What will you learn? show

This blog will briefly explore the Kingdom Animalia, its classification. And introduce all phylum, namely Protists, coelenterate, Ctenophora, Platyhelminthes, aschelminthes, Annelida, Arthropoda, Mollusca, and Echinoderm, Hemichordate, and Chordata.

this image will provide the Roadmap for the better understanding of the blog and all phylum, namely Protists, coelenterate, Ctenophora, Platyhelminthes, aschelminthes, Annelida, Arthropoda, Mollusca, and Echinoderm, Hemichordate, and Chordata of Kingdom Animalia — **Roadmap for the better understanding of the blog**

At a Glance

In the earlier blogs, we have studied living world diversity. Accordingly, all the living creatures in nature get divided into various classes, family, order, phylum, species, genus, and kingdoms. This classification is based on multiple factors; similarly, animals also get classified into different categories accordingly. Some basic questions about animals’ classification must raise in our mind like,

How all the animals get classified?
Why the animals get recognition from the different categories? And the most basic question
How all these animals get summaries under one Kingdom?

All Multicellular living organisms do not possess the same pattern. Similarly, all members of Kingdom Animalia are multicellular still do not show similarity in their internal body arrangements. Every animal has its own different identity. Various individuals offer some common features despite structural differences and their different forms. These common features include an arrangement of cells, pattern of the digestive system, respiratory system, body symmetry, nature of coelom, and reproductive system. These are some fundamental features that are used for animal classification. And that is why we can differentiate between dogs, butterflies, and worms.

Let’s take a simple example of dog, fish, and worm. As we know, the dog has four legs so that he could run and walk on roads. Similarly, fish has wings and gills, which are useful for survival underwater. And worm can live in water and on-road though it does not possess legs, wings, gills, etc. These are some basic and common features different animals possess. And that is why every individual is different from the other.

Organization level in Kingdom Animalia

As we know, different cells combine to form tissue, a group of tissues combines to form organs, and various organs combine to create an organ system. In the same way, animals also show different body organization levels, namely.

The cellular level of organization – the animals in which cells are arranged loosely aggregate form-shows some activities among cells—for example- sponges.
Tissue level of organization – a group of cells performing the same function is combined to form tissue. For example- coelenterates.
Organ level of organization – in this level, tissue groups together to form an organ. And different organs combine to form an organ system that is concerned with a specific physiological function—for example- annelids, arthropods, etc.

The organ system is different in every group of animals. To illustrate, usually, the digestive system comprises one mouth for food entry and one anus for the waste exit. In contrast to that, Platyhelminthes has a single opening outside the body, which works as mouth and anus. Similarly, some animals show the open type of circulatory system in which cells directly bathe into the blood pumped out of the heart. On the other hand, blood is circulating through vessels, veins, and capillaries in the closed type of circulatory system.

this diagram will explain the Levels Organization in Kingdom Animalia — Levels Organization in Kingdom Animalia

Classification of the animals is not ended here. It is considered as starting for the classification of the animals. Accordingly, animals further get classified into more detailed categories based on their features.

Categorization of animals under Kingdom Animalia

Animals classification based on their symmetry, the number of layers present on the Embryo, segmentation, presence of the notochord, and presence of coelom.

Classification in Kingdom Animalia based on symmetry

Based on symmetry, animals get divided into three categories, namely,

Asymmetrical– in this type, animals get divided into two unequal parts if the line is passed through their line of symmetry. For example, suppose you cut singhara or water chestnut from the line of symmetry. In that case, you will never get equal pieces because of their irregular shape, like in sponges.

Radial symmetry – in which animals get divided into two equal parts. If you cut a tree vertically from the line of its symmetry tree will get cut into two equal parts. Still, the number of branches and leaves is different on both sides, radially symmetrical cut—for example, echinoderms.

this diagram will explain the detail of body symmetry in Kingdom Animalia — **Body Symmetry**

Bilateral symmetry – in this type, animals get divided into two equal right and left halves. If you cut the human body from the line of symmetry, you will get two equal right and left parts as both sides possess an equal number of hands, legs, eyes, etc.

