Write all the points for the basis of classification of animal kingdom.
Asked by Vishalgarg1234 | 29th Nov, 2018, 05:12: PM
The different basis of animal classification is explained below:
1. Symmetry- Animals show two types of symmetry- Radial symmetry: A symmetry where any plane passing through the central axis divides the body into two equal halves. Example- Coelenterates, ctenophores and echinoderms. Bilateral symmetry: Only a single plane divides the body into two equal halves, e.g. annelids, arthropods, molluscs, etc.
2. Levels of Organisation- Though animals are multicellular, the level of organization of cells varies from one animal to another. For example, Poriferans have a loose mass of cells and show the cellular level of organization. As we move on, colenterates have tissue level of organisation. Phylum Platyhelminthes and Aschelminthes have organ level of organization. Nor-chordates such as Annelids, Arthropods, Molluscs, Echinoderms, and Chordates have specialised organ system for their physiological activities.
3. Diploblastic and Triploblastic Organisation: Based on the number of embryonic layers, animals are classified into two- diploblastic and triploblastic animals. Diploblastic animals: The cells form two embryonic layers, i.e., an outer layer- ectoderm and an inner layer – endoderm, e.g. Phylum Coelenterata. Triploblastic animals: cells are arranged in three embryonic layers- ectoderm, endoderm and a middle layer – mesoderm. Animals belong to Phyla Platyhelminthes to Chordata have a triploblastic organisation.
4. Coelom- Coelom is a cavity between the body wall and gut wall, lined by mesoderm. Depending on presence/absence of coelom, animals have been classified into: coleomate, acoelomate and pseudocoelomate. Coelomate: Coelom is present. Eg- Annelida, Mollusca. Pseudocoelomate: mesoderm appears as pouches between endoderm and ectoderm. But the cavity formed is not lined by mesoderm. Eg- Aschelminths. Aceolomate: Coelom is absent. Example- Platyhelminthes
Answered by Sivanand Patnaik | 30th Nov, 2018, 09:25: AM
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