Kingdom Animalia: We belong to the Class Mammalia, which comes under the Phylum Chordata of the Kingdom Animalia. The Kingdom Animalia is a huge kingdom that involves many different species. The animal kingdom involves approximately 1.2 million species of animals. Animals are classified based on the level of organisation, body symmetry, germ layers, nature of coelom, segmentation, notochord, etc.

The different phylum of the Kingdom Animalia is Phylum Porifera, Coelenterata (Cnidaria), Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata, and Chordata. In this article, let us learn how animals are classified under different phyla based on their special characteristics and more than 5 Kingdom Animalia examples. Scroll down to learn more!

Define Kingdom Animalia

Kingdom Animalia is characterised by multicellular, eukaryotic animal forms. It is also known as Metazoa. It includes around 1.2 million species of animals, from sponges to mammals.

What is Animalia?

Animalia is one of the fundamental groups of living things that includes all animals or all multicellular animals.

Basis of Classification

Animals are classified based on certain common fundamental features. They are given below:

Level of Organisation

Depending on the organisation of cells, animals are grouped into 2 categories, namely, parazoans (shows cellular level) and eumetazoans (shows tissue level or organ level or organ system level or organisation).
i. Cellular Level – In this, cells are not organised into tissues. They are arranged as loose aggregates.
ii. Tissue Level – In this, cells performing the same functions are grouped together to form tissues.
iii. Organ Level – In this, tissues are joined to form organs, and each organ is specialised to perform a particular function.
iv. Organ System Level – In this, organs become associated to form a functional system where each system is concerned with a specific physiological function.

Body Symmetry

It refers to the similarities with the arrangement of parts on the opposite sides of the body.
i. Asymmetrical Animals – The body cannot be divided into two identical halves along any plane.
ii. Radial Symmetry – If an animal can be cut into two identical along any plane passing through the central axis.
iii. Bilateral Symmetry – If the animal can be cut into two identical halves only along one vertical plane.

Germ Layers

These are the groups of cells behaving as a unit during the early stages of embryonic development. Based on a number of germ layers, animals are placed in two groups, i.e., diploblastic (embryo is two-layered consisting of outer ectoderm and inner endoderm) and triploblastic (embryo is three-layered consisting of outer ectoderm, middle mesoderm and inner endoderm).

Nature of Coelom

Coelom is referred to the body cavity, the space between the body wall and gut wall. Depending on the nature of the body cavity, there are 3 types of animals, namely,
i. Acoelomates – There is no body cavity.
ii. Pseudocoelomates – If the body cavity is not lined by mesoderm and instead mesoderm is scattered as pouches between ectoderm and endoderm.
iii. Eucoelomates or True Coelomates – If the body cavity is lined by mesoderm.

Segmentation of the Body

It is the serial repetition of similar parts along the length of an animal.
i. Pseudo Segmented – The body is divided into several pseudo segments that are independent of each other,
ii. Metameric Linear repetition of body parts.

Notochord

It is a tubular rod-like structure present between the nerve cord and alimentary canal derived from the mesoderm.
Animals with notochord are called chordates and those which do not possess notochord are called non-chordates.

Animal Kingdom Classification Table

The Kingdom Animalia classification is shown below through a flowchart:

Fig: Animal Kingdom Classification

Classification and Characteristics of Kingdom Animalia

The classification and characteristics of each phylum of the Kingdom Animalia are given below:

Phylum Porifera

The members of this phylum are commonly known as sponges. These are pore bearing animals and exhibit the following general characteristics:
1. These poriferans are the most primitive multicellular animals that show a cellular level of organisation.
2. Poriferans bear numerous minute pores called Ostia on the body wall, which lead into a central cavity called spongocoel or perigastric cavity. The spongocoel opens to outside by osculum.
3. They may be solitary or colonial found attached to a substratum leading a sedentary life.
4. Spongocoel and the canals are lined by special cells called choanocytes or collar cells.
5. Digestion is intracellular; respiration and excretion occur through the body wall by diffusion.
6. Reproduction is by asexual or sexual methods.

Phylum Coelenterata (Cnidaria)

Coelenterates are the animals bearing a special body cavity called coelenteron (gastrovascular cavity). They exhibit the following general characteristics:
1. These are multicellular animals with a tissue grade organisation and show radial symmetry.
2. These are sedentary s or-swimming animals and exist either in solitary or in colonial forms.
3. They are diploblastic animals, and their body contains several types of cells known as stinging cells (cnidoblast), interstitial cells (totipotent cells), sensory cells, nerve cells, etc.
4. In coelenterates, the skeleton may be an endoskeleton or exoskeleton.
5. Digestion is both intracellular and extracellular. Respiration and excretion are by diffusion through the body wall.
6. It shows that metagenesis (alternation of generation) and reproduction occur through sexual and asexual methods.

