Animal Kingdom: Basis of Classification
Introduction:
Each animal has its own characteristics or symptoms. Each animal group can be separated by these characteristics. Prioritize these characteristics of the animal body for the purpose of classification. Either is used as the basis of classification. Classification of animals on the basis of which characteristics are predominant. Either of those characteristics is called the basis of classification. The main bases of animal classification are-
(1) Body Size.
(2) Levels of organization.
(3) Cleavage.
(4) Germ layer.
(5) Symmetry.
(6) Polarity.
(7) Body axes and plane.
(8) Metamerism or segmentation.
(9) Coelom.
(10) Tagmatization.
(11) Notochord.
(12) Way of living.
(13) Alimentary canal.
(14) Nutrition.
(15) Appendages.
Below is a summary of some of the main characteristics of animals that can contribute to the basis of classification.
1. Body shape:
Animals are divided into two categories based on size. Namely---
- Micro or microscopic animals: These animals are microscopic and very small. They cannot be seen with the naked eye. Examples:- Plasmodium vivax (malaria bacteria), Entamoeba histolytica (diarrhea bacteria), Loa loa (eye worm), etc.
- Macro or largest animal: These animals are generally large in size and it can be seen with the eyes. Examples:- Duttaphrynus melanostictus, Homo sapiens (human), etc.
2. Levels of organization:
From the point of view of origin and evolution, animal bodies are organized from simple to complex. It is basically a unicellular or non-cellular organism organization where cells are united to form organs, organs, organelles, etc. for the purpose of division of labor on the basis of work. The result is gradually complicated. The body formation process of the animal is completed. Each level of cellular complexity in an organism is called a level of organization. Animals can be divided into several groups based on the degree of cellular organization. namely-
- Cellular grade or level of organization: There are many organisms composed of loosely connected cells that belong to this dimension. There is some division of labor here. But such levels do not result in cell-rich bananas. Example- All animals belonging to the order Porifera.
- Cell-tissue grade or level of organization: In this case, the cells engaged in the same work in the animal body are grouped together to form tissue. Examples: Cnidaria s All animals belonging to the order Ctenophora.
- Tissue-organ grade or level of organization: Organisms that have many types of tissues and the tissues combine to form an organ belong to this level. Examples: – All animals belonging to the order Platyhelminthes.
- Organ-system grade or level of organization: Organs of higher animals combine to form functional systems. Each organ has its own different function. All advanced animals belong to this dimension. Examples: all animals from Nematoda to Chordata.
3. Cleavage:
The method in which the zygote divides continuously in the mitotic process to form numerous offspring cells or embryos is called cleavage. The daughter cell resulting from cleavage is called a blastomere. The first cell division from the zygote results in the formation of a ball-like multicellular sphere. This sphere is called the morula. Then the cells of the morula stage are arranged in a layer and create an embryo called blastula by forming a space called blastocoel inside. The process of cleavage also ends when the transformation into a blastula is completed.
Different types of cleavage are seen in different animals and groups of animals. Because of that in the classification of animals. Cleavage is important. namely-
- Radial cleavage: In this case, the cleavage plane always divides the zygote arbitrarily and symmetrically. All the blastomeres produced are similar in appearance and the aorta are symmetrically arranged. Examples: Cleavage in Arthropoda animals.
- Bilateral cleavage: In this case, till the second division, it is like radial cleavage, but the next division happens transversely along the midline, so that two rows of four cells are formed, and as a result, bilateral symmetry is seen. Examples: Cleavage of Chordata.
- Spiral cleavage: During the third cleavage after the first and second cleavage, the blastomeres of the animal pole (the end of the zygote that contains the nucleus) cycle with the blastomeres of the vegetal pole (the end of the zygote that contains the cytoplasm). By changing the place slightly. Such cleavage is then called rotation or spiral cleavage. Examples: Cleavage in animals of the order Annelida Mollusca.
