Classification of Plants and Animal

In this article, we will describe the basic classification of the animal kingdom. This article helps to prepare your study notes for competitive exams such as SSC, PSC and Railway.

Animal Kingdom:

The Animal kingdom is also referred to as Kingdom Animalia. The Animal Kingdom is eukaryotic, and multicellular and contains a million species of animals. Each animal has its own specific features and qualities. They consumed their energy either by feeding on crops or on other mammals. There are millions of species that have been identified, few animals show similarities or common traits while others differ drastically.
Cell walls are absent in animal cells. The most crucial trait i.e. they cannot produce their own food because they have a heterotrophic mode of nutrition. They often digest their food inner side of internal chambers, another characteristic that sets them apart from algae and plants. Except throughout specific life phases, these animals’ motility is another exceptional trait.

Classification of Animal Kingdom:

Animals are classified based on their feature, and structures such as the Arrangement of cells, Body Symmetry, Symmetry and Nature of Coelom, mode of nutrition, and reproduction. Apart from the primary differentiating features of the Animal Kingdom are Eukaryotic, Multicellular, without a cell wall and heterotrophic, etc.

1. Porifera (Pore Bearers):

Porifera is a phylum of aquatic invertebrate animals that comprises sponges. The simplest multicellular aquatic animal is exclusively present in the sea but they are members of the Spongillidae family and live in freshwater. Porifera phylum food intake, gaseous exchange, and excretion occur by the water transport system.  Water enters through the pores referred to as Ostia and goes out through the osculum via a central cavity called a spongocoel. Spongocoel is a hollow tube found in their body. The Porifera phylum body structure is made up of spongin fibers or spicules. The Canal system, which consists of Ostia and canals, is specific to this species. Their body’s water circulation is visible.
Examples: Spongilla, Euspongia, Sycon, Scypha, etc.

2. Coelenterata Cnidaria (Sac-like Animals):

Cnidaria phylum is an aquatic invertebrate animal that comprises the coelenterates. It is usually present in marine environments and attached to the rocks at the bottom of the ocean. Coelenterates are known as the simplest animal group and tissue level of organization, covering large and radially symmetrical or acoelomates. Digestion takes place in the coelenteron, a gastrovascular cavity formed by two-layered walls of the body i.e. epidermis and gastrodermis. The central gastro-vascular cavity has a single opening known as the hypostome, which is covered with sensory plexus.
Examples: Hydra, Obelia, Aurelia (Jellyfish), Pennatula (Sea pen), Corallium (Red coral), physalis, Millipore (Coral), Metridium (Sea anemone), etc.

3. Platyhelminthes (Flatworms):

Platyhelminthes is a phylum a group of soft-bodied bilaterally symmetrical usually flattened invertebrates animals. Apart from that, there are approximately 20,000 species of these phyla. An incomplete digestive system is found in them with no circulatory, respiratory, or skeletons. Internal fertilization and indirect development through many larval stages. Planaria can reproduce. 

Examples: Fasciola, Taenia.

4. Aschelminthes (Roundworms):

Aschelminthes are invertebrate animals that are part of a group of species distinguished by a well-developed coelom and lack of blood vessels. It can be free-living or parasitic. Free-living organisms are quite prevalent in soil and sediment and they feed on bacteria. Internal fertilization occurs with both direct and indirect development in Aschelminthes animals. The majority are tiny wormlike creatures, such as nematodes, rotifers, and water bears
Examples: Ancylostoma, Ascaris, Wuchereria, etc.

5. Annelida (Segmented):

Annelida is a large phylum known as ringworms and segmented worms, which include earthworms, lugworms, ragworms, and leeches. They can be present in different variety of environments including marine waters, fresh waters, and also in moist terrestrial areas. The size of the annelids can range from a few millimeters to an impressive three meters in length. Hemoglobin is absent in RBC while it is absorbed in plasma. A closed circulatory system is present and nephridia act as an excretory organ in the Annelida phylum. Regeneration frequently occurs.

Example: Earthworms, Lugworms, Ragworms.

6. Arthropoda:

Arthropoda are a large group of invertebrate animals that comprises insects, spiders, crustaceans, and other members of their family. These phylum animals have a segmented body, an external skeleton, and jointed limbs. The largest number of species around 17000 species belong to this phylum. The body shape is categorized into the Bilaterally symmetrical, triploblastic, and metamerically segmented body. The body structure is divided into three parts which are the head, thorax, and abdomen. A cephalo-thorax is a common combination of the head and thorax. The exoskeleton, which is formed from the cuticle, is present. The body cavity is hemocoel i.e. filled with blood. the open circulatory system is present in the Arthropoda phylum animals. Excretory organs are green glands, coxal glands, or Malpighian tubules.

Symmetrical: This means that it is divided body structure into two identical parts. 

8. Mollusca:

Animals belonging to the phylum Mollusca have generally soft bodies that are surrounded by a hard exoskeleton and their body shape is categorized as triploblastic and bilaterally symmetrical, and coelomate. They can be present in terrestrial areas and the depths of the seas. The molluscans’ sizes can range from 20 meters to one millimeter, and they even include some microscopic species. These animals continue to have a crucial role in the lives of humans. Molluscans have one or two calcareous (calciferous) shells. Respiration occurs in the Gills or pulmonary chambers. The fertilization can occur for both direct or indirect processes with three larval stages i.e. trochophore, veliger, glochidium, etc.
Examples: Octopus (Devilfish), Dentalium (Tusk shells), Doris (Sea Lemon), Pila (Apple Snail), etc.

9. Echinodermata:

Echinoderms are marine animals and can be present in the depths of the ocean as well as in the aquatic environment. The body shape is categorized as fivefold radial symmetry, a calcareous skeleton, and tube feet operated by fluid pressure. Echinoderms are especially marine animals and triploblastic and coelomate in nature. A water vascular system is present in the Echinoderms phyla. Due to external fertilization, echinoderms are sexually dimorphic and discharge their sperm and eggs into the sea. The neurological system is a relatively simple structure in these phyla with a nerve ring at the center and five radial nerves extending outward along the arms. Regeneration power is well developed. They are also called spiny-skinned animals.
Examples: Starfish, sea cucumber, brittle star, sea urchins, etc.

10. Chordata:

Chordata is the third largest phylum of the animal kingdom that involved all the vertebrates each together with the sea squirts and lancelets. The existence of a notochord differentiates them under certain conditions during their development.
The organisms of this phylum have four traits throughout the following stages of their life, the stages are mentioned below.

• Nerve cord Notochord – The notochord is a cartilage longitudinal rod that runs between the nerve cord and the digestive tract. Its perform major role to support the nerve cord.
• Dorsal Tubular Nerve Cord – This is a bundle of nerve fibers that connects the brain to the muscles and other organs.
• Pharyngeal Slits – Pharyngeal slits are a third chordate feature and These are the openings between the pharynx or throat and the outside. In primitive bacteria, these membranes filter food particles from water. These pores allow water to enter through the mouth, without entering the digestive tract.