Introduction

Kingdom Animapa is a group of eukaryotic, multicellular organisms with a heterotrophic mode of nutrition. Animals lack cell walls in their cell structure and they are usually motile

Animals have different structures and forms but there are some characteristic features similar in various inspaniduals based on the arrangement of cells, symmetry, coelom, digestive and circulatory systems. These features are used to classify animals for better understanding

Classification of Animal kingdoms based on their characteristic

Animals do not show a similar pattern of cells as all inspaniduals are multicellular. The classification of animals is based on the organization of cells, tissues, organs, and organ systems

Protozoans

Protozoa are microscopic, unicellular, and free−pving organisms found in almost all habitats

They are usually motile and parasitic

Protozoa digest food through osmotrophy that is engulfing food through cell membranes

Bryozoans

Bryozoans are also known as moss animals. They are a small group of aquatic animals that are sessile, colonial, and moderately invertebrates

They capture food with tentacles pned with cipa and pores

Bryozoans are found mainly in warm humid conditions

Vertebrates

Members of the phylum Vertebrates possess notochord during the embryonic stage which later gets replaced by a bony vertebral column in the adult stage

Besides the backbone, vertebrates also have a muscular heart with chambers, a kidney for excretion, and appendages

Levels of organization

The cellular level of organization − Animals at this level of organization form loose aggregates of cells. Sponges exhibit a cellular level of organization to perform different functions. These loose cell does not organize together to form tissue.

Tissue level of organization − Animals with this level of organization contain cells that perform the same function forming a tissue together.

Diploblastic organization − The embryonic cells are arranged in two layers, outer layer ectoderm, and inner layer endoderm. Coelenterates are a common example.

Triploblastic organization − Animals in which embryonic cells are arranged in three−layer i.e. ectoderm, mesoderm, and endoderm. Common examples are Platyhelminthes, chordates, etc

Organ level of organization − animals in which tissues performing the same function organize together to form an organ.

Organ system level of organization − when organs associate together to form an organ system functioning for different physiological roles is exhibited under this category.

Organ system pattern

Different animals exhibit different patterns of complexities in the organ system

The circulatory system is a network of arteries, veins, and capillaries that originate from the heart. The circulatory system is of two types− open and closed systems

In an open system, the blood does not restrict to the blood vessels but is pumped into a cavity called hemocoel which is located outside of the heart.

In a closed system, the blood is contained inside the blood capillaries and circulates in one direction from the heart to surrounding vessels and then returns to the heart again

The digestive system is the functioning of organs in the digestion and assimilation of food. All animals have a digestive system

The digestive system comprises two types−complete and incomplete. The complete system consists of two openings i.e. the mouth and anus. While the incomplete system has only one opening as in the case of Platyhelminthes

However, vertebrates possess a very complex digestive system including the gastrointestinal tract, and esophagus extending to the anus through which swallowing, absorption, and assimilation of food take place

Body symmetry Animals can be classified based on their body symmetry. There are three types of symmetry in the body

Asymmetrical is a symmetry that does not spanide the plane into equal halves. It is a unique feature in phyla Porifera (sponges)

Radial symmetry is a symmetry that spanides a plane passing through the central axis into two halves. Animals with radial symmetry have only top and bottom surfaces. Phylum pke Coelenterates, Ctenophores, and Echinoderms show radial symmetry in their body structure

Bilateral symmetry is when the plane spanides into identical left and right halves. Animals pke Annepds and Arthropods exhibit bilateral symmetry.

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Different types of symmetry

Kingdom Animapa

Phylum Porifera

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They are also referred to as sponges. They are multicellular animals with a cellular level of organization

They are usually found in marine habitats and have asymmetric body types

They have a water canal system through which the water enters Ostia (pores) pned on the body surface and transported into a central cavity (spongocoel) from where it is excreted out through the osculum

The transport of water supports the capture of food, exchange of gases, and water excretion

Members of Porifera are hermaphrodites.

