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10.2: Vertebrate Characteristics

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What animals have a backbone?

You have a backbone, or vertebrate (or vertebral) column. Can you guess what other animals also have a backbone? Frogs, snakes, birds, and many other animals all have backbones. Animals that have backbones are known as vertebrates.

Introduction to Vertebrates

Vertebrates are animals with backbones. These include fish, amphibians, reptiles, birds, and mammals.

Characteristics of Vertebrates

The primary feature shared by all vertebrates is the vertebral column , or backbone. The vertebral column protects the spinal cord.

Other typical vertebrate traits include:

  • The cranium (skull) to protect the brain. The brain is attached to the spinal cord.
  • An internal skeleton. The internal skeleton supports the animal, protects internal organs, and allows for movement.
  • A defined head region with a brain. The head region has an accumulation of sense organs.

Living vertebrates range in size from a carp species, as little as 0.3 inches, to the blue whale, which can be as large as 110 feet ( Figure below ).

A species of carp and an image of the blue whale (a mammal), the largest living vertebrate, reaching up to 110 feet long. Shown below it is the smallest whale species, Hector's dolphin (about 5 feet in length), and beside it is a human. These images are not to scale. The carp is greatly exaggerated in size and is even smaller than depicted when compared to the blue whale.

Classification of Vertebrates

Vertebrates, or subphylum Vertebrata, are all members of the phylum Chordata. Although there is some disagreement on how to classify animals, the traditional system divides the vertebrates into six classes ( Table below ).

Class Common name Characteristics Examples
Class Agnatha jawless fishes no jaws or scales lampreys and hagfish
Class Chondrichthyes cartilaginous fishes skeletons consisting of hard rubber-like cartilage sharks and rays
Class Osteichthyes bony fishes skeletons made of bone tuna, bass, salmon, and trout
Class Amphibia amphibians spend part of their lives under water and part on land frogs, toads, and salamanders
Class Reptilia reptiles have lungs to breathe on land and skin that does not need to be kept wet, and produces a water-tight ( amniotic ) egg turtles, snakes, lizards, and alligators
Class Aves birds produces water-tight eggs and protects eggs from predators ostriches, penguins, flamingos, and parrots
Class Mammalia mammals nourish young with milk through mammary glands dogs, cats, bears, monkeys, and humans


  • amniotic egg : A shelled egg that can be laid on land; prevents embryo from drying-out.
  • cranium : Protective brain case; also called the skull.
  • mammary gland : Milk-producing gland of female mammals.
  • vertebral column : Bony support structure that runs along the back of a vertebrate animal; also called the backbone.
  • vertebrate : Animal with backbone; these include mammals, birds, reptiles, amphibians, and fish.


  • Vertebrates are animals with a backbone.
  • Vertebrates include the mammals, birds, reptiles, amphibians, and fish.


Use the resources below to answer the questions that follow.

  1. What do scientists feel was a key factor in vertebrates getting "big"?
  2. What advantages do big animals have over small animals? Be as complete as you can in your answer.
  3. What advantages do small animals have over big animals? Be as complete as you can in your answer.
  4. What did jaws allow vertebrates to do?
  5. What is a "larvacean"? How does it feed?
  1. What is unique to vertebrates?
  2. What characteristics define Archosaurs? Who belongs to this group? Who are its living members?
  3. What characteristics define Amniotes? Why is this characteristic useful to life on land?


  1. What are some examples of vertebrates?
  2. What are the main features shared by the vertebrates?

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Difficulty Level:

At Grade


7 , 8

Date Created:

Nov 29, 2012

Last Modified:

Oct 08, 2014
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