The Different Classes of Animals

The animal kingdom is comprised of six classes: mammals, birds, reptiles, amphibians, fish and invertebrates. All animals are classified into one of these categories. Beyond that they are sorted into order, family, genus and species.

Mammals and birds

Mammals and birds are both warm-blooded vertebrates that breathe air. Mammals give birth to live young and feed them through a female's ability to produce milk ("mamma" literally meaning "breast" in Latin). Birds, however, lay eggs and have wings and feathers. Some common mammals are humans, cats, dogs and cattle. A few examples of birds are finches, parrots and penguins.

Reptiles and amphibians

Reptiles and amphibians are cold-blooded vertebrates that breathe air. Reptiles mostly lay eggs, with the exception of some snakes and are carnivorous. Amphibians also lay eggs, although they are soft-shelled, and go through multiple stages of development before reaching adulthood. Snakes, turtles and crocodiles are reptiles while frogs and salamanders are amphibians.

Fish and invertebrates

Fish are generally cold-blooded vertebrate animals that breathe water instead of air. They lay eggs that are fertilized outside of the female's body and have fins instead of limbs. Invertebrates do not have spines, unlike the other five animal classes, and lay fertilized eggs. Some examples of fish are trout, tuna and goldfish. Examples of invertebrates include flies, spiders and worms.

You can classify any and all living, breathing animals into one of the above classes. If you are unsure of what class an animal belongs to, check your local library or search the internet. There are also wildlife posters that identify the different classes of animals.