The Kingdom Animalia is a big group that consists of eukaryotic, multicell organisms that space heterotrophic in nature. As such, they achieve their nutrition from external sources. Although they are unable to create their own food, which is one of the key defining features of plants, animal cells lack a cell wall that is present in tree cells.

With the exception of a couple of animals, the majority of pets are motile which enables them to efficiently respond come stimuli and also find food, etc. In general, animals are split into 2 main teams namely, vertebrates (animals with a backbone) and also invertebrates (animals that lack a backbone). However, lock are additionally divided into several phyla that will certainly be discussed below in detail. 


Some examples of pets include:


Human beings CowsFishBirdsSponges - InvertebrateLobster - InvertebrateSpiders - InvertebrateClams - Invertebrate


Kingdom Animalia Classification

As mentioned, all pets are split into two main categories/groups: vertebrates and also invertebrates



Vertebrates incorporate all animals classified under the subphylum Vertebrata. Castle belong come the phylum Chordata and possess a backbone/vertebrae (where the spinal cord is located). They are likewise characterized by an inner skeletal system on i beg your pardon muscles room attached.

Vertebrate pets are classified into seven main classes the include:


The majority of species are characterized by epidermal hair and also the females offer birth and also suckle the young. However, duck-billed and also spiny anteater put eggs. 

Aves/Birds - pets that are identified by wings, feathers, and also a beak. Reproduction requires laying egg that vary in size depending upon the kind of bird. Examples of birds incorporate kiwi, emu, chicken, and also woodpecker among others. Part birds have actually wings however cannot fly. Top top the other hand, some pets like bats have actually wings yet are classified together mammals. Therefore, not all animals that fly room classified together birds.

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Reptiles (cold-blooded) space four-legged animals and are defined by the visibility of a tail and dermal scales. Because that the majority of species, eggs are fertilized internally resulting in direct development of the organism. Reptile examples include turtles, snakes, and also crocodiles among others. 


Examples the Amphibia through Prehistoricplanes / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Amphibians encompass cold-blooded animals that spend part of their resides in water. While they have the right to absorb oxygen through their skin in a moist environment, some species (or in some phase of their life) have gills offered to breathe in water. They can likewise breathe using lungs top top land. They put jelly-like eggs in moist settings or in water and also include frogs and salamanders etc.


This group is composed of jaw-less pets that look favor fish. Some of the species like Lampreys are characterized by a big head, a notochord, and a sensory system. 


Example that Osteichthyes by Prehistoricplanes / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Osteichthyes space true fish and also are frequently referred to as bony fish. As such, they are characterized by bone organization (rather 보다 cartilage). Few of the other characteristics linked with this group include fused teeth, lobed fins, and a skull. Members of this group encompass clownfish and also ray-finned fish amongst others.

Chondrichthyes by Prehistoricplanes - own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=84071029

Chondrichthyes consists of organisms v a cartilaginous skeleton and also are thus known together cartilaginous fishes. While a couple of species have actually been established in freshwater environments, the bulk of varieties are discovered throughout the ocean. 

Given the vertebrate pets comprise a single phylum, they make up less than 5 (5) percent that all known animals.


While vertebrates comprise of only one phylum, invertebrates comprise the remaining phyla that the kingdom Animalia. As the name suggests, invertebrates absence a backbone and internal skeletons. Few of the species have an exterior skeletal system, the exoskeleton, that offers structural support. Currently, invertebrates are suggested to make up over 97 percent of all animals in the pet kingdom. 

Being such a diverse group, invertebrates are classified based upon a number of characteristics consisting of morphology/structure, symmetry and life cycle, etc.

Whereas few of the organisms have three human body layers, rather (primitive invertebrates) only have two human body layers. Instances of invertebrate pets include insects (like spiders and ticks), snails, sea stars, sponges, and also hydra, etc. 

Jellyfish, Invertebrate picture by Pexels indigenous Pixabay

Levels the Organization

While all animals within the kingdom Animalia space multicellular organisms, they exhibit various patterns of cell organization. Because that this reason, they are also classified based upon the level of organization of their cells. 

Here, they are divided into three main levels i m sorry include:


Cellular level - The cells of pets at this level that organization kind loose aggregates. When the cell of these pets (e.g. Sponges) are committed in a path that allows them to perform various functions, cells that are similar are not organized together to form tissue.

