Animal Kingdom: Meaning, Classification Chart, Characteristics and Examples

The animal kingdom is home to an incredible variety of animals, each with its own unique features and way of life. Some are so tiny that they can only be seen under a microscope, while others, like whales and elephants, are among the largest animals on Earth. They live all around us, from deep oceans and dense forests to hot deserts, high mountains, and icy polar regions. 

This guide focuses on the animal kingdom, its key characteristics, classification, major phyla, vertebrate classes, and common examples.

Table of Contents

• What is the Animal Kingdom
• Key Characteristics of the Animal Kingdom
• Classification of the Animal Kingdom
• Non Chordates
• Chordates
• Frequently Asked Questions on Animal Kingdom
• Difference between Non Chordates and Chordates
• Animal Kingdom Classification Chart
• Importance of the Animal Kingdom
• Interesting Facts about the Animal Kingdom

What is the Animal Kingdom

The animal kingdom, also known as Kingdom Animalia, includes all animals, from tiny microscopic organisms to large mammals like elephants and whales.

Compared to plants, animals cannot make their own food. Instead, they depend on plants, other animals, or both for nutrition. Interestingly, at some stage of their life, most animals are also able to move.

To better understand this diversity, scientists classify animals into different groups based on the characteristics they share. Features such as body organisation, symmetry, body cavity, segmentation, and the presence or absence of a backbone help group animals in a simple and systematic way.

Key Characteristics of the Animal Kingdom

Although animals differ in their size, shape, and habitat, they share several common features that place them under the animal kingdom. These characteristics make it easier to identify and study different groups of animals.

1. To begin with, animals are multicellular organisms, meaning their bodies are made up of many cells that work together to perform different functions.

2. Another important feature is that their cells are eukaryotic. This means each cell has a well-defined nucleus and other membrane-bound organelles.

3. In addition, animals cannot make their own food. Instead, they depend on plants, other animals, or both to meet their nutritional needs.

4. Animal cells do not have a cell wall. This gives their bodies the flexibility needed for movement and growth.

5. Most importantly, most animals can move from one place to another at some stage of their life. This helps them find food, escape predators, and reproduce.

6. As animals become more complex, their cells form specialised tissues, organs, and organ systems that work together to carry out functions such as digestion, respiration, circulation, and reproduction.

7. Finally, most animals reproduce sexually, producing offspring with traits inherited from both parents. However, some simpler animals can also reproduce asexually.

Also Read: Vertebrates and Invertebrates

Classification of Animal Kingdom

One of the easiest ways to classify them is by checking whether they have a notochord, a flexible supporting rod found during development. 

Based on these criteria, the animal kingdom is divided into two main groups: non-chordates and chordates.

Let's first learn about non chordates, which make up nearly 95% of all animal species.

1. Non Chordates

Non chordates are animals that do not have a notochord or backbone. This group includes a wide range of animals, from simple sponges to insects and starfish. 

To make them easier to study, scientists have divided non chordates into different phyla based on their body structure and other common features.

Phylum	Main Features	Common Examples
Porifera	The simplest animals with tiny pores all over the body. They mostly live in water and remain fixed in one place.	Sponge, sycon, spongilla
Cnidaria (Coelenterata)	Aquatic animals with stinging cells and tentacles around the mouth. Most have radial symmetry.	Hydra, jellyfish, sea anemone, coral
Platyhelminthes	Flat bodied worms. Many of them are parasites that live inside other organisms.	Tapeworm, liver fluke, planaria
Nematoda (Aschelminthes)	Round, cylindrical worms with a complete digestive system.	Roundworm, hookworm, pinworm
Annelida	Worms with a segme1nted body and a well-developed circulatory system.	Earthworm, Leech, Nereis
Arthropoda	The largest animal phylum. These animals have jointed legs, a hard outer covering, and a segmented body.	Butterfly, cockroach, spider, crab, honeybee
Mollusca	Soft-bodied animals, many of which have a shell and move using a muscular foot.	Snail, octopus, oyster and squid
Echinodermata	Marine animals with spiny skin and a unique water vascular system used for movement.	Starfish, sea-urchin, sea-cucumber

Now that you have learned about non chordates, let's move on to the second major group in the animal kingdom, the chordates. 

2. Chordates

These animals have a notochord, which is a flexible supporting rod present at some stage of their life. In most vertebrates, this notochord later develops into the backbone. Chordates include many familiar animals, such as fishes, amphibians, reptiles, birds, and mammals.

Here are some common characteristics of chordates:

Even though chordates live in different habitats and vary in appearance, they share a few common features. 

