biology-notes-animal-kingdom

1. ANIMAL KINGDOM

2. Basis of classification The classification of the animal kingdom is based on the different essential characteristics such as level of organization, habitat, symmetry. Levels of Organization Cellular Level of Organization Tissue Level of Organization Organ Level of Organization Organ system Level of Organization • • • • Patterns of organ systems Digestive System (Incomplete Digestive System and Complete Digestive System) Circulatory System Open Type Closed Type Body symmetry Bilateral Symmetry Radial Symmetry Asymmetrical me metrical • • • • Sy Sy Sy Sy Sy Sy Symm mm mm mm mmet ym ymmetry etry ry ry ry • • • Levels of Organisation on on on All members of Animalia are multicellular, heterotrophic eukaryotes. But, all of them do not exhibit the same pattern of organization of cells. The cells in their body are of several types. These are organized into several functional units of progressively increasing complexity. in in in in incr cr cr cr crea ea ea ea ea ea easing ng ng ng ng ng ng ng ng ng ng ng c c c c c c c c c c c c c c c com om om om om om om om om om om om ompl pl plex ex ex ex ex exit it it ity. y. y. y. of of A A A Ani ni ni ni nima ex ex exhi hi hi hi hibi bi bi bit t t t th se seve vera ra ra ra ra ra ra ral l l l l l l ty ty ty ty ty ty type ma ma ma mali li li li lia th th the a a a a ar e e sa sa sa sa same pe pe pe pe pe pe pe pe pe pe pes. s. s. s. s. s. T T T T T T The ar ar are me me me me me p he he he he he he hese e mu mu mult lt lt ltic ic icel el el el el el ellu lu lu lu lula la la lar, r, r, r, r, r, he p p p p pat at at at at atte te te te tern rn rn rn o se a a a are re o he he he he hete or or or or or orga ga ga ga ga gani ni ni niza rgan an aniz iz iz iz ized ro ro ro rotr tr tr tr tr tr trop za za zati ti ti tion ed ed ed ed i i i int nt nt nt nt nto te te te te tero op op op ophi hi hi hi hic on on on o o se se se se seve c c c c c eu eu eu eu eu euka o of f f ce ce ce ce cell ll ll lls. s. The ve ve vera ral l l l l fu ka ka ka karyot o o of f f f f f f or o o org rg rg fu fu fu fu func nc Cellular Level In this level, the body shows some division of labour among cells. They are remarkably independent and can change their form and function. It is found in sponges. The body consists of many cells arranged as loose cell aggregates but, the cells do not form tissues. Tissue Level Here, in coelenterates, the arrangement of cells is more complex. The cells performing the same function are arranged into tissues, hence is called tissue level of organization. Organ Level In Platyhelminthes and other higher phyla, tissues are grouped together to form organs, each specialized for a particular function, i.e., organ level organization is present. Organ System Level In animals like annelids, arthropods, molluscs, echinoderms and chordates, organs have associated to form functional systems, each system concerned with 3

3. a specific physiological function. This is called organ system level of organisation. Organ systems in different groups of animals exhibit various patterns of complexities. Like the digestive system in Platyhelminthes has only a single opening to the outside of the body that serves as both mouth and anus and is thus, called incomplete. A complete digestive system has two openings, i.e., mouth and anus. Symmetry The symmetry refers to the arrangement of parts on the opposite sides of the body of a three dimensional animal. On the basis of symmetry, animals can be of following types: Asymmetrical: Animals in which, any plane passes through the center does not divide them into equal halves such animals are called asymmetrical, e.g., Sponges. Symmetrical: The body of some animals can be divided into two similar equal halves by one or more planes. Such animals are called symmetrical The symmetry can be further divided as: Radial Symmetry When any plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry, e.g., Coelenterates, ctenophores and echinoderms. s, s, ctenophor or or ores es es a a a and nd nd e e ech ch ch ch ch chin in in inod e e e e e fu fu fu fu further divided as: la lane passing o o two iden ng ng ng t en en enti ti ti ti tica t t t t thr ca ca ca cal l l ha hrou ou ou ough gh gh gh t ha halv lv lves t t t the he he he he c es es, , , , it it it i od od oder c c cen en en entr tr tr tral al al al a i is s call ll ll lled er erms ms ms ms. . . a a axi xi xis s s s of ed ed ed radial symm of of of of of the bod Bilateral Symmetry: In some animals, body can be divided into identical left and right halves in only one plane. This is called bilateral symmetry, e.g., Annelids, arthropods, etc. 4

4. Diploblastic and Triploblastic Organisation Germ layers are group of cells behaving as a unit during early stages of embryonic development. It differentiate to give rise to all the tissues/ organs of the fully formed individuals. On the basis of germ layers animals are classified as follows: 5

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