Classification in Kingdom Animalia based on Embryo

in this category, differentiation of animals is done based on the organization of the Developing Embryo. Skin is made up of three essential layers innermost Endoderm, middle one Mesoderm, and outermost Ectoderm. You can imagine it like three bangles place within each other in decreasing size. And these layers’ formation starts as embryo development starts. When two layers, namely ectoderm and endoderm, among the three layers, are present with undifferentiated layer mesoglea within is known as Diploblastic. And when all the three layers present on the Embryo is known as Triploblastic.

Classification in Kingdom Animalia based on coelom

The most important feature of animal classification is the presence of coelom. The coelom is the cavity present between the body wall and gut wall, and it is found in the mesoderm. The presence of coelom divide animals into three subcategories, namely.

Coelomate is the organism in which coelom is present, such as insects, arthropods, etc.
Pseudocoelomate – animal body in which cavity is not lined with mesoderm, instead of that mesoderm, is present in the scattered pouches between ectoderm and endoderm. For example, in Aschelminthes.
Acoelomate – the animal body in which the body cavity is not present. For example, Platyhelminthes.

Classification in Kingdom Animalia based on segmentation and notochord

Animals get divided into segmented ones and non-segmented ones. If the animal body is divided or marked into small ring-like or box-like marking internally and externally, it is a segmented body. For example, earthworms it is well known for metameric segmentation.

The notochord is a rod-like structure derived from mesoderm, formed on the dorsal side of the animal body during embryonic development in some animals. Animal with notochord is known as chordates, and without notochord are non-chordates.

Phylum’s of The Kingdom Animalia

As we know, different phylum combine to form a kingdom. Kingdom Animalia also includes many phyla in it. Following is a brief introduction about the phylum under Kingdom Animalia.

PHYLUM PORIFERA

Porifera meaning the “pore bearer,” means species that bears tiny hole structure called pores on its surface. These pores are work for water transport as a canal system. You must have heard about the famous cartoon “SpongeBob SquarePants” that SpongeBob belongs to this Porifera phylum. It includes sponges which are primarily marine individuals. These are asymmetrical multicellular organisms with a cellular body organization. The pore is called Ostia, through which water transport to the central cavity, came out via spongocoel. Ostia and spongocoel help in the gathering of food, removal of waste, and also respiratory exchange. The digestion method is intracellular. These species are hermaphrodites, which means the same individual produces sperm and egg.

PHYLUM COELENTERATE / CNIDARIA

The word coelenterate is derived from the ancient Greek word koilos means hollow, and enteron means intestine. These are the aquatic, mostly marine individuals who are freely swinging and motile.

These species possess radial symmetry with tissue-level organization and diploblastic. The Central gastrovascular cavity with a single opening mouth is present in these Species. In this type, two bodies are form namely polyp, which is in a sessile and cylindrical shape, and medusa, an umbrella-shaped and free-swimming body like jellyfish. It presents in both forms and shows alteration of the generation that is metagenesis. It means polyps produce medusa asexually, and medusa produces polyps sexually—for example, sea fan, sea pen, etc.

PHYLUM CTENOPHORA

It looks like jelly is associated with a comb-like ciliated structure. Hence, comb jelly or sea walnuts are derived from the Greek word ctene or comb and phora or bearer. These are the radially symmetrical, diploblastic, exclusively marine organism with the tissue-level organization. Organism shows external and internal digestion. The sexes are not separated in these species, although it shows only sexual reproduction. These species have the unique property of bioluminescence that is a remarkable ability of living organisms to emit light—for example, ctenoplana, Pleurobrachia.

PHYLUM PLATYHELMINTHES

The word is derived from the Greek word platy means flat, and helminths mean worms. According to their name, these species have dorsoventrally flattened body hence call flatworms. These species present as endoparasites in animals and humans, and parasitic forms can be hooks or suckers. These are bilaterally symmetrical, with the organ-level organization. The specialized cell called flame cells is present in these species, which helps in the osmoregulation and the excretion. Flatworms are Triploblastic, acoelomate animals. Sexes are not separated in this species, and it shows internal fertilization and development through many larval stages. One of its examples, planaria, has a higher regeneration capacity. Even a small piece of this organism can develop into a complete organism.

