Animal Kingdom: Basis Classification
The Animal Kingdom is a vast and diverse group containing species from simple sponges to complex animals. The Animal Kingdom is a group of living things that includes all animals. These are multicellular organisms that cannot make their food (heterotrophic) and depend on other living things for energy. The Classification of the Animal Kingdom is based on the possession of certain key characteristics, such as bilateral body symmetry, notochord, segmentation, and coelom. The Animal Kingdom chapter in Biology deals with the taxonomy of the animal kingdom, grouping animals according to common characteristics and relationships during evolution.
- Basis Of Classification Of Animal Kingdom
- Levels of Organization in Animals: From Cells to Organ Systems
- Types of Body Symmetry in Animals: Asymmetrical, Radial, and Bilateral
- Germ Layers in Animal Development
- Coelom in Animals: Coelomate, Pseudocoelomate, and Acoelomate
- Animal Segmentation: Segmented and Non-Segmented Body Plans
- Notochord in Animals
- Different Phyla of Animal Kingdom
- Recommended video on "Classification Of Animal Kingdom"
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The basis of classification into the animal kingdom helps understand the diversity of animals and their evolutionary relationships. Animals are also grouped by the presence or absence of a notochord, which separates Chordates from Non-Chordates. Animal cells are eukaryotic and do not have rigid cell walls. This article includes the Basis of Classification of the Animal Kingdom, 11 phyla of the kingdom Animalia, and key features like body symmetry, type of organisation level, body cavity, and segmentation. These features help scientists understand how animals are related and how they evolved.
Basis Of Classification Of Animal Kingdom
The Basis of Classification of the Animal Kingdom is a fundamental aspect of biology that organizes animals into hierarchical categories based on shared characteristics and evolutionary relationships.In the animal classification kingdom, organisms are grouped into various phyla, such as Chordata for vertebrates and Arthropoda for invertebrates, to reflect their distinct anatomical and physiological traits. The levels mentioned for the basis of classification of the animal kingdom are as described below:
Level of organization
Body symmetry
Germ layers
Body cavity (coelom)
Segmentation
Presence or absence of notochord
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Levels of Organization in Animals: From Cells to Organ Systems
Every single animal in the animal kingdom is multicellular. However, the degree of cell organisation varies among different animals. Animals can range from basic cell aggregations to complex cell arrangements that give rise to tissues and organs.
Level of Organisation | Description | Examples |
Cellular Level | Animals with loosely organized cells where each cell is responsible for all life functions, including breathing, nutrition, and excretion. | Porifera (e.g., Sponges) |
Tissue Level | Groups of similar cells perform specific functions; certain metabolic activities are carried out by designated tissues, such as those for digestion or respiration. | Coelenterates and Ctenophores |
Organ Level | Groups of tissues that work together to perform specific functions; specialized organs are present for various purposes like respiration, digestion, and excretion. | Platyhelminthes and Aschelminthes |
Organ System Level | More complex arrangements where organs form systems to perform specific physiological functions; each system is dedicated to a particular function. | Arthropods, Echinoderms, Chordates |
Types of Body Symmetry in Animals: Asymmetrical, Radial, and Bilateral
If a figure can be split into two equal halves, it is said to be symmetrical. Animals can have radial symmetry, bilateral symmetry, or asymmetry.
Type of Symmetry | Description | Examples |
Asymmetry | Animals with nearly asymmetrical shapes; no plane can divide the body into two equal parts. | Sponges |
Bilateral Symmetry | Only one plane can divide the body into two identical halves; most animals exhibit this type of symmetry. | Annelids, Arthropods, Molluscs, Echinoderms, Hemichordates, Chordates (note: echinoderms can show bilateral or radial symmetry depending on development stage) |
Radial Symmetry | The body can be divided into identical halves by any plane passing through the central axis; appears circular from any angle. | Coelenterates, Ctenophores, Echinoderms |
Germ Layers in Animal Development
The layers of cells in an embryo are called germinal layers. These layers are known as the germinal layers because they are where many organs originate or germinate. Organs can develop from endoderm, mesoderm, or ectoderm, depending on the kind.
Type | Description | Examples |
Diploblastic | Animals with cells organized into two embryonic layers: ectoderm and endoderm. A non-differentiated layer called mesoglea lies between them. | Coelenterates, Ctenophores |
Triploblastic | Animals with cells organized into three embryonic layers: ectoderm, mesoderm, and endoderm. | Platyhelminthes, Annelids, Arthropods, Chordates |
Coelom in Animals: Coelomate, Pseudocoelomate, and Acoelomate
Different animals may or may not have a coelom or body cavity. Mesoderm lines the coelom. Animals are divided into three groups based on this feature.
Type | Description | Examples |
Coelomates | Animals that possess a true body cavity (coelom) lined by mesoderm. | Molluscs, Arthropods, Chordates |
Pseudocoelomates | Animals with a false cavity (pseudocoelom) that is not lined by mesoderm and have patches of mesoderm. | Aschelminthes |
Acoelomates | Animals that lack a true body cavity (coelom). | Platyhelminthes |
Animal Segmentation: Segmented and Non-Segmented Body Plans
In certain species, the body is segmented both internally and externally, with at least some organs repeated serially. For example, the body of an earthworm has a pattern known as metameric segmentation.
