Important questions based on NCERT syllabus for Chapter 1 - The Living World:
Question-1: Why are the classification systems changing every now and then?
Solution: From very early days till now biologists use several characters for classification system. These are morphology, anatomy, cytology, physiology, ontogeny, phylogeny, reproduction, biochemistry, etc. But day by day biologists are learning something new about organisms from their fossil records and using” advanced study techniques such as molecular phylogeny, etc. So their point of view about classification keeps changing. Thus the system of classification is modified every now and then.
Question-2: Define a taxon. Give some example of taxa at different hierarchical levels.
Solution: A taxonomic unit in the biological system of classification of organism is called taxon (plural taxa). For example a phylum, order, family, genus or species represents taxon. It represents a rank. For example, all the insects form a taxon. Taxon of class category for birds is Aves and taxon of Phylum category for birds is Chordata. The degree of relationship and degree of similarity varies with the rank of the taxon. Individuals of a higher rank, say Order or Family, are less closely related than those of a lower rank, such as Genus or Species.
Question-3: How is a key helpful in the identification and classification of an organism?
Solution: ‘Key is an artificial analytic device having a list of statements with dichotomic table of alternate characteristics. Taxonomic keys are aids for rapid identification of unknown plants and animals based on the similarities and dissimilarities. Keys are primarily based on stable and reliable characters. The keys are helpful in a faster preliminary identification which can bebacked up by confirmation through comparison with detailed description of the taxon provisionally identified with. Separate taxonomic keys are used for each taxonomic category like Family, Genus and Species.