Class 9 Science
Question: 1. What are the advantages of classifying organisms?
Answer: There are millions of species on this earth. For anybody, it is impossible to study about each of them in his lifetime. Classification makes it easy to study the organisms; on the basis of certain common characters.
Question: 2. How would you choose between two characteristics to be used for developing a hierarchy in classification?
Answer: We need to look at the fact if given character is present in a small number of organisms or a larger number of organisms. In the first case, the commonality of characters would represent a species. In the latter case, the commonality of characters would represent a higher taxa; like genus, family, order or phylum.
Question: 3. Explain the basis for grouping organisms into five kingdoms.
Answer: Following points explain the basis of grouping organisms into five kingdoms.
Organization of nucleus: Organisms with unorganized nucleus are kept under the kingdom Monera. Those with organized nucleus are kept in other kingdoms.
Number of cells: Unicellular eukaryotes are kept in the kingdom Protista, while multicellular eukaryotes are kept in other kingdoms.
Mode of nutrition and presence of cell wall: Hetereotrophic organisms in which cell wall is present are taken under the kingdom fungi. Autotrophic organisms in which cell wall is present are taken in the kingdom Plantae. Organisms in which cell wall is absent are taken in the kingdom Animalia.
Question: 4. What are the major divisions in the Plantae? What is the basis for these divisions?
Answer: The major divisions of Plantae and the basis for these divisions are as follows:
Question: 5. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
Answer: In the plant kingdom, morphological characters are taken into consideration while deciding about the divisions. Morphology is the study of shapes and forms of various parts. In the animal kingdom, anatomical characters are taken into consideration while deciding about subgroups. Anatomy is the study of various organs’ design in animals.
Question: 6. Explain how animals in Vertebrata are classified into further subgroups.
Answer: Vertebrates are classified into further subgroups on following bases:
Super Class Tetrapoda has been further classified into following classes:
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