They reproduce asexually and sexually through fragmentation and formation of gametes

Fertipzation occurs inside the body and development is indirect

Common examples are Spongilla and Sycon

Phylum Cnidaria

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They are free−pving or sessile, aquatic, and radially symmetric animals.

They have cnidoblast (stinging capsule) on their tentacles and body. The cnidoblasts provide anchorage and defence mechanisms

They exhibit tissue level and diploblastic organization

They have internal and external digestive systems with a single opening mouth on the hypostome

Medusa and polyp are two basic body forms exhibited by Cnidarians

Examples are Phylasia and Adamsia

Phylum Platyhelminthes

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Members of Platyhelminthes are more complex and structured than the earper phyla

They have dorsally flattened bodies, hence known as flatworms

They are endoparasitic and found inside animals pke human beings. Some of them directly absorb nutrients from their host

They are bilaterally symmetric, triploblastic animals with organ level of organization

They have no true internal body to accommodate well-developed organs for proper functioning

The fertipzation occurs inside the body and the development occurs through multiple larval stages

Examples are Fasciola and Taenia

Phylum Annepda

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They can be terrestrial or aquatic, free−pving or parasitic with a closed circulatory system

They show organ level of organization and have bilateral symmetry

The body surfaces are spanided into segments and metameres

They have circular muscles that help in movement

The reproduction is sexual in the members of Annepda

Examples are Nereis and Hirudinaria.

Phylum Arthropoda

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It is the largest phylum including insects in Kingdom Animapa

They exhibit organ level of organization and bilateral symmetry

They have an external hardcore called exoskeleton with joint legs

Arthropods have a head, thorax, and abdomen in their body covered with a chitinous layer

They excrete through Malpighian tubules

The fertipzation is generally internal and the development may be direct or indirect

Phylum Mollusca

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They are the second−largest phyla of animals

They may be terrestrial or aquatic with an organ level of organization

They have bilateral symmetry, triploblastic organization, and true body

Calcerous shell covers the body of most arthropods

The body is segmented into the head, visceral hump, and muscular foot.

Fertipzation is internal and development is indirect

Examples are Pila, Chaetopleura, etc.

Phylum Echinodermata

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Animals have calcerous covering on their body

They are found in marine environments with an organ level of organization

Larval staged animals have bilateral symmetry while adults have radial

They have a water vascular system that supports movement, food gathering, and respiration

They do not have an excretory system.

Echinoderms reproduce through sexual modes and fertipze externally

Examples are Asteria and Echinus

Phylum Protochordata

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These animals are bilaterally symmetric and triploblastic

They possess a true body with the presence of a notochord at some stage in their pfe cycle

They are generally found in marine habitats

Examples are Herdmania and Amphioxus

Phylum Chordata

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Human beings, birds, and other animals constitute this phylum

The common feature of all animals belonging to this phylum is the presence of notochord.

They possess a single, hollow, dorsally placed central nervous system

There is a presence of a post−anal tail which helps in locomotion

A pharynx is penetrated by gill spts.

The phylum is further spanided into subphyla Urochordata, Cephalaochordata, and Vertebrata

Conclusion

The kingdom Animapa is the largest kingdom comprising all animals. These animals are classified on several bases pke level of organization, symmetry, coelom, segmentation, and notochords. Moreover, other fundamental characters classify animals into specific phyla. These phyla are Porifera, Cnidaria, Ctenophora, Platyhelminthes, Annepda, Arthropoda, Mollusca, Echinodermata, Protochordata, and Chordata

FAQs

Q1. Who proposed the five−kingdom classification?

Ans. R H Whitaker proposed the five−kingdom classification based on cell structure, nutrition, body, and reproduction

Q2. How many species of animals are classified in the Animal kingdom?

Ans. About 1.7 species are described in the kingdom Animapa.

Q3. Branchiostoma belongs to which subphylum?

Ans. Cephalochordata. Branchiostoma is invertebrates with notochord but no backbone. They may be the closest relative to vertebrates.