Types of Animals

Mammals, reptiles, and birds are the three main members of the animal kingdom. 

They have certain common characteristics:

  • They are all vertebrates (have a backbone).
  • They all have an internal skeleton to provide support and structure.
  • Mammals and birds are warm-blooded, while reptiles are cold-blooded.
  • Mammals and birds live on all continents of the world. Reptiles live on all continents except Antarctica.

There are some differences as well between mammals, reptiles, and birds.

Let’s dive in and learn about these three groups of animals!


Mammals live primarily on land, while some live in water. They have some unique characteristics:

  • Mammals have more complex brains and are the most intelligent living beings.
  • They are usually born alive and grow inside their mother’s body before birth.
  • Mammals feed their young ones with milk from the mammary glands. 
  • Most mammals grow hair or fur during their lifetime.


Reptiles include crocodiles, snakes, lizards, turtles, and tortoises. They have some unique characteristics:

  • Reptiles have a special skin made of scales or bony plates. 
  • Some reptiles shed their skin in a process called molting.
  • Reptiles are cold-blooded and cannot regulate their body temperature. They move into the sun or shade as required.
  • Most reptiles lay eggs to reproduce.


Birds are animals that have adapted for flight. They can also run, swim, dive, and jump. They have some unique characteristics:

  • Birds have wings instead of forelimbs to help them fly.
  • Feathers cover the body of birds.
  • Birds have a specialized digestive system that helps them eat when flying and digest the food later.
  • Birds lay eggs to reproduce.

Fun Facts

Here are some fascinating facts about mammals, reptiles, and birds!!

  • Bats are the only mammals that can fly.
  • Duck-billed platypus and four species of Echidna are the only mammals that lay eggs to reproduce.
  • Boas and pythons are the only reptiles that give birth to live young ones.
  • Not all birds can fly! Some birds, such as the ostrich, kiwi, penguin, and cassowary, are flightless.


Let’s quickly recap what we learned about mammals, reptiles, and birds.

  • What are the two common physical structures among mammals, reptiles, and birds? Backbone and Internal Skeleton
  • How do cold-blooded reptiles regulate their body temperature? By moving into the sun or shade
  • How do mammals reproduce? Give birth to live young ones
  • How do reptiles and birds reproduce? Lay eggs
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