For this reason, the body of this organisms are loose aggregations that consist the different varieties of cells. When the cell in these organisms room not have to organized into tissue, it"s worth noting that several of the cells (e.g. Pinacocytes) kind layers and also serve offered functions.


Tissue level the organization - pets with this level that organization have actually cells that perform the exact same functions and are arranged with each other to kind tissue. For the majority of these organisms, the body is composed of two key layers that room separated by a middle layer known as mesogloea (the middle/third layer is non-cellular).

Being diploblastic (consist that two main layers the cells), this organism is composed of an external layer recognized as the ectoderm, consisting of the epidermis, and the within layer the lines the inner part of the body well-known as the endoderm (making up the gastrodermis). The body additionally consists of an inner body cavity. 


Organ system level that organization - for organisms with this level the organization, the tissues space arranged together to form organs.

While every the cells in the organ may not do the same functions, they are related and also contribute come the purpose of the organ. Few of the organisms with this level of organization include much easier organisms favor Platyhelminthes and also other biology of the higher phyla (human beings etc).

Here, organs are likewise connected in one organ mechanism and function together. A good example of this is an organ device that consists of the kidneys, bladder, and also the ureter creating a functional urinary system. While each of the organs has a different function, they space all connected in the removed of waste material from the body. 


In addition to the level of organization, animals are also classified based on body the contrary (arrangement the the components of the body about the central point). 

While few of the organisms space asymmetrical, and also can as such not be separated into 2 equal or similar halves along the central plane, others room symmetrical whereby the two halves will be equal/similar once the human body is divided into two parts along the central plane. 

Generally, the bulk of organisms at the cellular level the organization have been shown to it is in asymmetrical while those at the tissue/organ level of company are either radial or bilaterally symmetrical.

For animals that exhibition bilateral the contrary (e.g. Person beings, butterfly, dogs, etc), splitting the organisms right into two halves from the head to the tail along the central part will an outcome in two equal halves. Each fifty percent will be a mirror photo of the other. 

An image representing bilateral symmetry. The red line dividing the insect right into two halves shows just how each fifty percent is a mirror photo of the other half. Credit: gimpppa.org

Several pets have radial symmetry and also can, therefore, have plenty of lines of symmetry. Due to the fact that they have several parts arranged roughly the central point, they deserve to be divided along several lines and be nearby showing division resulting in halves that space mirror photos of the various other half.

Some the the organisms with radial symmetry encompass corals, sea anemones, and also jelly fish among others.

Unlike pets with bilateral symmetry, those with radial symmetry can be separated along several lines. The complying with image displayed radial symmetry of a starfish. Credit: gimpppa.org

Compared to pets that are defined by bilateral symmetry, a good number the these pets (with radial symmetry) execute not have bodies with unique fronts (head parts) and also ends. Rather, your bodies room mostly identified by top and bottom sides through various important organs being located on these sides.

The mouth part of a starfish is situated at the main part that the lower or bottom surface. Lock are frequently found in aquatic settings where they feed on food material yielded by water currents. 

While a an excellent number the animals, particularly those with a tissue or organ level the organization, are identified by a radial or bilateral symmetry, part animals, particularly those through a moving level of company (e.g. Sponges) often tend to it is in asymmetrical and also therefore can not be divided into two equal halves. Most of this organisms are simple with a basic body plan because the cells are not organized into tissue or organs. 


Diagrammatic depiction of a sponge – by looking in ~ this image, it"s evident that it cannot be split into two equal halves. Together such, it"s asymmetrical.

Diagrammatic depiction of a sponge, Asymmetrical. Credit. gimpppa.org

Body Cavity/Coelom

Animals are also classified on the communication of human body cavity (coelom). This cavity is typically formed during embryo development. Unlike the gut, which is composed of the endoderm, the coelom is surrounding by the mesoderm.

For this reason, the bulk of pets with a coelom have a mesoderm. It"s located in between the body wall surface of an organism and also the alimentary canal. Some instances of these cavities in the body include the peritoneal cavity and the an are around the lungs. 

Some the the main attributes of this cavity include:


· Protecting organs from mechanical shock

· specifies the form of some organisms and likewise contributes to locomotion 

· connected in the carry of gases, nutrients, and waste material

· offers a room required for advance and functions of offered organs


Based ~ above the body cavity, animals are classified right into the adhering to groups:


As the surname suggests, acoelomates are animals that absence a true human body cavity. The bulk of these animals are simple organisms including members of the phylum Platyhelminthes.

