Guide to Scientific Classification of Animals

Scientific Classification

There are over 1.5 million different types of living organisms on planet Earth, ranging from microorganisms and simple bacteria that are invisible to the naked eye to large, complex mammals and sea creatures.

From the beginning of time, as humans began to study and understand the natural earth, they have found suitable names for these living organisms and categorized them into various groups based on their differences and similarities.

So what are animals? If you suddenly come across a creature you’ve never seen or heard of before, how would you know if it’s an animal or something else?

Well, somehow, we all know the answer to this question, whether we know how to put it in words or not. Let us attempt to answer this question.

Basic characteristics of Animals

  • Feed on organic material (plants or the flesh of other animals)
  • Move around to find food
  • Take their food into their bodies and digest it afterward.
  • Most species reproduce by having eggs fertilized by sperm

Some people may be tempted to add that animals have fur, run around on all fours and give birth to offsprings that they feed on milk.

While these people may sound correct, they are wrong, as this explanation reflects only mammals. This means you have temporarily forgotten that frogs, birds, snakes, crocodiles, and even fish are also animals.

These creatures are all members of the group known as the vertebrates (or simply described as animals with a backbone).

Mammals make up only about 8% of this group, with fish taking up 55%, primitive vertebrates taking up 4%, birds 16%, reptiles 12%, and amphibians 5%.

However, it is vital to note that the term animal does not only include vertebrates.

In fact, a vertebrate is a group that makes up only a very tiny portion of all animals, 90% of the creatures in the animal kingdom are invertebrates, and these invertebrates include worms and insects (now you know why insects may take over the world soon)

Classification of vertebrates

Vertebrate animals are divided into five groups or classes, namely:

  • Amphibian (frogs and toads)
  • Fish
  • Birds
  • Reptiles (snakes and crocodiles)
  • Mammals

These classifications are all based on apparent similarities. For example, all mammals have similar skeletal structures, have hair or fur on their bodies, are warm-blooded, and suckle their young.

Even though the animals in the class “Mammalia” (the mammals) have several similarities, they still have some differences.

There are three subclasses within the class:

  • Marsupials (animals like the kangaroo with pouches)
  • Duck-billed platypus and the spiny anteater
  • True mammals (with a placenta)

Within the subclass that contains the true mammals, you can also find groupings known as orders that have mammals that are more closely alike or related, than others.

Below are examples of six mammalian orders:

  • Rodents (Rodentia) (rats and mice)
  • Carnivores (Carnivora) (dogs, cats, bears, and seals)
  • Even-toed grazers (Artiodactyla) ( sheep, pigs, cattle, antelopes)
  • Odd-toed grazers (Perissodactyla) (donkeys, horses, zebras)
  • Primates (monkeys, apes, humans)
  • Marine mammals (Cetacea) (whales, sea cows)

Within every order, there are a variety of families. For instance, within the carnivorous mammals are the following families:

  • Felidae (cat-like carnivores)
  • Canidae (dog-like carnivores)

Even at that, it is very possible to find some groupings that are closely related more than others. These groups that are more closely related are called genera (singular genus).

For example, within the cat family known as Felidae is a genus called Felis containing cats, as well as genera containing lynxes, panthers, and saber-toothed tigers!

The final groups within the animal classification system are the species. You must have heard the word species.

The definition of species is a collection of animals that can successfully mate and produce fertile offspring.

This means that all domestic cats are members of the species Felis domesticus; this is because all breeds of cat, whether Manx, Siamese, or ordinary Household cats can crossbreed.

However, domestic cats can’t mate successfully with tigers, lions, or jaguars, so these kinds of cats are placed in different species, e.g., Felis Tigris, Felis Leo, and Felis onca.0

Within the same species also, there can be some animals with broad variations in appearance that can still successfully breed. We call these different breeds, varieties, or races.

For example, there are many different dog breeds from Chihuahua to the Dalmatian breed of cats, from Manx to Siamese and domestic short-hair cats, but all can be crossbred. Often, these breeds have been created by selective breeding.

Still, it is possible for varieties to arise in the wild when different groups of animals are separated by a sea or mountain range and have developed a wide range of characteristics over long periods.

In summary, the Animal Kingdom is divided into:

  • Phyla are divided into classes
  • Classes are divided into orders
  • Orders are divided into families
  • Families are divided into genera
  • Genera are divided into species
  • Species have no other division.


Every living organism on the planet are first categorized into different kingdoms. Life on earth is categorized into five different kingdoms, which are Animal kingdom, Plant kingdom, Bacteria, Fungi, and Protists (single-celled organisms).


The animal kingdom is shared into 40 smaller groups or categories, known as a phylum. In these categories, animals are grouped according to their main features.

The animals in this category usually fall under one of the five different phyla, which are Chordata (vertebrates), Cnidaria (invertebrates),  Molluscs, Arthropods, and Echinoderms.


The group called phylum is then shared into even smaller groups, called classes. The Chordata (vertebrates) phylum is split into Actinopterygii (Bony Fish), Mammalia (Mammals), Chondrichthyes (Cartilaginous Fish), Amphibia (Amphibians), Aves (Birds), and Reptilia (Reptiles).


Each of the classes is divided into smaller groups again, called orders. For instance, the class of animals, which is known as Mammalia (Mammals), is split into various groups, including Primate, Carnivora, Rodentia, and Artiodactyla.


In every order, there are various families of animals that all possess very similar traits or features. The Carnivora order, for instance, breaks into families that include Canidae (Dogs), Felidae (Cats), Ursidae (bears), and Mustelidae (Weasels).


Every category of animal family is further divided into small groups called genus. Each of the genera has animals that possess very similar features and are also closely related.

The Felidae (Cat) family, for instance, contains a genus that includes Felis (small Cats and domestic Cats), Puma (Panthers and Cougars), and Panthera (Tigers, Leopards, Jaguars, and Lions).


Each animal species within a genus is named after it’s specific characteristics and features. The names of almost every animal are in Latin so that they can easily be understood all. Over the world, and they all consist of two words.

The first word in the name of any animal is usually the genus, with the other name indicating the specific species.

Example – Orang-utan

  • Kingdom: Animalia (Animal)
  • Phylum: Chordata (Vertebrate)
  • Class: Mammalia (Mammal)
  • Order: Primates
  • Family: Hominidae (Great Apes)
  • Genus: Pongo
  • Species: Pongo pygmaeus (Orang-Utan)

Now that you are familiar with animal classification, you may want to memorize them by learning the acronyms K.P.C.O.F.G.S and letting each letter represent an exciting word that you will always remember.

Let us know what your questions or opinions are by leaving a comment below.

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