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Did you know that there are over 1.5 million different species of animals on this planet? That's a lot of creatures!

It can be difficult to keep track of them all, especially when they all fall into different classification categories. In this article, we will discuss the different ways animals can be classified, as well as provide a comprehensive guide to scientific classification for animals.

What is Scientific Classification?

Scientific classification (or taxonomy) is the process of grouping animals into different categories. These categories are based on similarities or shared characteristics, such as diet ( carnivore, herbivore etc.), habitat, anatomy, or behavior. Scientists use animal classification to help them study and understand the natural world.

This system of classification was developed by Swedish botanist Carl Linnaeus during the 1700s. The Linnaeus Method, also known as Linnaean Taxonomy, creates a hierarchy of groupings called taxa, as well as binomial nomenclature that gives each animal species a two-word scientific name. The first word in the name is the genus, which is a general grouping of animals with similar characteristics. The second word is the specific name, which is used to identify a particular species within the genus.

The method of giving scientific names to animals is typically rooted in Latin by combining the genus and species. For example, caribou are classified as Rangifer tarandus while polar bears are Ursus maritimus.

The Linnaean system of animal classification has changed and evolved as our understanding of the natural world has grown. In the early 1800s, French biologist Georges Cuvier developed the concept of extinction, which led to a major revision of Linnaean taxonomy. In the 1900s, German zoologist Ernst Mayr defined species as groups of animals that can interbreed and produce viable offspring. This definition is still used today.

The more features that a group of animals shares, the more specific that animal classification group is. Every species is defined based on nine branching categories.

The method of scientific classification is:

The Six Kingdoms

When Linnaeus developed his system of classification, there were only two kingdoms, Plants and Animals. But the invention of the microscope led to the discovery of new organisms and the identification of differences in animal and plant cells. A two-kingdom system was no longer useful.

Today the system of classification includes six kingdoms.

How are organism placed into their kingdoms?

1. Cell type, complex or simple

2. Their ability to make food

3. The number of cells in their body

Plants

You are probably quite familiar with the members of this kingdom as it contains all the plants that you have come to know - flowering plants, mosses, and ferns. Plants are all multicellular and consist of complex cells.

In addition, plants are autotrophs, organisms that make their own food.

With over 250,000 species, the plant kingdom is the second largest kingdom.

Plant species range from the tiny green mosses to giant trees.

Without plants, life on Earth would not exist!

Plants feed almost all the heterotrophs (organisms that eat other organisms) on Earth.

Animals

The animal kingdom is the largest kingdom with over 1 million known species. All animals consist of many complex cells. They are also heterotrophs. Members of the animal kingdom are found in the most diverse environments in the world.

Archaebacteria

In 1983, scientists tool samples from a spot deep in the Pacific Ocean where hot gases and molten rock boiled into the ocean form the Earth's interior. To their surprise they discovered unicellular (one cell) organisms in the samples. These organisms are today classified in the kingdom, Archaebacteria.

Archaebacteria are found in extreme environments such as hot boiling water and thermal vents under conditions with no oxygen or highly acid environments. The hot springs of Yellowstone National Park, USA, were among the first places Archaebacteria were discovered.

Eubacteria

Like archaebacteria, eubacteria are complex and single celled. Most bacteria are in the EUBACTERIA kingdom. They are the kinds found everywhere and are the ones people are most familiar with. Eubacteria are classified in their own kingdom because their chemical makeup is different. Most eubacteria are helpful. Some produce vitamins and foods like yogurt. However, some eubacteria such as Streptococci can give you strep throat!

Fungi

Mushrooms, mold and mildew are all examples of organisms in the kingdom fungi. Most fungi are multicellular and consists of many complex cells. Fungi are organisms that biologists once confused with plants, however, unlike plants, fungi cannot make their own food. Most obtain their food from parts of plants that are decaying in the soil.

Protists

Slime molds and algae are protists. Sometimes they are called the odds and ends kingdom because its members are so different from one another. Protists include all microscopic organisms that are not bacteria, not animals, not plants and not fungi. Most protists are unicellular. You may be wondering why those protists are not classified in the Archaebacteria or Eubacteria kingdoms. It is because, unlike bacteria, protists are complex cells.

Animal Phylums Explained

The most common way to classify animals is by their phyla, or major body plan. There are 35+ animal phylums or phyla. Here is a shortlist of the most common ones:

Porifera - multi-celled simple sea creatures i.e. sponges

Cnidaria - primarily marine animals including the corals, hydras, jellyfish, sea anemones, sea pens etc.

Platyhelminthes - a group of soft-bodied, usually much flattened invertebrates i.e. flatworms

Annelida - segmented worms; characterized by the possession of a body cavity, movable bristles, and a body divided into segments e.g. earthworms

Mollusca - molluscs e.g. Sea slugs, squids, snails, and scallops

Arthropoda - invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Most insects and arachnids e.g. tarantula

Chordata - vertebrates such as mammals, fish, reptiles and birds. e.g. puffins

Animal Classes

There are seven main classes of animals:

Agnatha (jawless fish) - group of primitive jawless fishes that includes the lamprey

Chrondrichtyes (cartilaginous fish) - a major class of jawed fish whose skeleton is characterized by rubbery cartilage e.g. sharks

Osteichthyes (bony fish) - diverse taxonomic group of fish that have skeletons primarily composed of bone tissue

Amphibia (amphibians) - small vertebrates that need water, or a moist environment, to survive.