Phylum Ctenophora

The members of this phylum are commonly called sea walnuts or comb jellies. They exhibit the following general characteristics:
1. They are diploblastic animals and acoelomates.
2. They are radially symmetrical with tissue level of organisation.
3. A gelatinous mesoglea is present between epidermal and gastrodermis tissue layers. They are also called comb plates. Colloblast cells are the sensory and adhesive cells.
4. Digestion is both extracellular and intracellular.
5. These are hermaphrodites, and reproduction is only by sexual means.

Phylum Platyhelminthes

The members of this phylum are commonly known as flatworms because of their dorso-ventrally flattened bodies. They exhibit the following general characteristics:
1. They are the first animals to have bilateral symmetry and undergo cephalisation. They are triploblastic animals and show organ system organisation.
2. They are-living forms, and some are parasitic. Most of them are endoparasite and present inside the animals, including man.
3. The digestive system may be present or absent; respiration occurs through the body surface by diffusion.
4. Excretion is by a group of specialised cells called flame cells.
5. These are mostly hermaphrodite and exhibit high power of regeneration.

Phylum Aschelminthes

The members of this phylum are commonly known as roundworms. They exhibit the following characteristics:
1. They are-leaving or parasitic, triploblastic, bilaterally symmetrical and pseudocoelomate organisms.
2. They have a tube-within-tube plan of the digestive system. The excretory system is H-shaped, and contains rennet cells.
3. Sexual dimorphism is present, and males are smaller than females. Fertilisation is internal, and it may be direct or indirect.

Phylum Annelida

The member of this phylum is commonly known as a segmented worm with an annulated or segmented body. They exhibit the following characteristics:
1. They are triploblastic, bilaterally symmetrical with organ system organisation.
2. Annelids are coelomate animals having a fluid-filled cavity between the endoderm and mesoderm and have a closed circulatory system.
3. These animals show metameric segmentation, i.e., the external division of the body by annuli corresponds to the internal division of coelom by septa.
4. Excretion is by nephridia; reproduction is by both sexual and asexual means.

Phylum Arthropoda

It is the largest phylum of the animal kingdom and the members are known as jointed legged animals. They exhibit the following characteristics:
1. Their body is divided into head, thorax, and abdomen.
2. They are haemocoelomates, triploblastic and show organ system level of organisation.
3. Excretory organs are represented by coxal glands and Malpighian tubules.
4. These animals are generally oviparous or ovoviviparous.

Phylum Mollusca

It is the second-largest phylum in the animal kingdom and is commonly known as a soft-bodied animal as they have a soft body enclosed in a calcareous shell. They exhibit the following general characteristics:
1. The body is divided into head, foot and mantle cavity.
2. A peculiar sense organ called osphradium to check water quality.
3. The excretory organ is in the form of structures called organs of Bojanus.
4. Locomotion is by muscular foot, and sexes are usually dioecious, but some are hermaphrodites.

Phylum Echinodermata

The members of this phylum are commonly known as spiny skinned animals due to the presence of numerous spines on their body surface. They exhibit the following characteristics:
1. Adults with pentamerous radial symmetry, while larval forms with bilateral symmetry.
2. These are exclusively marine animals.
3. Head, respiratory pigment, and excretory organs are absent. Reproduction is sexual and shows the great power of regeneration.

Phylum Hemichordata

It includes acorn worms or tongue worms. They are commonly called half chordates or pre-chordates. They exhibit the following characteristics:
1. The body is divided into proboscis, collar and trunk.
2. Respiration by gill slits and excretion by the glomerulus of the proboscis.
3. They mainly reproduce by sexual reproduction.

Phylum Chordata

Animals belonging to phylum–chordata are characterised by the presence of the notochord, dorsal tubular nerve cord, gill clefts and a post-anal tail.

Classification of Chordata

The Phylum Chordata is divided into subphyla, namely, Urochordata, Cephalochordata and Vertebrata. The major classes of Chordata are given below:

Fig: Classification of Chordata

Kingdom Animalia Examples

Let us take a look at a few Kingdom Animalia examples.

