CLASS XI BIOLOGY - Excellup.com

Finish Line & Beyond

CLASS XI BIOLOGY The Living World 1. Why are living organisms classified? Answer: The diversity of living beings makes it a challenge to systematically study them. Classification is a helpful tool to categorize them based on certain common characteristics. This enables scientists to study them in a more systematic way. The study of living beings is essential for the benefit of humankind. Discovery of new medicines, and better yielding crop varieties can be made possible only by systematic study of living beings. Moreover, environmental protection also makes it necessary for us to study the living beings in a systematic way. 2. Why are the classification systems changing every now and then? Answer: In any branch of science nothing is written in concrete. Theories keep on changing as more relevant and correct theory are being discovered. In case of living beings certain species become extinct and some new species is being formed in every era. This process of addition and deletion of species necessitates the continuous change of the classification system. 3. What different criteria would you choose to classify people that you meet often? Answer: In our day to day life we categorize people based on following criteria: 1. 2. 3. 4. 5. 6. 7.

Level of education Profession Height and skin colour Native Place Sex Hobbies Nature

4. What do we learn from identification of individuals and populations? Answer: In a diverse country like India we can learn following things from identification of individuals and population: 1. 2. 3. 4. 3. 4. 5.

Native Place. Mother Tongue Costumes Cuisine Religion Caste Socio-economic Background

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Finish Line & Beyond 5. Given below is the scientific name of Mango. Identify the correctly written name. Mangifera Indica Mangifera indica Answer: Mangifera indica 6. Define a taxon. Give some examples of taxa at different hierarchical levels. Answer: A taxon is a particular level of hierarchy in the system of classification of living beings. The following figure gives taxa at different hierarchical levels:

Kingdom Phylum Class Order Family Genus Species 7. 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: As clear from the table in previous answer, (a) and (c) is showing the correct order. 8. Define and understand the following terms: (i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus Answer: (i) Phylum: Phylum comes next to Kingdom in the taxonomical hierarchy. All broad characteristics of an animal or plant are defined in a phylum. For example all chordates have a notochord and gill at some stage of life cycle. Similarly all arthopods have jointed legs made of chitin. (ii) Class: A class includes related orders. Class defines more detailed characters other than broad architecture. For example all mammals have mammary glands to secrete milk, have hairy body. All birds or aves have pneumatic bones to assist in flying. The common character among them is the presence of notochord thereby making them members of the same phylum.


Finish Line & Beyond (iii) Order: Order further zeroes down on characteristics and includes related genus. For example humans and monkeys belong to the order primates. Both humans and monkeys can use their hands to manipulate objects and can walk on their hind legs. (iv) Genus: comprises a group of related species which has more characters in common in comparison to species of other genera. We can say that genera are aggregates of closely related species. For example, potato, tomato and brinjal are three different species but all belong to the genus Solanum. Lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris) with several common features, are all species of the genus Panthera. This genus differs from another genus Felis which includes cats. 9. How is a key helpful in the identification and classification of an organism? Answer: Keys are pairs of two contrasting characters. Selection of one character leads to rejection of another character while identifying a particular species or genera or family and so on. For example presence or absence of hair on body can give aclue if an animal belongs to mammalian or not. 10. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal. Answer: Taxonomical Hierarchy 1. Man Phylum: Chordata Class: Mammalia Order: Primata Family: Hominidae Genus: Homo Species: Homo sapiens 2. Mango Phylum: Angiosperm Class: Dicotyledons Order: Sapindales Family: Anacardiaceae Genus: Mangifera Species: Mangifera indica