Figure: Spiral and Radial cleavage.
4. Germ layers:
In zygotes of reproductive multicellular organisms, the morula and blastula divide and cross over to form a two-layered or three-layered gastrula. These cellular layers present in the gastrula stage of the embryo are called the embryo layer or germ layer. Two-layered In other words, the cell layer of the embryo from which various organs and various organs develop in the future (mature animal) is called the germ layer. Embryonic cells are arranged in two or three layers.
Diploblastic animals: Animals whose embryos have two embryonic layers called ectoderm and endoderm. Those animals are called dicotyledonous animals. Between the two layers is the sticky jelly-like acellular mesoglea. Examples: All animals of Cnidaria.
Triploblastic animals: Animals whose embryos have three embryonic layers namely ectoderm, mesoderm, and endoderm are called triploblastic animals. Like- Platyhelminthes, Mollusca, and Annelida, animals of Arthropoda, Echinodermata, and Chordata. Creation of various organs of the animal body from the embryonic stage. Scientist H. C. Pander (1817) discovered three embryonic stages of the animal while observing chicken embryos. The three embryonic stages in the adult animal result in the organs that develop in the adult animal.
- Ectoderm: Epidermis of skin, mouth, anus, layer of nostrils, gum, and white glands, eye lenses, hair, feathers, horns, tooth enamel, ears, nose, nervous system, and brain.
- Mesoderm: Muscle and skeleton, the dermis of the skin, dermal scale and Dentin, excretory System, reproductive System, Additives: Blood and blood vessels, mesentery; the layer of the coelom
- Endoderm: Alimentary canal, trachea,, and secretory part of lungs, liver, pancreas, thyroid, parathyroid, thymus, urinary bladder, and, Urinary tract.
Figure: Ectoderm, Mesoderm, and Endoderm
5. Symmetry:
Symmetry is the balanced distribution of different parts of the animal body in accordance with the axis. In other words, the rule of dividing an organism into equal parts along an axis or plane is called symmetry. Most organisms exhibit symmetry. Below are mainly 5 types of symmetry in animals are observed, namely-
- Spherical symmetry: When a spherical animal body is centered at its. can be divided into equal parts by is called spherical or overall symmetry. For example - Volvox. Radiolaria, Heliozoa, etc. are unicellular protists.
- Bilateral symmetry: When the body of an animal is oriented along its central axis. When it can be divided longitudinally into two equal parts (right and left i.e. sagittal plane) only once, it is called bilateral symmetry. They are placed in the taxonomic category Bilateria. They are three-tiered organisms. , Examples: Platyhelminthes, Nematoda, Annelida Mollusca, Arthropoda (Periplaneta americana), Echinodermata and Chordata (Homo sapiens). Insects are bilaterally symmetrical.
- Radial symmetry: When the body of an animal can be cut at any plane along the central perpendicular axis and divided into more than two equal parts, then that type of symmetry is called radial symmetry. Their taxonomic stage is placed in Radiata. For example, Cnidaria (Hydra, Jellyfish, Sea Anemone, etc.) and most of the animals of Echinodermata. However, tetrameric is found in jellyfish and special pentamerism is seen in animals such as sea stars, sea urchins, sea lilies, etc.
- Biradial symmetry: When an animal has its oral paramount it is called biaxial symmetry. It can be divided equally into two planes along the (oral-aboral) axis. Such symmetry is seen in animals such as Ctenophora and Anthozoa.
- Asymmetry: When an animal's body is cut along the axis or plane of the body into similar equal parts. When it cannot be divided it is called asymmetry. Examples:,- Pila globosa (Apple Snail, Mollusca-Gastropod) Cliona celata (Sponge, Porifera), etc.
