Animal Classification

Animal Classification: How Scientists Make Sense Of The Animal Kingdom By Naming And Grouping Species.

Animal classification facts and information for kids and students: how we make sense of the animal kingdom by naming and grouping species. Discover the 8 levels of animal classification.

A free printable worksheet is available for this page. Click here or on the image below to download. Answers can be found on our worksheets page.

Animal Classification Worksheet

Free printable animal classification worksheet. Click image to download.

On this page we’re going to discover how classification helps us to understand how all species are related, and how they evolved.

You can read the whole page to become an expert at animal classification (recommended!), or use the links below to jump straight to the facts you need.

Find out more about the animal kingdom at our main animals page.

What Is Animal Classification?

  • Animal classification is the process of identifying, naming and organizing animal species into groups.
  • The branch of science that deals with animal classification is known as ‘taxonomy’.

You’ve probably heard of animal groups such as ‘mammals’ and ‘insects’. They are just two of the many groups that are used to categorize animals. Animals in groups such as these have certain things in common; they are ‘related’ to each other in some way.

Mammal Insect Comparison

Think of a typical mammal and a typical insect. Picture them both in your head. What are the main differences between them? No matter which animals you chose, they are clearly very different to one another.

Sometimes the differences between groups of animals aren’t quite so obvious. Crocodiles and alligators, for example, look similar, yet are in different families.

Crocodile

Crocodiles, such as this Nile crocodile, are in a different family than alligators.

(A family is one type of animal group, you’ll meet others further down the page!)

Sometimes similarities between species are even more misleading. Think of a dolphin and a shark. Both live in the sea, both eat fish, and both look broadly similar. Yet the dolphin is a mammal, and the shark is a fish.

Bottlenose Dolphin

Shark

All of the shark’s ancestors lived in the sea. The dolphin’s ancestors left the sea, evolved into mammals, then returned to the sea. (How amazing is that?)

If we hadn’t studied and classified mammals and fish we would never have known this.

Animal Classification Is Continuously Changing

African Elephant

African bush elephant: one of the THREE elephant species alive today.

Animal classification now uses sophisticated scientific methods to identify relationships between species.

Because the methods used to classify animals are continuously changing, the groups in which species are placed are sometimes changed. Occasionally, new species are identified!

For example, for many years elephants were classified into 2 species: African elephants and Asian elephants.

In 2010, DNA tests on African elephants revealed that there are actually 2 species of African elephant: African bush elephants and African forest elephants.

This means that there are now 3 species of elephant in total!

Why Do We Classify Animals?

Finding out how different species are related to each other helps us to make sense of the animal kingdom. It also helps us to understand how animals evolved.

Animal classification is like putting together a huge ‘family tree’ containing every species – even those which are now extinct, such as dinosaurs.

The Different Levels of Animal Classification

animalia kingdom

The animal kingdom is a big group that contains every animal (including humans). The scientific name for the animal kingdom is Animalia.

Characteristics of animals include being able to move, and needing to consume other organisms (or the products of other organisms) for nourishment.

Species that don’t share these characteristics, such as plants and fungi, don’t belong in Animalia; they have their own kingdoms!

fly agaric mushroom

The fly agaric mushroom (Amanita muscaria) – a fungus – belongs in the kingdom Fungi.

sequoia tree

Sequoia trees are in the kingdom Plantae.

Classification doesn’t actually begin with kingdoms. As we’ll find out below, classification begins with groups called domains.

Taxonomic Ranks

Taxonomic Ranks

Taxonomic Ranks. As species are classified into smaller and smaller groups the members of those groups become ever-more closely related.

In classification, each large group of species can be divided into smaller groups. The species in each of the smaller groups are more like each other – more closely related to each other – than they are to the animals in the bigger group.

For example, the class Mammalia (mammals) is divided into several smaller groups, including the orders Carnivora (mammals who have the same, meat-eating, ancestors) and Artiodactyla (herbivorous mammals such as pigs, deer, hippos and cattle).

Polar Bear

Polar bears are mammals, and members of Carnivora.

Hippopotamus

Hippos are mammals, and members of Artiodactyla.

It doesn’t stop there. The species in a group such as Carnivora can be divided into even smaller groups. Smaller groups within Carnivora include the cat family (Felidae) and the dog family (Canidae).

Male Lion

Lions are members of the order Carnivora and the family Felidae.

Coyote

Coyotes are members of the order Carnivora and the family Canidae.

The members of the cat family are more closely related to each other than they are to members of the dog family.

You can continue through the layers of classification by dividing the groups into smaller and smaller groups, each containing ever-more closely related animals, until you’re left with the individual species themselves.

