Animal Kingdom Animalia Subphylum - An Overview
Animals are generally classified into invertebrates and vertebrates. Invertebrates are organisms without a backbone, and include organisms like sponges, worms, insects, and molluscs. The vertebrates have a backbone and include fish, amphibians, reptiles, birds, and mammals. The vertebrates have a well-developed skeletal system and organ systems.
This Story also Contains
- Kingdom Animalia: Historical Context
- General Characteristics of the Kingdom Animalia
- Characteristics of Organisms in the Animal Kingdom
- Significance of the Animal Kingdom
- Recommended Video On Animal Kingdom Subphylum
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Understanding the Animal Kingdom helps us to appreciate how different animals adapt, survive, and interact within the environment. The classification is important in biology and useful in fields such as medicine, agriculture and conservation. The animal kingdom is one of the most important topics in biology.
Kingdom Animalia: Historical Context
Kingdom Animalia consists of multicellular, heterotrophic, and eukaryotic organisms. They obtain food from autotrophs (plants) and other animals and nutrition by ingesting plant or animal material.
However, the classification of the kingdom was not an easy task for the scientist. Several changes took place till the final classification came into existence. Some of the historical context regarding animal classification is mentioned below in the table.
Scientist and Year | Classification System | Key Features |
Aristotle (384-322 BC) | Two Kingdom Classification
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Linnaeus (1707-1778) |
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Ernst Haeckel (1866) | Three Kingdoms |
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Copeland ( 1956) | Four kingdoms classification
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Whittaker (1969) | Five Kingdoms classification |
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General Characteristics of the Kingdom Animalia
All the organisms present in the kingdom Animalia have their specific characteristics. But the overall Kingdom also has some common characteristics which make it fall into this category. Some of the common characteristics of the kingdom Animalia are discussed below:
One of the largest kingdoms with more than 8.7 million species.
The animal kingdom has different levels of organisms like such as heterotrophic organisms in the same category.
Most of the organisms in the animal kingdom have sexual reproduction as their primary mode of reproduction.
The cells lack outer cell walls like plants, but some of them also have cell walls present in them.
Some of the organisms in the animal kingdom are sensitive to external stimuli.
Most of the animals are diploid, which means there are two copies of each gene present.
Characteristics of Organisms in the Animal Kingdom
Apart from the common characteristics, each of the organisms possesses their characteristics. To characterise them in a better way, they are divided into different phyla, which are discussed below along with their key features.
Phylum | Common Name | Body Structure | Symmetry | Reproductive Mode | Examples |
Sponges | Porous body structure with a heart outer skeleton. Non-motile | Asymmetrical | Both asexual and sexual | Sycon and Spongilla | |
| Ctenophora | Comb jellies | Soft, transparent, bioluminescent body with eight ciliated "comb plates" for locomotion | Biradial symmetry | Sexual reproduction, external fertilisation | Pleurobrachia, Ctenoplana |
Coelenterates | Presence of hollow body cavity with outer and inner linings. | Radial symmetry | Sexual and asexual | Hydra, jellyfish and corals | |
Flatworms | Flatten body structure with no internal cavity. | Bilateral symmetry | Sexual and asexual | Tapeworms and Planaria | |
Roundworms | Cylindrical body structure with pseudo cavity | Bilateral symmetry | Mostly sexual | Ascaris and Wuchereria | |
Segmented Worms | Segmented body with cylindrical structure. Presence of true body cavity. | Bilateral symmetry | Sexual and asexual | Earthworms and leeches | |
Arthropods | Segmented body with jointed appendages, presence of an exoskeleton. | Bilateral symmetry | Mostly sexual | Mosquito spiders and butterflies | |
Molluscs | Segmented body with fewer segments and the presence of well-developed organs. | Bilateral symmetry | Sexual and asexual | Snails and octopus | |
Echinoderms | The presence of hard skeletal structures that are made of calcium carbonate. | Radial symmetry | Sexual and asexual | Sea Urchins and Starfish | |
Hemichordates | Soft body structure with a single layer of epidermis. | Bilateral symmetry | Sexual, external fertilisation | Sea Mammals | |
Chordates | Bilateral symmetry with notochord present at the same stage. | Bilateral symmetry | Sexual | Urochordates and vertebrates |
Significance of the Animal Kingdom
The animal kingdom has a great diversity of species, which contributes to maintaining the ecological balance of life on Earth. It is also important to ensure that all the biological processes are functioning effectively. Some of the major points regarding the significance of the animal kingdom are discussed below:
Animals in the animal kingdom are integral parts of the ecosystem and have their roles, such as herbivores, carnivores and omnivores, which regulate the entire population dynamics.
Maintains the energy flow between all the ecosystems.
Biodiversity within the animal kingdom is also responsible for several ecological processes, such as nutrient cycling, decomposition and habitat formation.
Many animals, such as birds, insects and mammals, are also part of the very important process of pollination and seed dispersal.
Decomposers are also part of the animal kingdom, which play an important role in decomposition and nutrient recycling back into the soil.
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| Coelom | Class Chondrichthyes |
| Digestive System of Earthworms | Reproductive System of the Earthworm |
| Vermicomposting | Osteichthyes |
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Frequently Asked Questions (FAQs)
Phylum Chordata possesses a closed circulatory system, while all others have open circulatory systems.
No. Chordates are divided into Urochordata, Cephalochordata, and Vertebrata, depending on the presence of the notochord and vertebral column. Vertebrates have a notochord during the embryonic stage and are replaced by the vertebral column in adults. Both Urochordata and Cephalochordata have notochords only.
Kingdom Animalia is divided into ten phyla, as listed below.
Porifera
Cnidaria
Platyhelminthes
Nematoda
Annelida
Arthropoda
Mollusca
Echinodermata
Hemichordata
Chordata
These animals are multicellular and heterotrophic (depend on other organisms for food). They lack an external cell wall and reproduce sexually. There are about 8.7 million species, of which only a small number are identified and classified. Some animals have a larvae (early) stage before adult life.
Earthworm belongs to the phylum Annelida. These are the segmented ringworms having a cylindrical body. They have a true coelom (body cavity), and the body is differentiated into head and tail. Annelids have a triploblastic structure with bilateral symmetry and are found in the land, freshwater, and marine waters. Leeches are another example of Annelids.
Robert Harding Whittaker gave the five kingdom classifications of organisms. These five kingdoms are named Monera, Protista, Fungi, Plantae, and Animalia.