They have a notochord during development, a dorsal hollow nerve cord, gill slits at an early stage, a post-anal tail and bilateral symmetry. 

Based on these characteristics, chordates are further divided into five major vertebrate classes.

a. Pisces

The first class is Pisces, which includes all fishes. These animals spend their entire lives in water and are well adapted to aquatic habitats. They breathe through gills, swim using fins, and are cold-blooded.

Examples: Rohu, shark, tuna

b. Amphibia

The next class is Amphibia. These animals spend part of their lives in water and the rest on land. Young amphibians breathe through gills, while adults develop lungs. Their moist skin also helps them breathe.

Examples: Frog, salamander, toad

c. Reptilia

Reptilia includes animals that are mainly adapted to life on land. Their dry, scaly skin protects their bodies and helps reduce water loss. They breathe through lungs, are cold-blooded, and most species lay eggs.

Examples: Snake, crocodile, lizard, turtle

d. Aves

Aves is the group that includes all birds. Their bodies are covered with feathers, and their forelimbs are modified into wings. Although many birds can fly, some, like penguins, cannot. Birds are warm-blooded and have a four-chambered heart.

Examples: Eagle, sparrow, peacock, penguin

e. Mammalia

The final class is Mammalia. Mammals are known for feeding their young with milk produced by mammary glands. They have hair or fur, are warm-blooded, and can be found in a wide variety of habitats across the world.

Examples: Human, elephant, tiger, whale, bat

Also Read: Five Kingdoms Classification

Difference between Non-Chordates and Chordates

One of the simplest ways to group them is by checking whether they have a notochord, a flexible supporting rod found during development. 

Based on this feature, animals are divided into non-chordates and chordates.

Feature	Non-Chordates	Chordates
Notochord	Absent	Present during at least one stage of life
Backbone	Usually absent	Present in vertebrates
Nerve cord	Located on the underside (ventral)	Located along the back (dorsal)
Heart	Usually on the upper side (dorsal)	Located on the lower side (ventral)
Examples	Earthworm, butterfly	Fish, birds, humans

Animal Kingdom Classification Chart

The animal kingdom is divided into different groups based on shared characteristics such as body structure, habitat, and level of organisation. 

The chart below gives a quick overview of the major phyla and vertebrate classes along with their key features and common examples.

Group	Main Feature	Examples
Porifera	The body has tiny pores	Sponge
Cnidaria	Stinging cells present	Hydra
Platyhelminthes	Flat-bodied animals	Tapeworm
Nematoda	Cylindrical or round body	Roundworm
Annelida	Segmented body	Earthworm
Arthropoda	Jointed legs and exoskeleton	Butterfly
Mollusca	Soft body and often comes with a shell	Snail
Echinodermata	Spiny skin and marine habitat	Starfish
Pisces	Aquatic vertebrates with gills	Shark
Amphibia	Live on both land and in water	Frog
Reptilia	Dry, scaly skin	Snake
Aves	Feathers and wings	Sparrow
Mammalia	Hair or fur and mammary glands	Human

Quick Tip: 

A simple way to remember the animal kingdom classification is to first learn the eight major non-chordate phyla, followed by the five vertebrate classes of chordates. This makes it easier to understand how different animals are grouped and related.

Importance of the Animal Kingdom

Every species, from the smallest insect to the largest mammal, plays a unique role in keeping nature balanced. In addition to supporting ecosystems, animals also contribute to agriculture, medicine, and our everyday lives.

Here are some of the key reasons why the animal kingdom is important:

1. First, animals help maintain food chains and food webs, ensuring that ecosystems remain balanced.

2. They also support plant growth by pollinating flowers and dispersing seeds to new areas.

3. In addition, many animals naturally keep pest populations under control, helping protect crops and forests.

4. As animals feed and decompose, they recycle nutrients back into the environment, enriching the soil and supporting new life.

5. Beyond their ecological role, animals provide food, clothing materials, medicines, and several other useful resources.

6. They also play an important part in scientific and medical research, helping researchers develop new treatments and technologies.

7. Most importantly, animals contribute to biodiversity, making ecosystems healthier, stronger, and more resilient.

Interesting Facts about Animal Kingdom

• The animal kingdom contains more than 1.5 million identified animal species, with millions more believed to exist.
• Arthropods account for the largest number of animal species.
• The blue whale is the largest animal ever known to have lived on Earth.
• Sponges are among the oldest multicellular animals.
• Bats are the only mammals capable of sustained flight.
• Octopuses have three hearts and blue blood.
• Some jellyfish species can regenerate damaged body parts.

Till now, you have seen how different animals are grouped based on their common features. Learning this classification makes it easier to identify different types of animals and understand how they are related.