Eg: Phylum Annelida (e.g., earthworms, leeches)
Notochord in Animals
The notochord is a rod-like structure located on the dorsal (back) side of the animal's body. The notochord originates from the embryo's mesoderm and is mesodermally generated. In most animals, the notochord forms during embryonic development and vanishes later. Even in later phases in some species, it could still be rudimentary. Animals are classified as chordates if a notochord is present. Non-Chordate refers to an animal lacking a notochord, such as echinoderms and Porifera. The notochord is a structure seen in hemichordates and chordates.
Different Phyla of Animal Kingdom
The animal kingdom classification system organises living organisms into hierarchical categories, starting from broad groups like kingdoms and phyla down to specific species. In animal kingdom classification, animals are divided into various phyla based on their body structure, reproductive methods, and genetic relationships, with Chordata and Arthropoda being two of the largest groups. Advances in molecular biology have significantly impacted animal kingdom classification, allowing scientists to refine classifications based on genetic data rather than solely on physical traits. They progress from the most basic to the most complex in the chart classifying animals. The animal kingdom is classified into 11 different phyla namely: Porifera, Coelenterata, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata and Chordata. Understanding animal kingdom classification is essential for biologists as it provides a framework for studying the diversity of life and the evolutionary relationships among different species.
Phylum | Common Name | Characteristics | Examples |
Sponges | - Basic multicellular animals - Bodies covered with pores (Ostia) - Canal system for circulation of water and nutrients - Supported by spicules - Minimal tissue differentiation | Spongilla, Sycon | |
Cnidaria | - More body differentiation - Single opening for ingestion and egestion - Diploblastic with two germ layers - Can live solitary or in colonies | Jellyfish, Sea Anemones, Hydra | |
Comb Jellies | - Marine animals - Radially symmetric and diploblastic - Bioluminescent - Eight rows of ciliated comb plates for locomotion | Pleurobrachia, Ctenoplana | |
Flatworms | - Dorsoventrally flattened bodies - Triploblastic with three germ layers - Acoelomates with bilateral symmetry - Presence of flame cells for excretion | Planaria, Liver Fluke, Tapeworm | |
Roundworms | - Triploblastic and bilateral symmetry - Cylindrical body shape - Pseudocoelomates (no true coelom) - Complete alimentary canal | Ascaris, Wucheria | |
Segmented Worms | - Found in various environments (land, freshwater, marine) - Triploblastic and bilaterally symmetrical - True coelomates with segmented bodies | Earthworms, Leeches | |
Jointed-Legged Animals | - Largest phylum in the animal kingdom - Body divided into head, thorax, abdomen - Open circulatory system - Chitinous exoskeleton | Crabs, Spiders, Mosquitoes | |
Molluscs | - Second-largest animal phylum - Coelomate and bilaterally symmetrical - Organ-system level organization - Presence of radula for feeding | Octopus, Snails, Mussels | |
Spiny-Skinned Animals | - Marine animals with calcareous endoskeletons - Triploblastic with a coelomic cavity - Radial symmetry in adults but bilateral in larvae | Starfish, Sea Urchins | |
Acorn Worms | - Marine animals resembling worms - Triploblastic and bilaterally symmetrical - Open circulatory system | Balanoglossus, Saccoglossus | |
Chordates | - Presence of notochord, dorsal hollow nerve cord, paired pharyngeal gill slits - Coelomate with organ-system level organization | Amphioxus (Lancelet), Ascidia (Urochordata) |
The animal classification kingdom has evolved over time, with advancements in genetic research leading to the re-evaluation of certain classifications based on molecular data rather than just physical characteristics.
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Recommended video on "Classification Of Animal Kingdom"
Frequently Asked Questions (FAQs)
The basis of classification of the Animal Kingdom is how animals are built and how their bodies work. Scientists look at:
- Body structure (simple or complex)
- Symmetry (shape of the body)
- Body cavity (space inside the body)
- Germ layers (layers formed in early growth)
- Segmentation (body divided into parts)
- Notochord (a rod-like structure in some animals)
The repeating of similar bodily parts is known as metamerism. Metamerism is also called segmentation. The Annelids, which include earthworms, leeches, and tubeworms exhibit this sort of development. Additionally, Arthropods, which include crustaceans, insects, etc exhibit it in a more developed form.
Pseudocoelom is the characteristic feature of the phylum Aschelminthes.
The characteristic features of all chordates are:
Presence of notochord.
Presence of dorsal nerve cord.
Triploblastic.
Post anal tail is present
Pharyngeal slits are present.
The basis of classification has made it simpler to study animals. Learning about organisms and comparing one set of animals to another for a better understanding are becoming simpler.
The major classifications of the animal kingdom include various phyla, such as Porifera, Coelenterata (Cnidaria), Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata, and Chordata.
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