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. In this article, let us learn how animals are classified under different phyla based on their special characteristics. Now, let us scroll down to know more about the Kingdom Animalia.
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.
Basis of Classification
Animals are classified based on certain common fundamental features. They are given below:
Level of Organization
Depending on the organization 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 organization).
i. Cellular Level – In this, cells are not organized 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 specialized 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.
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.
These are the groups of cells behaving as a unit during the early stages of embryonic development. On the basis of 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 a number of pseudo segments that are independent of each other,
ii. Metameric Linear repetition of body parts.
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:
The members of this phylum are commonly known as sponges. These are pore bearing animals and exhibit the following general characters:
1. These poriferans are the most primitive multicellular animals that show a cellular level of organization.
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 characters:
1. These are multicellular animals with a tissue grade organization and show radial symmetry.
2. These are sedentary s or free-swimming animal 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 metagenesis (alternation of generation) and reproduction occurs by both sexual and asexual methods.
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 organization.
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.
The members of this phylum are commonly known as flatworms because of their dorso-ventrally flattened body. They exhibit the following general characteristics:
1. They are the first animals to have bilateral symmetry and to undergo cephalisation. They are triploblastic animals and show organ system organization.
2. They are free-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 specialized cells called flame cells.
5. These are mostly hermaphrodite and exhibit high power of regeneration.
The members of this phylum are commonly known as roundworms. They exhibit the following characteristics:
1. They are free-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.
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 organization.
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.
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 organization.
3. Excretory organs are represented by coxal glands and Malpighian tubules.
4. These animals are generally oviparous or ovoviviparous.
It is the second-largest phylum in the animal kingdom and is commonly known as soft-bodied animals 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 the quality of water.
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 hermaphrodite.
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.
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, excretion is by glomerulus of the proboscis.
3. They mainly reproduce by sexual reproduction.
Animals belonging to phylum–Chordata is 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
Porifera: Examples involve Sycon, Spongilla, Hyalonema, etc.
Coelenterata: Examples involve Hydra, Aurelia, Physalia, etc.
Ctenophora: Examples involve Pleurobrachia, Velamen, etc.
Fig: Comb jelly
Platyhelminthes: Examples involve Taenia solium, Echinococcus granulosus,etc.
Aschelminthes: Examples involve Ascaris lumbricoides, Wuchereria bancrofti, etc.
Fig: Ascaris lumbricoides
Annelida: Examples involve Nereis, leech, earthworm, etc.
Arthropoda: Examples involve Cockroach, lobster, honey bee, prawn, etc.
Mollusca: Examples involve Pila, Ostrea, Solen, Doris, etc.
Echinodermata: Examples involve Starfish, Sea urchin, etc.
Hemichordata: Examples involve Balanoglossus, Saccoglossus, etc.
Chordata: Examples involve lamprey, lancelets, dog, human etc.
Economic Importance of Kingdom Animalia
Some of the economic importance of the phyla of the kingdom Animalia are given below:
- Phylum Porifera: They are used commercially for bathing or cleaning sponges.
- Phylum Coelenterata: They take part in the formation of coral reefs, e.g., Millipore. They also have an ornamental value (star coral).
- Phylum Ctenophora: They reproduce quickly and are good predators.
- Phylum Platyhelminthes: Fasciola causes fascioliasis or liver rot which is characterised by hepatitis.
- Phylum Aschelminthes: Ascaris causes ascariasis in humans.
- Phylum Annelida: Earthworms are used as fish-baits and for improving soil fertility.
- Phylum Arthropoda: Honeybee produces wax and honey. Prawn and lobster are used as food in many countries.
- Phylum Mollusca: Molluscans like oyster, squid and cuttlefish are used as food in many countries. Sepia ink has medicinal value.
- Phylum Echinodermata: Eggs of sea urchin are used for embryological studies. Sea cucumber is used as food in many countries.
- Phylum Hemichordata: They show affinities with echinoderms, annelids and chordates.
- 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.
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.
Frequently Asked Questions (FAQs) on Kingdom Animalia
Q.1. What does Kingdom Animalia consist of?
Ans: The Kingdom Animalia consists of multicellular eukaryotic organisms that are heterotrophic in nature.
Q.2. What are the two classifications of the animal kingdom?
Ans: The two classification of the animal kingdom are vertebrates and invertebrates.
Q.3. What are the \(9\) major phyla of Kingdom Animalia?
Ans: The \(9\) major phyla of Kingdom Animalia are Porifera, Coelenterata, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Chordata.
Q.4. What are the 4 characteristics of Kingdom Animalia?
Ans: 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., depend on other organisms for food.
c. Most ingest food and digest it in an internal cavity.
d. They do not possess a cell wall.
Q.5. What are the \(5\) animal kingdoms?
Ans: The \(5\) animal kingdoms are the Pisces, Aves, Mammalia, Reptilia and Amphibia.
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