The Living World - Solutions of CBSE Class 11 NCERT Biology Chapter 1 Exercise Questions


CBSE Class 11 Biology - NCERT Solutions

Unit 1: Diversity in The Living World

Chapter 1, The Living World

 Solutions of CBSE Class 11 NCERT Biology Textbook Lesson 1 Exercise Questions

Question 1: Why are living organisms classified?
Solution: Organisms are classified because of the following reasons:
(i). Easy identification.
(ii). Study of organisms of other places.
(iii). Study of fossils.
(iv). Grouping helps in study of all types of organisms while it is impossible to study individually all of them.
(v). It brings out similarities and dissimilarities.
(vi). They help in knowing relationships among different groups.
(vii). Evolution of various taxa can be known.

Question 2: Why are classification systems changing every now and then?
Solution: Scientific study has been ever progressing due to continuous addition of newer tools and techniques. Earlier workers relied on only habitat and habits for classifying organisms. External morphology then became an important tool for classification. Anatomy and then embryology were used in classification. Subsequently cellular structure, chromosomes, biochemical analysis and now DNA matching are being carried out to find relationships and classify organisms. Therefore, classification systems have been changing, rather evolving with time. They have never been static.

Question 3: What different criteria would you choose to classify people that you meet often?
Solution: Different criteria are:
(i). Family members.
(ii). Relatives.
(iii). Family friends.
(iv). School mates.
(v). Classmates.
(vi). Adults, seniors, same age and juniors.
(vii). Sex.
(viii). Height.
(ix). Playmates.

Question 4: What do we learn from identification of individuals and populations?
Solution: Individuals: Each individual possesses a specific combination of traits not found in other members of the population.
(i). Each population is reproductively isolated.
(ii). Members of a population interbreed amongst themselves.
(iii). Members of a population resemble one another more than they resemble members of other populations.
(iv). Karyotype is similar in all the individuals of a population.
(v). There is a complete anatomical similarity amongst members of a population.

Unit 1: Diversity in The Living World

Lesson 1, The Living World

CBSE Class 11 Biology NCERT Solutions of Chapter 1 Exercise Questions

Question 5: Given below is the scientific name of Mango. Identify the correctly written name name Mangifera Indica, Mangifera indica.
Solution: Mangifera indica.

Question 6: Define a taxon. Give some examples of taxa at different hierarchical levels.
Solution: Taxon is a unit of classification which may represent any level of grouping of organisms based on certain common characteristics like Maize (species), Roses (genus), grasses (family), conifers (order), dicots (class), seed plants (division), etc.  The term was introduced for the first time by ICBN during 1956. Mayr (1964) has defined taxon to be a taxonomic group of any rank that is sufficiently distinct to be worthy of being assigned to a definite category. Simpson (1961) recognises taxon to be a group of real organisms recognised as a formal unit at any level of hierarchical classification. Examples,
Division  - Angiospermae
Class - Monocotyledonae
Order - Poales
Family - Poaceae
Genus - Triticum
Species - aestivum

Question 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
Solution: (c).
Species----> Genus----> Order----> Phylum
Species---> Genus---> Family---> Order---> Class---> Phylum---> Kingdom.

Question 8: Try to collect all the currently accepted meaning 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.
(i). It is a natural population or group of natural populations of individuals having similar morphology, anatomy, physiology and cytology.
(ii). It is a basic unit of classification where individuals share a common genetic set up.
(iii). Species is an assemblage of structurally similar individuals which interbreed freely amongst them but are reproductively isolated from members of other species.
Higher Plants and Animals
Higher plants and animals are sexually reproducing organisms.  The criterion of reproductive isolation can be used for them. Therefore, third definition of the species given is applicable to them. Examples, Panthera leo (lion), Panthera tigris (tiger).
The criterion of free interbreeding and reproductive isolation cannot be applied in thier case as they do not reproduce sexually. Only the first definition of the species given above can be applied for them.

Question 9: Define and understand the following terms: (i). Phylum (ii). Class (iii). Family (iv). Order (v). Genus
(i) Phylum: It is a higher grouping of organisms which is immediately below that of kingdom and possess some similar correlated characters, e.g., jointed appendages in arthropoda.
(ii) Class: It is a taxonomic grouping of organisms higher than order and lower than phylum. Class is taxon that consists of one or more orders of organisms all of which possess some similar correlated characters, e.g., Order Primata comprising monkey, gorilla and gibbon is put along with order Carnivora representing tiger, cat and dog. Both are placed in class Mammalia.
(iii) Family: Family is a grouping of organisms which is immediately below that of order and above that of genus. Family is a taxonomic category that consists of one or more genera of organisms all of which have some common correlated characters not found in genera of other orders. Among plants for example, three different genera Solanum, Petunia, and Datura are placed in the family Solanaceae. Among animals for example, genus Panthera comprising lion, tiger, leopard is put along with genus, Felis (Cats) in the family Felidae.
(iv) Order: Order is a taxonomic category having one or more families of organisms all of which possess some specific correlated characters not found in others, the families felidae and canidae are included under the order carnivora alongwith hyaenidae (hyaenas) and ursidae (bears).
(v) Genus: Genus is a grouping of organisms having one or more species all of which have common ancestry and share some common correlated characters, e.g., potato, tomato, and brinjal are there different species but all belong to the genus Solanum. Lion (Panthera leo), leopard (Panthera pardus), and tiger (Panthera tigris) with several common features, are all species of the genus Panthera.

Unit 1: Diversity in The Living World

Chapter 1, The Living World

CBSE Class 11 NCERT answers of Chapter 1 Biology textbook exercise questions

Question 10: How is key helpful in identification and classification of an organism?
Solution: Key is a table of alternate characteristics arranged sequence wise which through selection and rejection is used in classification and identification of organisms.
Classification: Keys are available for knowing the phylum / division, class, order, and family of the organisms on each system of classification. With thier help every type of organism can be classified, whether it is known or unknown.
Identification: After knowing the family, identification key is used to know the genus and then the name of the species. If the organism is not already recorded, efforts ares made first to check and recheck about its discovery and then given it a name.

Question 11: Illustrate the taxonomic hierarchy with suitable examples of a plant and an animal.
Solution: Taxonomic hierarchy is the classification of organisms in a definite sequence of taxonomic categories in a descending order starting with kingdom and ending in species.
Kingdom---> Phylum / Division---> Class---> Order---> Family---> Genus---> Species.

The table (Figure) below is examples of the taxonomic hierarchy of mango (plant) and human (animal):
Taxonomic hierarchy of mango (plant) and human (animal)
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