Porifera: Examples involve Sycon, Spongilla, Hyalonema, etc.

Coelenterata: Examples involve Hydra, Aurelia, Physalia, etc.

Ctenophora: Examples involve Pleurobrachia, Velamen, etc.

Platyhelminthes: Examples involve Taenia solium, Echinococcus granulosus, etc.

Fig: Platyhelminthes

Aschelminthes: Examples involve Ascaris lumbricoides, Wuchereria bancrofti, etc.

Fig: Ascaris lumbricoides

Annelida: Examples involve Nereis, leech, earthworm, etc.

Fig: Leech

Arthropoda: Examples involve Cockroach, lobster, honey bee, prawn, etc.

Fig: Cockroach

Mollusca: Examples involve Pila, Ostrea, Solen, Doris, etc.

Echinodermata: Examples involve Starfish, Sea urchin, etc.

Hemichordata: Examples involve Balanoglossus, Saccoglossus, etc.

Fig: Balanoglossus

Chordata: Examples involve lamprey, lancelets, dogs, humans etc.

Fig: Lamprey

Economic Importance of Kingdom Animalia

Some of the economic importance of the phyla of the kingdom Animalia are given below:

1. Phylum Porifera: They are used commercially for bathing or cleaning sponges.
2. Phylum Coelenterata: They participate in forming coral reefs, e.g., Millipore. They also have an ornamental value (star coral).
3. Phylum Ctenophora: They reproduce quickly and are good predators.
4. Phylum Platyhelminthes: Fasciola causes fascioliasis or liver rot characterised by hepatitis.
5. Phylum Aschelminthes: Ascaris causes ascariasis in humans.
6. Phylum Annelida: Earthworms are used as fish baits and improve soil fertility.
7. Phylum Arthropoda: Honeybee produces wax and honey. Prawns and lobster are used as food in many countries.
8. Phylum Mollusca: Molluscans like oysters, squid and cuttlefish are used as food in many countries. Sepia ink has medicinal value.
9. Phylum Echinodermata: Eggs of sea urchins are used for embryological studies. Sea cucumber is used as food in many countries.
10. Phylum Hemichordata: They show affinities with echinoderms, annelids and chordates.
11. Phylum Chordata: Many chordates, including fish, chicken, etc., are the source of food for humans. Many mammals are kept as pets and used in daily tasks.

Difference Between Plantae and Animalia

Plantae	Animalia
These do not show locomotion.	They show locomotion.
It includes all eukaryotic photosynthetic organisms.	It includes heterotrophic, eukaryotic, and multicellular creatures.
A cell wall is found in plant cells.	Animal cells do not have a cell wall.
This kingdom’s organisms can prepare their food.	This kingdom’s organisms are unable to prepare their food.
They develop throughout their lifespan.	These can grow up to a particular age only.

Summary

Kingdom Animalia is characterised by multicellular, eukaryotic animals, which are also known as Metazoan. It is a kingdom that involves the largest phylum Arthropoda. Mollusca is known to be the second-largest phylum of the animal kingdom. The Phylum Chordata is divided into subphyla, namely, Urochordata, Cephalochordata and Vertebrata.

All vertebrates are chordates, but all chordates are not vertebrates. Through this article, we understood the different phyla of the Kingdom Animalia and their divisions and class. You can also find articles on other Kingdom Plantae and Animalia on the Embibe app and website.

Learn About Animal Husbandry Here

FAQs on Kingdom Animalia

The frequently asked questions on the

animal kingdom are given below:

Q.1: What are the two classifications of the animal kingdom?
A: The two classifications of the animal kingdom are vertebrates and invertebrates.

Q.2: What are the \(9\) major phyla of Kingdom Animalia?
A: The \(9\) major phyla of Kingdom Animalia are Porifera, Coelenterata, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Chordata.

Q.3: What does Kingdom Animalia consist of?
A: The Kingdom Animalia consists of multicellular eukaryotic organisms that are heterotrophic in nature.

Q.4: What are the \(5\) Kingdom Animalia?
A: The \(5\) animal kingdoms are the Pisces, Aves, Mammalia, Reptilia and Amphibia.

Q.5: What are the 4 characteristics of Kingdom Animalia?
A: The four characteristics of the Kingdom Animalia are as follows:
a. The members of this kingdom are multicellular eukaryotic organisms.
b. They show the heterotrophic mode of nutrition, i.e., depending on other organisms for food.
c. Most ingest food and digest it in an internal cavity.
d. They do not possess a cell wall.

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