PHYLUM ASCHELMINTHES

The name is derived from the ancient belief of animals of these group has fluid-filled internal sacs. Askos means sac, and hence these circular body organisms are named roundworms. Aschelminthes are free-living, aquatic, terrestrial, or parasitic animals. Roundworms show bilateral symmetry with an organ system. And triploblastic, pseudocoelomate body. Sexes are separated that is dioecious and female is longer while males are shorter in length. It shows internal fertilization with indirect or direct development—for example, roundworm, filaria worm, hookworm, etc.

PHYLUM ANNELIDA

In Latin, annulus means small ring. These animals are aquatic as well as terrestrial free-living and sometimes parasitic. These animals are triploblastic, with bilateral symmetry. And metamerically segmented, coelomate body with the organ-level organization.

Insects animals possess longitudinal and circular muscles for locomotion. These animals are separately classified because of their special ring-like body marks, dividing them into segments or metamers. These animals possess a closed circulatory system but do not possess a respiratory system—for example, nereis, earthworms, etc.

PHYLUM ARTHROPODA

Around two-thirds of all species on earth are Arthropods. Arthropoda is the largest phylum include insects. Arthos means joint, and podas means appendages. It includes organisms with organ system-level organization, bilateral symmetry. And triploblastic, segmented coelomate body. Animals under this phylum have chitinous exoskeleton cover on their body.

These animals possess joint appendages like the head, thorax, abdomen, etc. Arthropods also include respiratory organs, for example, lungs or tracheal system, gills, etc. And possess an open circulatory system, some sensory organs like antennae, eyes, some balancing organs. Arthropods have Malpighian tubules for excretion. Insects are dioecious, oviparous. And show internal fertilization with direct and indirect development. Some examples of economically important arthropods are honey bees, silkworms, etc.

PHYLUM MOLLUSCA

According to the Latin translation, Mollusca means soft. These animals are terrestrial or aquatic. It is the second-largest phylum after Arthropoda.

Mollusca has a bilaterally symmetrical, triploblastic, and coelomate body. And organ system level organization. The body of Mollusca is covered with the calcareous shell, which is mainly made up of calcium carbonate, and it supports and protects the soft and fleshy parts of Mollusca. The body is unsegmented with a separate head, muscular fast, and visceral hump. Fast is a type of twitch muscle that helps in sprinting and jumping.

On the other hand, the visceral hump holds all the internal systems of the body together. The soft and spongy layer of skin forms the mantle over the visceral hump. The space between hump and mantle is the mantle cavity. Feather-like gills for respiration and excretory purpose are present in the mantle cavity. Mollusca is dioecious, oviparous with indirect development. Apple snail, octopus are the best examples of Mollusca.

PHYLUM ECHINODERMATA

In the Greek language, Echinos means spiny, and dermos means skin. Because of the presence of spines on the body, these organisms are named Echinodermata. It possesses a calcified ossicle that forms the skeleton of invertebrate animals. These animals are marine and include organ-level organization.

The adult spiny bodies show radial symmetry, while larval stage echinoderms show bilateral symmetry. A complete digestive system with a mouth on the lower side and anus on the upper side is present in echinoderms. Both the sexes of these animals are living without an excretory system. Reproduce sexually with external fertilization and indirect development—for example, sea urchin, star fish, sea lily, etc.

PHYLUM HEMICHORDATE

According to the Greek prefix, Hemi means half, while in Latin, chorda means cord. In the early stage, hemichordates possess a structure similar to the notochord, a flexible hollow tube term as stomochord. In the ancient days, it is a sub-phylum under the phylum Chordata. And later get the identity of a separate phylum. It consists of a small group of worms like marine animals with an organ system. And bilaterally symmetrical, triploblastic, and coelomate bodies. Its cylindrical body structure possesses three main parts, namely proboscis, collar, and long trunk with the open circulatory system. Gills are present for respiration and probosci’s glands for excretion.

PHYLUM CHORDATA

The fundamental feature of the chordates is the presence of a hollow dorsal nerve cord that is notochord and a pair of pharyngeal gills. Animal under Chordata possess a post tail and close circulatory system. These animals have a triploblastic coelomate, bilaterally symmetrical body. Chordates are further divided into three sub-phyla, namely urochordates, cephalochordates, and vertebrates.

This sub-phylum we will discuss in detail in upcoming sessions.

CONNECT WITH US

JION OUR NEWSLETTER FOR THE LATEST UPDATES