Chapter 1

  The Living world  



Q1. Why are living organisms classified?
Answer:  The living world is rich in variety so it is impossible to study all the living beings. So, living organisms are classified because of the following reasons: helps in easy identification, study of organisms of different places, study of fossils, grouping helps in study of all types of organisms, helps in showing dissimilarities and similarities, relationships and evolution of various taxa.



Q2. Why are the classification systems changing every now and then?
Answer:  Biologists use many characters for classification system from very early days until now. These are anatomy, morphology, ontogeny, cytology, physiology, reproduction etc. but scientists discover something new about organisms from their fossil records and use advance research methods such as molecular phylogeny, etc.  So, their view point about classification keeps on changing. Thus, the classification system is modified every now and then.



Q3.  What different criteria would you choose to classify people that you meet often?
Answer: The various criteria that can be used for classifying people whom we meet often are morphology, behaviour, relatives, family members, geographical location etc.



Q4. What do we learn from identification of individuals and populations?
Answer:  The knowledge of individual’s characteristics or its entire population helps to distinguish similarities and dissimilarities among individuals of same kind or between different types of organisms. This allows us to identify the organisms according to certain similarities and dissimilarities in various categories.



Q5. Given below is the scientific name of Mango. Identify the correctly written name.
Mangifera Indica
Mangifera indica
Answer:  The correctly written scientific name of Mango is Mangifera indica .



Q6. Define a taxon. Give some examples of taxa at different hierarchical levels.
Answer: A taxonomic unit in the biological classification system of organism is called taxon. For e.g. A phylum, order, family, genus, or species. It represents a rank. All insects are also forms the example of taxon. Taxon of class category for birds is Aves and taxon of Phylum category for birds is Chordata. The degree of relation and the degree of similarity differ with the rank of the taxon.


Q7. Can you identify the correct sequence of taxonomical categories?
a) Species      Order          Phylum       Kingdom
b) Genus        Species      Order          Kingdom
c) Species      Genus        Order          Phylum
Answer: 
a) The correct answer is   Species      Genus        Order          Phylum



Q8. Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in case of higher plants and animals on one hand and bacteria on the other hand.
Answer: In taxonomy, species occupies the lowest category. In plants and animals, it is the group of population which is similar to one another in their morphological and reproductive characters so they can interbreed to produce offspring. In bacteria, interbreeding does not occur because bacteria reproduce asexually.




Q9. Define and understand the following terms:
i. Phylum       ii. Class      iii. Family       iv. Order       v. Genus
Answer: 
i. Phylum - The ‘Phylum’ term is used for animals it is formed of one or more classes. It higher category than class.  
ii. Class – A class is made of one or more related orders.
iii. Family – Family is a group which contains one or more related genera. All the genera have some common features.
iv. Order – The category includes one or more related families.
v. Genus – Genus is a group of related species in certain correlated characters which resemble each other.



Q 10. How is a key helpful in the identification and classification of organisms?
Answer: Key is an artificial system that has a list of alternative characteristic statements with a dichotomic table. Taxonomic key helps to easily classify unknown plants and animals based on the similarities and dissimilarities. Keys depend on stable and reliable characters. Keys also help in identification.



Q11. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.
Answer:  The arrangement of different taxa in a hierarchical order is called taxonomic hierarchy.
Example: 
• Classification of a plant (Wheat):
Kingdom – Plantae
Division  - Angiospermae
Class – Monocotyledonae
Order – Poales
Family – Poaceae
Genus – Triticum
Species - aestivum
• Classification of an animal (Housefly):
Kingdom – Animalia
Phylum – Chordata
Class – Insecta
Order – Diptera
Family – Muscidae
Genus – Musca
Species - domestica




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