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10.2: Vertebrate Characteristics

Difficulty Level: At Grade Created by: CK-12
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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).

Comparison of the size of a whale, carp, and human

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 seven classes (Table below).

Class Common Name Characteristics Examples
Agnatha Jawless fishes No jaws or scales. Lampreys, hagfish
Chondrichthyes Cartilaginous fishes Skeletons consisting of hard, rubber-like cartilage. Sharks, rays
Osteichthyes Bony fishes Skeletons made of bone. Tuna, bass, salmon, trout
Amphibia Amphibians Spend part of their lives under water and part on land Frogs, toads, salamanders
Reptilia Reptiles Have lungs to breathe on land, skin that does not need to be kept wet, and produces a watertight (amniotic) egg. Turtles, snakes, lizards, alligators
Aves Birds Produces watertight eggs and protects eggs from predators. Ostriches, penguins, flamingos, parrots
Mammalia Mammals Nourish young with milk through mammary glands. Dogs, cats, bears, monkeys, humans


Explore More

Use the resources below to answer the questions that follow.

Explore More I

  1. What do scientists feel was a key factor in vertebrates getting "big"?
  2. What advantages do big animals have over small animals?
  3. What advantages do small animals have over big animals?
  4. What did jaws allow vertebrates to do?
  5. What is a "larvacean"? How does it feed?

Explore More II

  1. What is a phylogeny?
  2. When did the evolution of archosaurs begin?
  3. What are the living members of archosaurs?


  1. What are five examples of vertebrates?
  2. What are the primary feature shared by vertebrates? What is the role of this feature?
  3. What is the defining characteristic of the cartilaginous fish?
  4. What are the defining characteristics of reptiles?
  5. What is the defining characteristic of mammals?

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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.

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Difficulty Level:
At Grade
7 , 8
Date Created:
Nov 29, 2012
Last Modified:
Aug 30, 2016
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