The layers of different groups are known as taxonomic ranks. There are 8 main taxonomic ranks, from domain down to species. They are: domain, kingdom, phylum, class, order, family, genus, and species.

Taxonomic Rank Mnemonic

You can use the mnemonic* ‘daring king Phillip came over for good spaghetti’ to remember the taxonomic ranks (or perhaps you can think of your own phrase).

*A mnemonic is a way of remembering something.

  • Daring (Domain)
  • King (Kingdom)
  • Phillip (Phylum)
  • Came (Class)
  • Over (Order)
  • For (Family)
  • Good (Genus)
  • Spaghetti (Species)

The 8 Levels of Animal Classification: How the Gray Wolf is Classified

Gray Wolf Classification

Discover how to classify a gray wolf (Canis lupus).

We’re now going to take a closer look at each of the taxonomic ranks. We’ll use the gray wolf (Canis lupus) as an example. (UK spelling: grey wolf).

Domain

Classification Domain Eukarya

Gray wolf, common sunflower and fly agaric mushroom. The grey wolf is in the domain Eukarya along with plants and fungi.

The first groups that living things are divided into are domains. There are only three domains: Eukarya, Bacteria and Archaea. Together they contain every single living thing.

Archaea and bacteria are groups of single-celled microorganisms. Although they resemble one another, there are several biochemical differences between archaea and bacteria.

Eukarya is the domain that contains fungi, plants, animals and protists. In fact, any organism whose cells have a nucleus is a Eukaryote.

The three domains were identified by microbiologist Carl Woese.

  • The gray wolf is a Eukaryote.

Kingdom

Classification Kingdom Animalia

Gray wolf, bald eagle and common octopus. The grey wolf is in the kingdom Animalia along with all other animals, including birds and molluscs

Domains are a relatively recent taxonomic rank. Before the technology that enabled us to identify the different domains existed, the highest taxonomic rank was kingdom.

Eukaryotes such as the gray wolf (an animal), sunflower (a plant) and fly agaric mushroom (a fungus) are clearly very different to each other. They are separated into different kingdoms.

There are either 5 or 6 kingdoms depending on where you go to school!

In the USA, the kingdoms are: Animalia (the animal kingdom), Plantae (the plant kingdom), Fungi, Protista, Archaea and Bacteria.

In other parts of the world, the kingdoms are: Animalia, Plantae, Fungi, Protista and Monera (which includes Archaea and Bacteria).

Common Sunflower (Helianthus annuus)

The common sunflower (Helianthus annuus) belongs in the kingdom Plantae (the plant kingdom).

As we’ve already found, every animal is a member of Animalia, the animal kingdom.

  • The gray wolf is a member of Animalia.

Phylum

Animal Classification Phylum

Gray wolf, bald eagle and common frog. The grey wolf is in the phylum Chordata, and the subphylum Vertebrata, along with all animals with backbones, such as birds and amphibians.

Loosely speaking, members of the same phylum have the same overall body plan. For example, members of the animal phylum Chordata (chordates) all have a notochord – a flexible central rod.

There are actually additional ranks between the main taxonomic ranks. Under phylum is a rank called subphylum.

Vertebrata

The subphylum Vertebrata is the group of animals that have backbones. Members of this group are known as vertebrates. (‘Invertebrates’ is a term used to describe all animals outside of this group.)

Red Eyed Tree Frog

Red eyed tree frogs have backbones, and are therefore in the subphylum Chordata.

  • The gray wolf is in the phylum Chordata, and the subphylum Vertebrata.

Class

Animal Classification Class

Gray wolf, eastern gorilla and bottlenose dolphin. All belong in the class Mammalia.

As we work our way down through the ranks, the animals in each group become more and more alike. The animals in a class such as Mammalia (mammals) all share certain characteristics. For example, all mammals have hair and are warm blooded (yes, even whales and dolphins have hair, although it’s sometimes only present on very young animals).

Other examples of animal classes include: Arachnida (spiders & scorpions, etc.), Insecta (insects), Aves (birds) and Reptilia (snakes and lizards, etc.)

  • The gray wolf is a mammal (i.e. a member of the class Mammalia).

Order

Animal Classification Order

Gray wolf, tiger and walrus: all are members of  the order Carnivora.

The animals in a class are split into smaller groups called orders. For example the class Mammalia (mammals) contains orders such as: Proboscidea (elephants), Sirenia (dugongs, manatees, and sea cows), Primates (apes and monkeys) and Rodentia (mice, rats and beavers, etc.)