Reptilia (reptiles) - Cold-blooded vertebrates, lay eggs

Aves (birds) - Warm-blooded vertebrates, lay eggs, feathers

Mammalia (mammals) - Warm-blooded, give birth to live young, nurse their young with milk

Animal Orders

Now that we know the animal classes, let's move on to animal orders. This is where things start to get a little more specific. For example, all lizards are reptiles, but not all reptiles are lizards.

There are around 35 orders of mammals and over 50 orders of reptiles. here are a few examples of each.
Mammals: Reptiles:
Animal Families

Now we're getting even more specific. Animal families are groups of closely related animals within an order. For example, the Felidae family includes all cats, from lions to house cats.

There are over 100 mammal families and over 200 reptile families. Here are a few examples of each:
Mammals: Reptiles:

Viperidae (snakes)

Testudinidae (turtles)

Alligatoridae (alligators, caimans)

Crocodylidae (crocodiles)

Animal Genus Types

We've covered animal families, let's move on to animal genus types. A genus is a group of closely related animals within a family. For example, the Panthera genus includes all cats that can roar, such as lions, tigers, and jaguars.

There are over 100 mammal genera and over 200 reptile genera.

Here are a few examples of each:
Mammals:

Panthera (e.g. lions, tigers, jaguars) - large cats that roar

Canis (e.g. dogs, coyotes, foxes)

Bos (e.g. cattle)

Ovis (e.g. sheep)

Reptiles:

Python (e.g. pythons)

Chelonoidis (e.g. turtles)

Alligator (e.g. alligators)

Crocodylus (e.g crocodiles)

Animal Species

Finally, we've arrived at animal species. A species is a group of animals that can mate and produce fertile offspring. For example, lions and tigers are two different species of Panthera.

There are over 5000 mammal species and over 9000 reptile species. Here are a few examples of each:
Mammals:

Panthera leo (lion)

Panthera tigris (tiger)

Bos taurus (cattle)

Ovis aries (sheep)

Reptiles:

Python regius (royal python)

Chelonoidis nigra (black turtle)

Alligator mississippiensis (American alligator)

Crocodylus niloticus (Nile crocodile)

Animal Scientific Classification Chart Example 1 - Capybara

Phylum: Chordata (Vertebrate)

Class: Mammalia (Mammal)

Order: Rodentia (rodent)

Family: Caviidae

Genus: Hydrochoerus

Species: Hydrochoerus hydrochaeris (Capybara)

Animal Scientific Classification Chart Example 2 - Gorilla

Kingdom: Animalia (Animal)

Phylum: Chordata (Vertebrate)

Class: Mammalia (Mammal)

Order: Primates

Family: Hominidae (Great Apes)

Genus: Gorilla

Species: Gorilla gorilla (Gorilla)

Animal Scientific Classification Chart Example 3 - Boa Constrictor

Kingdom: Animalia (Animal)

Phylum: Chordata (Vertebrate)

Class: Reptilia (Reptiles)

Order: Squamata

Family: Boidae

Genus: Boa

Species: Boa constrictor

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Scientific Classification of Animals - Animal Corner

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Did you know that there are over 1.5 million different species of animals on this planet? That's a lot of creatures! It can be difficult to keep track of them all, especially when they all fall into different classification categories.

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Animal Classification - Biology | Socratic

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The best videos and questions to learn about Animal Classification. Get smarter on Socratic.

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Animal Classification for Kids | Learn how to Classify Animals and the Animal Taxonomies

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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.
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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.

On this page we're going to discover how classification helps us to understand the relationships between species and also how different species 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. All of the animals within groups such as these have certain things in common; they are 'related' to each other in some way.

Think of a typical mammal and a typical insect. Now try to list the physical similarities between them. Chances are the list won't be very long; it's clear that the two animals are not closely related.

Now repeat the exercise, either with two mammals or two insects. It's likely that you'll find it much easier to come up with a list of similarities between them.

Mammals and insects are very different animals. Sometimes the differences between animal groups aren't quite so obvious. Crocodiles and alligators, for example, look similar, yet are in different families.

(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 to one another. Yet the dolphin is a mammal, and the shark is a fish.

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

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

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!

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

Taxonomic Ranks

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).

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).

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.

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

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

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.

Kingdom

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).

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

Phylum

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.)

Class

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.)

Order

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.)

Family

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).

Genus

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.

Species

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

Members of the same species are able to reproduce and create fertile offspring (i.e. their babies can also have babies of their own).

Some 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.

Animal Classification Examples Chart

The gray wolf has a large number of subspecies. These include the Eurasian wolf, Arctic wolf, Northwestern wolf, dingo and domestic dog.

For many years, the domestic dog has been selectively bred by man for different roles. As a result of this, there can be a large variation in size and appearance between different dogs - despite their being in the same subspecies. Usually, animal subspecies look very similar to each other!

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

English Name

Gray wolf

Great White Shark

Ostrich

Nile crocodile

Red Eyed Tree Frog

Common Octopus

Man

Species Canis lupus Carcharodon carcharias Struthio camelus Crocodylus niloticus Agalychnis callidryas Octopus vulgaris Homo 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. 16 th 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 17 th 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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Animal Classification For Kids And Students: How We Make Sense Of The Animal Kingdom By Naming And Grouping Species.

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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.

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Guess the animal classification: Vertebrate or Invertebrate?| Game for Kids| Age limit 4-99