Figure: Bilateral(left), and Radial symmetry (Adapted URL: https://www.pmfias.com/classification- animalia-animal-kingdom)
6. Polarity:
The polarity of the animal body based on the position of the head and mouth is called polarity. The names and floors of different areas or aspects of the body are related to this alignment. The end of the animal's head is called the anterior end, and the opposite end is called the posterior end. Again, the end of the animal where the mouth hole is called the oral end, and the opposite end of the mouth is called the aboral end. The surface of the animal's body is called the dorsal part and the bottom is called the ventral part, and the two sides of the body are called the lateral part.
7. Body axes and planes:
Body axes and planes are an important basis of classification in symmetrical animals. In symmetrical animals, a straight line can be imagined along the center of the body, called the body axis. The axis of the body extending from the head to the tail is called the longitudinal axis and the transverse axis of the body is called the transverse axis. Again the body can be anatomically dissected in relation to the body axis. It is called a plane. Alternatively, the region along which the animal body can be divided into right and left or longitudinal and posterior or anterior and posterior regions is called dol. Symmetrical animal bodies can generally be divided into three layers. namely the medial plane, frontal plane, and transverse plane.
- Median or Sagittal plane: This plane divides the body into right or left halves. By sharing it includes the transverse and lateral axis.
- Frontal plane: Any plane with a vertical and a transverse axis. For this reason, it is parallel to the country in the case of bilaterally symmetrical animals.
- Transverse plane: It is any plane at right angles to the transverse axis, it is at right angles to the frontal and sagittal planes.
8. Metamerism or Segmentation:
Metamerism or Segmentation is the linear or longitudinal repetition of body segments called fragmentation or metamerism. Each segment is called a metamere or somite. Animals can have different types of metameres, viz.-
- Homonomous metamere: Animals whose body parts are similar or are of the same type, they are termed homonymous. For example, the dismemberment of earthworms, leeches, etc
- Heteronomous metamere: Animals whose body parts are dissimilar or different types, they are called heterogeneous or heteronomous. For example, the division of insect class (Arshola).
- Asegmental: Such animals have no segmental cells. For example, oysters, Beach, etc. True segmentation refers to animals belonging to the order Annelida (external and internal segmentation) but Arthropoda (external segmentation) and Vertebrates (internal segmentation) also fall under segmentation. But Cestodes show atypical metamerism Go. Importance of segmentation in the evolution of organisms with simple to a complex organization.
9. Coelom:
The space between the alimentary canal and the body wall of the animal body is called the body cavity. A body cavity lined by a membrane of peritoneum arising from the embryonic mesoderm is called the Coelom. Coelom contain animals ranging from Mollusca to Chordata. Animals are classified into the following groups based on the presence, absence, and nature of Coelom.
- Acoelomate: Animals whose bodies do not have coeloms are called acoelomates. During embryonic development, the internal cavity i.e. blastocoel Examplemesodermal spongy parenchyma is filled with cells. In animals, the body cavity is filled with mesenchyme and muscle. Examples: Porifera, Cnidaria, Ctenophora, Platyhelminthes, Nemertea, etc.
- Pseudocoelomate: Animals whose body cavity is not covered by mesodermal peritoneum are called pseudocoelomate or pseudocoelomate. In the embryonic stage, the outside of the blastocoel of these animals is covered by mesodermal cells but in mature animals, the body cavity is not covered by mesodermal peritoneum. A layer of muscle exists around the body cavity. For example - Nematoda, Acanthocephala, Rotifera, Entoprocta, Kinorhyncha. In animals whose body cavity is derived from mesoderm, Not covered by the peritoneum. A layer of muscle exists around the body cavity. For example - Nematoda, Acanthocephala, Rotifera, Entoprocta, and Kinorhyncha.
- True Coelomate or Eucoelomate: Animals whose body cavity is derived from mesoderm, covered by a layer of the peritoneum are called true coelomates. In this case, the membranes adjacent to the body wall and alimentary canal are called parietal and visceral membranes respectively. True coelomates are thought to be relatively advanced animals. For example - Mollusca Annelida, Arthropoda, Echinodermata, Hemichordata, and Chordata. When the true body cavity of animals is filled with blood it is called hemocoel and animals are called haemo coelomate. For example: - Mollusca and Arthropoda animals.
