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Animal Kingdom

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Introduction to Animalia

All creatures are members of the Kingdom Animalia, also called Metazoa. This Kingdom doesn't contain prokaryotes (Kingdom Monera, which includes bacteria, blue-green algae) or protists (Kingdom Protista, which includes unicellular eukaryotic organisms). All members of Animalia are multicellular, and all are heterotrophs (that is, they calculate directly or laterally on other organisms for their ailment). Most ingest food and digest it in an internal depression. 

It's estimated that around 9 or 10 million species of creatures inhabit the earth; the exact number isn't known and all estimates are rough. Creatures range in size from no further than many cells to organisms importing numerous tons, similar to blue jumbos and giant squid. By far most species of creatures are insects, with groups similar as molluscs, crustaceans, and nematodes also being especially different. By this measure, our own group, the invertebrates, is fairly inconsequential from a diversity perspective.

R.H. Whittaker organized organisms into five kingdoms. He classified organisms supported cell structure, mode, source of nutrition and body design. The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae, and Animalia. Let us learn about the animal kingdom, i.e., Kingdom Animalia.

Kingdom Animalia

Kingdom Animalia constitutes all animals. Amongst the five kingdoms, the most important kingdom is Animalia. Animals are multicellular eukaryotes. However, like plants, they do not possess chlorophyll or a cell membrane. Therefore, members of the Animalia exhibit a heterotrophic mode of nutrition. Kingdom Animalia has been classified into ten different subphyla supported their body design or differentiation.

The different phylum of the Animalia are as follows:

  1. Porifera

  2. Coelenterata (Cnidaria)

  3. Platyhelminthes

  4. Nematoda

  5. Annelida

  6. Arthropoda

  7. Mollusca

  8. Echinodermata

  9. Hemichordata

  10. Chordata

Phylum Porifera

Porifera means organisms with holes. They are commonly known as Sponges. Features of the Porifera are:

  1. Non-motile, multicellular organisms with a hard outer skeleton.

  2. Have a porous body.

  3. Pores on the bodies create a canal system that helps in the circulation of drugs.

  4. Their body does not include a typical head and tail; well-developed organs or organ systems are absent.

  5. Include marine habitat.

Example of phylum Porifera includes- Spongilla, Sycon.

Phylum Coelenterata (Cnidaria)

The term Coelenteratais derived from the Greek word “kilos” which suggests hollow-bellied. Their features are:

  1. Have a hollow body cavity.

  2. The body is differentiated into two ends.

  3. Includes all aquatic animals.

  4. The body is formed of two layers of cells: inner and outer linings.

  5. They are either found solitarily (Sea anemone) or in colonies (corals).

Example of phylum Coelenterata includes – Hydra, Jellyfish.

Phylum Platyhelminthes

Platyhelminthes are commonly known as flatworms. Their features are:

  1. Dorsoventrally flattened body.

  2. Complex and have differentiated body structure.

  3. They are triploblastic, i.e. tissue is differentiated from three distinct cell layers.

  4. Do not have a real internal cavity or coelom.

  5. Have bilateral symmetry.

  6. Either free-living (Planaria) or parasitic (liver flukes).

Example of phylum Platyhelminthes includes -Tapeworm, Planaria.

Phylum Nematoda

Phylum Nematoda consists of nematodes or roundworms. Their features are:

  1. Nematodes have a cylindrical body.

  2. Bilaterally symmetrical and triploblastic.

  3. Have pseudocolour, a false body cavity.

  4. Parasitic and causes diseases such as elephantiasis, ascariasis.

Example of phylum Nematoda includes – Ascaris, Wuchereria.

Phylum Annelida

Annelids are commonly referred to as segmented or ringed worms. They have the following features:

  1. Have a segmented cylindrical body.

  2. The body is differentiated into the head and tail.

  3. Bilaterally symmetrical and triploblastic.

  4. Have a true body cavity.

  5. Habitat: marine, freshwater, and land.

Example of phylum Annelida includes – Earthworm, Leech.

Phylum Arthropoda

Arthropod means jointed legs. Animals that have jointed appendages belong to the present phylum. This is the most important phylum within the Animalia. Other features are:

  1. They are bilaterally symmetrical.

  2. Have jointed appendages, exoskeleton, and a segmented body.

  3. Have a well-differentiated organ and organ system.

  4. Have an open cardiovascular system, but don't have differentiated blood vessels.

Examples include – butterflies, spiders and mosquitoes.

Phylum Mollusca

Phylum Mollusca consists of an outsized group of animals. Features are:

  1. Bilaterally symmetrical and triploblastic.

  2. Less segmented body.

  3. Well-developed organ and organ system.

  4. Typically, an open circulatory system is present.

  5. Limbs are present.

Example of phylum Mollusca includes- Snails and octopus.