Because they absence a true human body cavity, the mesodermal organization plays vital role in holding provided tissue or guts in place. Acoelomates incorporate a selection of animals including some of those through radial and also bilateral symmetry and asymmetric animals. 

See likewise Helminths.

Pseudocoelomates (animals that have a false coelom)

While organisms classified in this group have a body cavity, the cavity is not obtained from the mesoderm. For this reason, the cavity is frequently referred to together a false coelom. Some of the many pseudocoelomates encompass rotifers and nematodes. The body cavity of this organisms is recognized as pseudocoel (and for this reason the surname pseudocoelomates) and includes animals with bilateral symmetry. 

In enhancement to a few mesenchyme tissue, this cavity may consist of fluid or a gelatinous substance. Several of the main features of pseudocoel encompass those associated with digestion, reproduction, and also distribution of nutrients in the body. Few of the other organisms classified as Pseudocoelomates incorporate members that the groups Loricifera, Gastrotricha, and Entoprocta. 

See likewise Nematology.


Coelomates include animals with a true coelom. The bulk of these organisms are identified by a tissue or organ mechanism of organization and also have bilateral symmetry. Unequal Pseudocoelomates, coelomates have actually a coelom the is fully or fully derived native the mesoderm.

As a an are that is located in between the body wall and the gut in every vertebrates, it"s enclosed in between two types of cell (cells that underlie the body wall and those the surround the gut).

Coelomate invertebrates, ~ above the various other hand, room triploblastic and are identified by 3 cellular human body layers that incorporate the ectoderm, mesoderm, and endoderm.

Although it"s located between the body wall surface and the gut, it"s precious noting that this cavity is not in direct call with either. Rather, it"s separated indigenous the 2 by the peritoneum (peritoneal epithelium).

The following is a diagram model of a mollusk (phylum Mollusca) showing ar of the coelom:


* As the coelom rises in size, contact in between the body wall and the peritoneum increases.

Diagram design of a mollusk showing location of the coelom. Credit: gimpppa.org

Different Phylum under the Kingdom Animalia

In biology, a Phylum is a taxonomic category/level the ranks listed below Kingdom but over Class. It"s crucial category that groups organisms based on a set of attributes that collection them personally from various other organisms. 

In the Kingdom Animalia, pets are split into a total of eleven (11) Phyla that include:


Kingdom Animalia: Phylum Chordata

The surname Chordata comes from the Greek indigenous "Chorde" meaning cord or string and also "ata" which method bearing. Therefore, chordates (members of the Phylum Chordata) are pets that have actually a notochord/cord at some suggest of their lives.

While the bulk of animals in the Phylum Chordata have a vertebrate (the bulk of greater animals), the group additionally consists the protochordates (e.g. Squirts and amphioxus) i beg your pardon are carefully related come vertebrates. If they absence a backbone i beg your pardon is present in every vertebrates, these organisms have actually a dorsal nerve cord and also a notochord and also thus qualify to be classified under the Phylum Chordata. 

Currently, there space an approximated 65,000 chordate species. If there are not plenty of when contrasted to some of the various other groups, they exhibit an excellent diversity and also can be uncovered in a variety of habitats, in aquatic and also terrestrial environments, across the world. 

Some instances of chordates include:




Main attributes of Chordates


· bulk of these organisms have an anterior finish that might consist the a head or cephalic region and a posterior finish that consist of a tail in a bulk of animals

· Bilateral symmetry

· majority of animals are triploblastic and also thus have the 3 germinal layers (ectoderm, endoderm, and also mesoderm)

· have actually a coelom

· characterized by an organ-system level the organization 

Kingdom Animalia: Phylum Porifera


The Phylum Porifera consists of few of the earliest well-known animals. Castle are generally found in aquatic environments (particularly in naval environments) where they feeding by filtering water in order to trap and also capture essential material. Organisms prefer Sponges space filter feeders and have been presented to be qualified of catching around 70 percent of rely bacteria and organic issue in your surroundings. 

For the many part, members of this Phylum are basal animals characterized by a cellular level that organization. As such, they absence true tissue offered that cells room not organized right into tissue systems.