Figure: a) Coelomate, b) Pseudocoelomate, c) Acoelomate(Adapted URL: https://www.pmfias.com/classification-Animalia-animal-kingdom)
Importance of Coelom:
The importance of Siloam in different animal bodies is also different-
- It separates the body wall from the alimentary canal.
- It contains the internal organs of the body.
- It provides the necessary space for organ or organ growth.
- It aids in circulation, waste retention, and elimination;
- Coelom causes swelling of the circulatory system.
- Earthworms, acts as a hydrostatic skeleton.
10. Tagmatization:
Some organisms are externally segmented but in many cases, the segments are not obvious; Rather, the segments join together and divide into specific regions or tagma (tagma, pl. tagmata) in the body. Such division is called regionalization or tagmatization. Such divisions occur in the bodies of Arthropoda animals and regionalization is important in their classification. For example, the body of Insecta class animals (grasshoppers, arshola, bees, etc.) is divided into three tags, head, thorax, and abdomen, and the head and thorax of Crustacea class animals (shrimp) are divided into cephalothorax and abdomen. divided Arachnid (spider) body parts combine to form two tagma called prosoma and opisthosoma. The evolutionary process of territorialization in animals is called tagmosis.
11. Notochord:
A band of somewhat flexible, elastic, and porous tissue located along the midline of the body surface in the embryo or throughout life is called a notochord. Animals that have a notochord are called chordate animals. Animalia is mainly divided into two groups based on the presence or absence of notochord. Namely-
- Non-chordate: Animals in which notochord is absent are called non-chordate. For example, it includes all animals from Porifera to Echinodermata.
- Chordate: Organisms in which notochords are present are called chordates. For example, All animals of the order Chordata.
12. Way of living:
Based on their way of life, animals can be mainly divided into two groups, namely-
Free-living: They move freely and live without mutual cooperation or companionship. Examples:- Copsychus saularis (dove), and Columba livia (pigeon).
Parasites: They live by taking shelter in other animals and absorbing food. Examples: Ascaris lumbricoides (roundworm), and Fasciola hepatica (flatworm).
13. Alimentary canal:
Animals can be divided into 2 groups based on the presence and absence of the alimentary canal, viz.
Parazoa: Animals that do not have a digestive tract are called Parazoa. For example - Porifera
Enterozoa: The animals which have a digestive system are called Enterozoa. For example-All animals from Cnidaria to Chordata.
14. Nutrition:
Based on the nutrition system, the animals are divided into two categories, viz.-
Autotroph: The animals that can make their own food are called autotrophs.
Heterotroph: Animals that cannot produce their own food i.e. have to depend on others for nutrition are called heterotrophs.
15. Appendages:
Appendages are protruding and movable parts of the animal body that are attached to the body and help in movement, eating, and other activities. Animals have different types of appendages that are used as a basis for classification. For example, different types of appendages of animals (invertebrates and vertebrates): tentacles, flagella, and cilia of Protozoan animals; Karshika- Cnidaria animals; Carnivorous and carnivorous animals of the order Mollusca; Parapodia of the order Annelida with CT - animals; Antennae, maxillipeds, joints, wings, stylets, cirri, telson, etc.- of animals of the order Arthropoda; Nilipeds- animals of the group Echinodermata and arms, legs, fins, wings, etc.- animals of the group Chordata. These appendages are of considerable importance as a basis of the classification.
Conclusion:
Important questions from Coelom: :
Which of the Acoelomates, Pseudocoelomates, and Eu-coelomates are relatively advanced animals?
Give your opinion.
- Group the taxa of fishes, roundworms, and tapeworms on the basis of variation in coelom with factors.
- Based on the presence and structure of specialized cavities in tapeworms, roundworms, and earthworms.
Post a Comment