  • The gray wolf is in the order Carnivora. The members of this order are called carnivorans. Dogs, cats, bears and pinnipeds (seals, sea lions and walruses) are members of this order. They are all descended from the same meat-eating ancestors.

Family

Animal Classification Family

Gray wolf, fennec fox and red fox. All are in the family Canidae, which includes dogs, foxes and jackals.

Animal families are groups of related animals. The species in a family share many of the same characteristics. They are often similar in overall appearance.

Examples of animal families include Hominidae (great ape family), Corvidae (crow family) and Delphinidae (oceanic dolphin family).

Man

Humans are members of the Hominidae family.

  • The gray wolf is a member of the Canidae (dog) family.

Genus

Animal Classification Genus

The grey wolf is in the genus Canis with coyotes and jackals

Animals of the same genus are closely related to each other. They are usually similar in appearance and behavior.

When talking about more than one genus, use the plural, genera.

Examples of genera include: Felis (‘small’ cats such as the wildcat Felis silvestris and domestic cat Felis catus), Haliaeetus (sea eagles such as the bald eagle Haliaeetus leucocephalus and white-tailed eagle Haliaeetus albicilla).

The genus to which an organism belongs makes up the first part of its scientific name. For example, the wildcat’s scientific name is Felis silvestris, therefore it is a member of the genus Felis.

  • The gray wolf Canis lupus is a member of the genus Canis. This genus also includes wolves, jackals and coyotes.

Species

Animal Classification Species

There are around 37 subspecies of grey wolf. They include the dingo and (believe it or not) the domestic dog.

Members of the same species are able to reproduce and create fertile offspring.

Species can be further split into subspecies. Although subspecies are essentially the same type of animal, there may be slight differences between them, and they usually live in different areas. Subspecies of the same species are able to breed and create fertile offspring.

  • The gray wolf has a large number of subspecies, which include the Eurasian wolf, Arctic wolf, Northwestern wolf, dingo and domestic dog.
  • For many years, the domestic dog has been selectively bred by man. As a result of this, it differs considerably in size and appearance. Most animal subspecies look more alike!

Animal Classification Examples Chart

The table below shows how various well-known animals are classified.

English NameGray wolfGreat White SharkOstrichNile crocodileRed Eyed Tree FrogCommon OctopusMan
Gray Wolf ClassificationGreat White Shark ClassificationOstrich ClassificationNile Crocodile ClassificationRed Eyed Tree Frog ClassificationCommon OctopusMan
DomainEukaryaEukaryaEukaryaEukaryaEukaryaEukaryaEukarya
KingdomAnimaliaAnimaliaAnimaliaAnimaliaAnimaliaAnimaliaAnimalia
PhylumChordataChordataChordataChordataChordataMollusca Chordata
ClassMammalia (mammals)Chondrichthyes (cartilaginous fish)Aves (birds)Reptilia (reptiles)Amphibia (amphibians)Cephalopoda (cephalopods)Mammalia (mammals)
OrderCarnivora Lamniformes StruthioniformesCrocodiliaAnuraOctopodaPrimates
FamilyCanidaeLamnidaeStruthionidaeCrocodylidaeHylidaeOctopodidaeHominidae
GenusCanisCarcharodon StruthioCrocodylusAgalychnisOctopusHomo
SpeciesCanis lupusCarcharodon carchariasStruthio camelusCrocodylus niloticusAgalychnis callidryasOctopus vulgarisHomo sapiens

The History of Animal Classification

Throughout history man has observed, named and compared animals and plants. The Ancient Greek philosopher Aristotle classified species according to various characteristics, including whether they gave birth or laid eggs, or if they were warm or cold-blooded.

The Roman naturalist Pliny the Elder wrote Naturalis Historia, a large work in which many plants were described. (It is also considered to be the first encyclopedia.)

Over the years, animal classification became more scientific. 16th century Italian philosopher Andrea Cesalpino classified plants according to their fruits and seeds.

English naturalist John Ray published works on botany and zoology in the 17th century. He classified species according to the similarities that he observed, and was the first person to offer a scientific definition of the word species.

Swedish botanist Carl Linnaeus (1707-1778) is known as the ‘father of modern taxonomy’. He popularized the binomial naming system, and introduced the use of kingdoms, classes, orders, genera and species. The Linnaean system is still in use today.

Animal Classification for Kids & Students: Conclusion

We hope that you have enjoyed this explanation of animal classification, and that you now know a little more about how the various groups of animals are related to each other.

Essentially, animal classification is about evolution. Finding out how animals are related to each other helps us to work out how species evolved.

It’s like creating a huge family tree that stretches back over millions and millions of years, right back to when life on Earth was nothing more than a few single-celled organisms floating in the sea.

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