Because they lack true tissues, and thus body organ systems, members that the Phylum room generally defined by one aquiferous system that is composed of canal networks and also chambers that enable water to flow in and also out. 

Some organisms that belong to the Phylum Porifera include:


DemospongeCalcareous spongeSiliceous spongeHexactinellid sponge


Kingdom Animalia: Phylum Platyhelminthes


The Phylum Platyhelminthes encompass organisms recognized as flatworms. They are dorsoventrally flattened worms and also thus lack a coelom. The room between body organs is therefore filled v mesenchyme. Back they have a tissue/organ device level of organization (e.g. Have actually a reproductive system), they lack a circulatory system, a respiratory system, and a true anus.

Like few of the other animals, this organisms room triploblastic and also therefore have actually three embryonic cabinet layers (the ectoderm, endoderm, and also mesoderm). They are likewise bilaterally symmetrical and can, therefore, be divided into two equal halves native head come tail.

While few of the biology (e.g. Members that the class Turbellaria) can survive in excessive environmental problems (in sand and rocks etc), the bulk of flatworms have the right to be discovered in aquatic and also moist environments. 

Some the the organisms the belong to the Phylum Platyhelminthes include: 


·  Turbellaria (e.g. Gyratrix hermaphroditus, Pseudoceros dimidiatus, Girardia tigrina) 

· Trematoda (e.g. Clonorchis sinensis, Schistosoma japonicum, and also Metagonimus yokogawai etc) 

· Cestoda (e.g. Pork tapeworm, fish tapeworm, and Taenia taeniaeformis etc). 


Kingdom Animalia: Phylum Cnidaria


Also known as Coelenterata, the Phylum Cnidaria consists of organisms the are typically found in maritime environments. However, a couple of species, prefer Hydra, can be found in freshwater environments.

While there room many species of the Phylum Cnidaria, castle all have actually a an easy body framework that is composed of two cellular layers (endoderm and the ectoderm). These layers space separated by the mesoglea i beg your pardon is a non-cellular, gelatinous layer.

Although they are simple organisms, they have true tissues consisting of the epithelial tissue, muscular tissue, and connective tissue, etc. However, they carry out not have actually an organ level that organization and are thus classified in the tissue grade. Since of their general morphology, they have actually radial symmetry and can, therefore, be separated along several planes. 

Some the the types that belong to the Phylum Cnidaria include:


HydroidsCoralsJelly-fishesSea anemonesPolyps

Kingdom Animalia: Phylum Annelida

Members that the Phylum Annelida, recognized as annelids, space segmented worms found in assorted habitats, in aquatic and also terrestrial environments. While castle exhibit far-reaching diversity through regards to the body plan, studies have revealed the the bulk of types are coelomate and thus have actually a body cavity. 

They are additionally characterized through multiple body segments through the an initial segment (prostomium) consist of of the mind in many of the organisms. The body of this organisms deserve to be split into three main regions consisting of the prostomium (the head part of the body), the stems which consists of multiple segments, and the pygidium i beg your pardon is the post-segmental region. They also contain several internal organs that consist of the cradle system and also circulatory system etc. 


* Annelids also display bilateral symmetry. 


Some the the varieties that belong come the Phylum Annelida include:


EarthwormSludge wormMedicinal leechLugwormSalinera


Kingdom Animalia: Phylum Mollusca

Members the the Phylum Mollusca (mollusks) are coelomate organisms the exhibit bilateral symmetry. However, some of the varieties exhibit asymmetrical conditions after that in life. They usually have actually a soft body that might be safeguarded by a calcareous shell relying on the organism. The ventral part of the body of mollusks consists of a muscular system used because that locomotion. 

Generally, the bulk of this organisms are aquatic and also can, therefore, be discovered in marine and freshwater atmospheres (a few species are uncovered in freshwater). However, some of the types can additionally be found in terrestrial environments. 

Some the the various other characteristics associated with mollusks include:


· are triploblastic and also therefore have three primary layers

· have an organ device level that organization 

· human body cavity (the true coelom) is limited to the pericardial cavity as well as lumen the the gonads

· have an open circulatory system 

· Organs the are distinctive to mollusks incorporate the radula (a feeding structure) and also the mantle (a dorsal layer)



Some the the types that belong come the Phylum Mollusca include:


Giant clam Pacific oystersHard clam Garden snail Freshwater pearl mussel 


Kingdom Animalia: Phylum Arthropoda

Members of the Phylum Arthropoda are well-known as arthropods. Return they space invertebrates, arthropods have actually an exoskeleton that gives structural assistance to the organism. Generally, arthropods are characterized by a segmented human body (consisting the a head, thorax, and also abdomen) and jointed appendages. 

