McCabe, T. L. (2004). Encyclopedia of Biology. Facts on File.
• Kotpal, R. L. (2010). Modern Text Book of Zoology: Vertebrates. Rastogi Publications.