What Are Vertebrates?

By | September 9, 2016

A donkey, a crocodile, a fish, a parrot, and a frog all have one thing in common. They all have a backbone, or vertebral column, connected to a supporting bony skeleton inside their bodies. They are all vertebrates.

FA/MILY TREE OF VERTEBRATES

Although vertebrates are the animals we know most about, they actually make up just a tiny part of the animal kingdom. Vertebrates with limbs—tetrapods—are all descended from fish. Vertebrates can be divided into five groups: mammals, birds, reptiles, amphibians, and fish.

MAMMALS

chimpanzee

Chimpanzee


Mammals can be divided into three groups, depending on their means of reproduction. Placental mammals give birth to well-developed young. Marsupials give birth to undeveloped young. Monotremes (there are just five living species) lay eggs.

GERBIL

gebril

Rodents are a large group of mammals, characterized by large incisors, perfect for gnawing.

AFRICAN ELEPHANT

african-elephant

The largest living land mammal in the world, a male African elephant can stand 13 ft (4 m) at the shoulder.

BIRDS

budgerigar

Budgerigar


There are almost 10,000 species of bird. They are the living descendants of dinosaurs, but they developed the ability to fly. Feathers help them to fly, but also keep them warm.

COMMON RHEA

common-rhea

Not all birds can fly. In fact, more than 40 species of bird, like this rhea, have lost the ability to fly.

PEREGRINE FALCON

peregrine-falcon

This is one of the fastest of all animals.

REPTILES

parson-chameleon

Parson’s chameleon


Along with some amphibians, reptiles were the first vertebrates to live entirely on land. Their skin is dry and covered in scales to help retain water, a necessary adaptation, since many reptiles live in warm areas with limited access to water.

MILK SNAKE

milk-snake

Some species of reptile have to shed their skin as they grow. They do this between four and eight times a year.

CAIMAN

caiman

Crocodilians, such as the caiman, have thrived since they appeared with early dinosaurs, some 200 million years ago.

AMPHIBIANS

chinese-giant-salamander

Chinese giant salamander (the world’s largest living amphibian).


Modern amphibians have moist, soft skin, and most amphibians can absorb oxygen through this skin in addition to having lungs. They largely live on land but require damp conditions. Most have to return to water to lay eggs.

FIRE SALAMANDER

fire-salamander

This salamander will curl up underground in colder, winter months. Its bright color warns predators it is poisonous.

POISON DART FROG

poison-dart-frog

There are some 4,500 species of frog and toad, including about 120 species of poison dart frog.

FISH

spinny-puffer-fish

Spinny puffer fish


Earth’s first vertebrates—fish— now form more than half of all vertebrate species. Gills allow them to breathe underwater.

WHALE SHARK

whale-shark

This is the world’s largest fish. Despite its size, it feeds on plankton—tiny organisms that drift in water.

STAYING TOGETHER

fish-school

Many fish swim in schools, finding safety in numbers.

TAKE A LOOK—A PEEP INSIDE

maiasaura-skeleton

Skeleton of Maiasaura, a duck-billed dinosaur

Vertebrates have a backbone and internal bony skeleton. They also have a highly developed nervous system, and a larger brain for body size than invertebrates. Blood is pumped around the body by the heart, supplying the vertebrate’s body with food and oxygen and removing waste products. They breathe using lungs.

BONE is a lightweight, living organ, and it is found only in vertebrates. Because it is supplied with blood vessels, it can grow (unlike the hard casing of an invertebrate such as a crab, which has to be shed to allow growth).

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