Currently, it"s approximated that there are over one (1) million species of the Phylum Arthropoda making it one of the largest teams of the animal kingdom. Over 80 percent that all pets on earth are arthropods. All arthropods have a true coelom that is tiny in size. 

They likewise exhibit an organ system level of organization with organs developing various body organ systems including the cradle system, circulatory system, and also the worried system, etc. They also exhibit bilateral symmetry where the body deserve to be divided into 2 equal halves. 

Some the the organisms that belong to the Phylum Arthropoda include:




Kingdom Animalia: Phylum Hemichordata

Members that the Phylum Hemichordata (Hemichordates) room worm-like invertebrates generally found in maritime environments. Your bodies are split into three main parts consisting of the proboscis, the collar (mesosome), and also the stems (posterior part of the body). 

They exhibition bilateral symmetry and thus the body can be separated into two equal halves. Due to the fact that they re-superstructure several features with chordates and also members the the Phylum Echinodermata, Hemichordates space sometimes considered to it is in the link in between vertebrate and also invertebrate animals.

Like few of the various other organisms, members the this team (especially adult organisms) have coeloms, but lack properly emerged organ solution as those discovered in most higher animals. 

Some that the animals classified under the Phylum Hemichordata include:


Planctosphaera pelagicaPtychodera flavaSpartobranchus tenuisGlossobalanus minutus


Kingdom Animalia: Phylum Echinodermata


The surname Echinodermata is acquired from the Greek words "echinos" which way spiny and also "Dermos" which way skin. Therefore, together the name suggests, this organisms are identified by a spiny skin. 

Members the this group (echinoderms) are generally found in maritime habitats where they feed on seaweed. Castle are additionally described together invertebrate coelomates given that they have a spacious coelom located in between the gut and body wall. 

They exhibition an organ system level of organization and posses various necessary structures consisting of a mouth and also a finish digestive system. Return they deserve to reproduce sexually, they are likewise capable that regeneration. 

Some the the types classified under this phylum include:


Common starfish Green sea urchinEchinus esculentus Blue sea star ArkaruaProtoreaster nodosus 


Members the this group normally exhibit radial symmetry


Kingdom Animalia: Phylum Ctenophora

Members of the Phylum Ctenophora are generally referred to together Ctenophores. They room invertebrate organisms frequently found in maritime waters throughout the globe. Ctenophores are jelly-like organisms identified by a soft-body that exhibits biradial symmetry.

Like Platyhelminthes and members the the Phylum Cnidaria, Ctenophores space acoelomate and thus absence a true body cavity. Members the this group are additionally characterized by comb rows (eight in total) provided for movement. 

Some of the organisms the belong to this phylum include:


Beroe ovataPleurobrachia bacheiBeroe cucumisXanioascusCtenorhabdotus capulus


Kingdom Animalia: Phylum Aschelminthes

Aschelminthes are aquatic organisms that are bilaterally symmetrical and also exhibit an organ-system level the organization. They space triploblastic and therefore have actually three germinal class (ectoderm, endoderm, and mesoderm).

Although they have actually a flattened, worm-like body, researches have shown them to it is in pseudocoelomate (which originates indigenous the blastocoel) and therefore execute not have actually a true body cavity. They lack the respiratory and circulatory system typically found in other pets but have actually a digestive tract.

Some that the types that belong come this Phylum include:


Horsehair wormsTrichinella spiralisLoriciferaLoa loa

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Joshua Bishop Roby. (2009). Animal Kingdom. 

Kevin Pang and also Mark Q. Martindale. Ctenophores. 

P.S. Verma and also S. Chand. (2013). Chordate Zoology.

See more: What Fruit Is Bigger Than A Watermelon ? What Fruit Is Bigger Than A Watermelon

Richard E. Blackwelder. (1963). Group of the animal KINGDOM 

Teresa Adell et al. (2015). Platyhelminthes. 

Thomas Jankowski and Boris Anokhin. (2019). Phylum Cnidaria.