What are Vertebrates?

What are Vertebrates?

The Vertebrates are the subphylum of chordates that possess a backbone or spinal column and comprise all fish, amphibians, reptiles, birds, and mammals. We name them vertebrates because they all have spinal columns or vertebrae.

An Introduction to Vertebrates

We can divide animals on Earth into five major groups depending on their body structure. These groups, known as taxonomic classes, include Aves (birds), Amphibia (amphibians), Reptilia (reptiles and snakes), Osteichthyes (fishes), and Mammalia (mammals). Animals that belong to these classes are vertebrates. Animals with a backbone—because they have a special spinal column made of more than 25 vertebrae. The types of vertebrate animals you’ll find on Earth today range from fish that live in icy waters at extreme ocean depths to birds that can fly at altitudes higher than commercial airplanes.

Define vertebrates

A vertebrate is an animal that has a spinal column. These animals have a backbone. This separates them from invertebrates. Examples of vertebrates include amphibians, reptiles, birds, mammals, and fish. These animals also all have internal skeletons, as opposed to having exoskeletons like invertebrates do. Not all types of animals are vertebrates. Some animals fall into other categories, such as invertebrates, and there are many names for categories within those larger groups as well.


It comes from two Latin words, vertebra (or vértebræ) and animus (ánimas), meaning literally joint soul. However, it has come to refer not only to those with a backbone but also to more complex organisms than just fish and amphibians. Those organisms which have an internal skeleton composed of bones rather than cartilage or other soft tissues are called vertebrates.

Respiratory system

Fish, amphibians, reptiles, and birds all have a respiratory system that consists of internal gills or lungs. These are lined with tiny, thin-walled blood vessels known as capillaries. When a fish or bird breathes air into its lungs, oxygen passes through these capillaries to enter its bloodstream; carbon dioxide then passes from its bloodstream into these same vessels and is carried back to be exhaled out of its mouth or nose. Amphibians’ skin also has numerous pores used for breathing.

Digestive system

The digestive system is responsible for taking in food, breaking it down, and using those nutrients to fuel our cells. The vertebrate digestive system consists of a mouth, esophagus, stomach, intestines, and anus (yes, these animals have an anus). And we’re not just talking about humans here: Most mammals—including humans—and some reptiles have a basic digestive system. Birds don’t have an anus (they poop out of their butt) but they also don’t really chew their food because they swallow most of it whole. Fish and amphibians lack teeth and a large intestine but they do still digest food in some way. You might be thinking that there’s no clear pattern to all these random bits of information, but there is.

The Spinal Cord

An essential part of a vertebrate’s nervous system, it’s in charge of receiving sensory input from other parts of the body and then transmitting that information to various regions of your brain. Basically, it’s in charge of relaying messages from your environment to your brain so you can respond accordingly. It is kind of like an automated messaging system within your body; if you touch something hot, for example, it’ll quickly relay that message to your brain so you can pull away. Without one, you wouldn’t be able to move any part of your body on your own – though some animals (like starfish) can survive without them because they have an alternate brain called a ganglion instead.

Brain Development invertebrates

All vertebrate species share a few things in common. They all: have a backbone, have specialized nerve cells called neurons, and develop complex brains. It’s brain development that separates vertebrates from other life forms. As embryonic neural stem cells divide and become increasingly specialized (differentiated), they develop into different cell types of nerve tissue which creates a collection of cells that work together as an organ to control how we think, move, feel, breathe and perform other basic bodily functions. This is why we humans share so many similar features with other vertebrate species even though they look very different from us!

Excretory system

All animals with a backbone must remove waste from their body. The way that they do it, however, is extremely diverse. For example, flatworms have nephridia—tube-like organs that allow for waste excretion and filtration through blood vessels. Unlike mammals that have kidneys to perform these processes, planarians rely on nephridia as their main method of waste removal. They also filter blood using fine membranes between layers of cells rather than complete organ systems like humans do with our kidneys and livers (Rutherford). All animals without a backbone, such as invertebrates, have distinct ways of getting rid of their bodily wastes; you can find out more by visiting AQUA’s webpage on vertebrate excretory systems here.

Evolutionary history of vertebrates

The first vertebrate was a fish, specifically one of our jawless fish ancestors from about 500 million years ago. These ancient forms have cartilaginous skeletons, meaning that their skeleton is flexible, non-calcified cartilage (unlike today’s fish and amphibians). As you can imagine, without bone or bony structures to support them, these creatures were light and had to rely on muscles to give them structure. This feature became one of their greatest strengths as it allowed them to develop fast-moving bodies that could dart in and out of coral reefs with ease. The downside is that they didn’t have a solid skeletal system so they couldn’t grow very large before they broke apart.

Classification of vertebrates

There are about 65,000 species of vertebrates, including fish. Most vertebrates belong to one of two broad groups: amphibians (including frogs and salamanders) or reptiles (including turtles, snakes, lizards, and their extinct relatives). A third less familiar group is mammals—warm-blooded animals that nourish their young with milk from mammary glands. Mammals differ from other vertebrates in having a backbone composed of four chondrocrania made of cartilage instead of three.

Classification of Vertebrates illustration

Allergies and Disease Resistance invertebrates

Allergies have no effect on vertebrates because they have developed a protective shield of mucus and antibodies that protect them from foreign particles. Diseases can affect humans, but these vertebrates are able to develop a greater resistance than other animals. For example, more dogs die from skin conditions than heart attacks. Animals with a backbone also require more nutrients, so their immune system is much stronger than non-vertebrate animals. Therefore, some non-bone marrow animals catch very few diseases as opposed to humans and other vertebrate species. Examples include salamanders, who rarely get sick compared to humans because of their strong immune systems.

How They Reproduce

Most vertebrates reproduce by sexual reproduction, which involves two types of cells: gametes and embryos. Gametes are eggs and sperm, or their equivalents. Gametes contain half a cell’s DNA; to create an embryo, two gametes must combine. A key difference between invertebrate animals and vertebrate animals is that in most cases, invertebrate embryos develop within a gummy liquid inside their mother’s body (an egg). While some fish lay eggs that hatch outside of their bodies and a few amphibians lay live offspring directly on land, for mammals and birds—and all other vertebrates—eggs must be incubated internally.


Vertebrate animals have an internal skeleton that supports their body. Examples of vertebrates include fish, reptiles, amphibians, birds, and mammals. Although these animals come in a variety of shapes and sizes they all have four things in common: they have backbones; they develop from eggs; they breathe air (oxygen), and most are warm-blooded.

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