Phylum Echinodermata

The term Echinodermata springs from the Greek words, ‘echinos’ meaning hedgehog and derma meaning skin. Thus, echinoderms are spiny-skinned animals.

  1. Radial symmetry and triploblastic.

  2. Have true coelom.

  3. Have a hard calcium carbonate skeleton structure.

  4. Free-living marine animals.

Example of phylum Echinodermata includes- Sea urchins, starfish.

Phylum Hemichordata

The characteristics of the phylum Hemichordata are as follows:

  1. Soft and fragile body divided into a proboscis.

  2. The epidermis is single-layered.

  3. Includes marine animals (worm-like) with an organ-system organization level.

  4. They have an open circulatory system.

  5. They respire through gills since they are marine.

  6. Sexes are separate and fertilization is external.

  7. Development is direct.


Phylum Chordata

The Chordates possess the following characteristics:

  1. Body bilaterally symmetrical, with an organ-system organisation level and are triploblastic.

  2. They possess a notochord and a nerve cord.

  3. The circulatory system is closed type.

Phylum Chordata is often divided into the subsequent sub-phyla:

  • Urochordata

  • Cephalochordata

  • Vertebrata

Hence Animalia is the largest kingdom amongst the five kingdoms consisting of all animals. Animals are multicellular eukaryotes; don't possess a cell membrane or chlorophyll like plants, and share an equivalent mode of nutrition, that is, the heterotrophic mode. Among the other prominent characteristics of this kingdom include body symmetry, cell arrangement, extent of organization, presence/absence of notochord, etc.

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FAQs on Animal Kingdom

1. What is the System of Classification in Animal Kingdom?

There are a good number of animals that can be compared and distinguished from each other by numerous angles. Individuals from a selected group of animals share a selected trademark that's typical of each one among the individuals from that group. This is the component that characterizes the group.

Kingdom –  Kingdom is the most astounding essential division during which all articles are set. Animal Kingdom involves all animals in the world.

Phylum – In this, each kingdom is separated into smaller subdivisions called phyla. 

Class – Chordates are further separated into classes, For example, Mammalia, Birds, Reptilia, and Amphibians. Individuals from every class have attributes that they communicate to the individuals from an equivalent class yet aren't found in individuals from different classes.

Family – Classes further are separated into families. Families contain more than one genus.

Genus – Families are sub-partitioned into genera. Animals that have an equivalent genus are fundamentally equivalent as and presumably developed from an equivalent common predecessor.

Species – Species is the most vital and contains just one animal.

2. What is an Animal Cell?

Animal cells warrant the rigid cell walls that characterize factory cells. The bodies of utmost creatures (all except bloodsuckers) are made up of cells organized into apkins, each towel specialized to some degree to perform specific functions. In the utmost, apkins are organized into indeed more technical organs. Most creatures are capable of complex and fairly rapid-fire movement compared to shops and other organisms. Utmost reproduce sexually, by means of discerned eggs and sperm. Most creatures are diploid, meaning that the cells of grown-ups contain two clones of the inheritable material. The development of utmost creatures is characterized by distinctive stages, including a zygote, formed by the product of the first many division of cells following fertilization; a blastula, which is a concave ball of cells formed by the developing zygote; and a gastrula, which is formed when the blastula crowds in on itself to form a double-walled structure with an opening to the outside, the blastopore.

3. What is the Monera Kingdom?

This is the area of bitsy living effects and groups together the prokaryotes (archaea and bacteria). This group is present in all territories and is made up of single-cell effects with no defined nexus. Most bacteria are aerobic and heterotrophic, while the archaea are generally anaerobic and their metabolism is chemosynthetic. 


The bracket of the five fiefdoms of nature remains the most accepted moment, although the rearmost advances in inheritable exploration have suggested new variations and restarted the debate among experts. Similar is the case for the sixth area of Carl Woese and George Fox, who in 1977 divided bacteria into two types (Archaea and Bacteria), and the seventh area of Cavalier-Smith, who added a new group to the former six for algae called Chromista.

4. State the characteristics of the Animal Kingdom?

Though there's great diversity in the beast area, creatures can be distinguished from the other fiefdoms by a set of characteristics. Though other types of life may partake some of these characteristics, the set of characteristics as a whole gives a distinction from the other fiefdoms. 

  • Creatures are multicellular.

  • Creatures are heterotrophic, carrying their energy by consuming energy-releasing food substances. 

  • Creatures generally reproduce sexually. 

  • Creatures are made up of cells that don't have cell walls.

  • Creatures are able to stir in some stage of their lives.

  • Creatures are suitable to respond snappily to external stimulants as a result of whim-whams cells, muscle or contractile towel, or both.

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