The VIDYANKER team has thoughtfully prepared the NCERT Solutions for Class 11 Biology Chapter 1, "The Living World" These solutions are designed to help you tackle the NCERT textbook questions with ease. We recommend going through the chapter's theory before diving into the solutions for a deeper understanding. Feel free to share these NCERT Solutions for Class 12 Biology with others—learning is always better when shared!
NCERT TEXTBOOK QUESTIONS SOLVED
1. Why are living organisms classified?
Ans. A wide range of plants, animals, and microbes exist on earth. All these living organisms vary in size, shape, colour, habitat, and numerous other characteristics. Since there are millions of living organisms on earth, it becomes impossible to study each and every one of them. Hence, scientists have evolved systems to classify all living organisms. These methods of classification are based on rules and principles that allow identification, nomenclature, and finally classification of an organism. For example, based on certain principles, once an organism is identified as an insect, it will be given a scientific name and then grouped with other similar organisms. Thus, various groups or taxon include organisms based on their similarity and differences. Therefore, the biological classification help reveals the relationship that different organisms enjoy. It makes studying organisms easy and well-organized.
Ans. A wide range of plants, animals, and microbes exist on earth. All these living organisms vary in size, shape, colour, habitat, and numerous other characteristics. Since there are millions of living organisms on earth, it becomes impossible to study each and every one of them. Hence, scientists have evolved systems to classify all living organisms. These methods of classification are based on rules and principles that allow identification, nomenclature, and finally classification of an organism. For example, based on certain principles, once an organism is identified as an insect, it will be given a scientific name and then grouped with other similar organisms. Thus, various groups or taxon include organisms based on their similarity and differences. Therefore, the biological classification help reveals the relationship that different organisms enjoy. It makes studying organisms easy and well-organized.
2. Why are the classification systems changing every now and then?
Ans. Since very early days biologists are employing many characters for the classification system. Some of these are morphology, anatomy, cytology, physiology, ontogeny, phylogeny, reproduction, biochemistry, etc. But day by day biologists are discovering something new about the organisms from their fossil records and employing "advanced study techniques like molecular phylogeny, etc." So their outlook towards classification keeps changing. Thus the system of classification is changed every now and then.
3. What different criteria would you choose to classify people that you meet often?
Ans. So, to classify this class of forty students, let us begin with the classification on the basis of sexes of the students. This will give us two major groups: one that comprises boys and the other girls. Each of these two groups can then be classified further on the basis of the names of the students falling in these groups. Since it might so occur that more than one student bears the same name, one could segregate such names along surnames. Once again, there is some likelihood that more than one student may bear the same surname, and thus the classification in its final step will depend on roll numbers of all the students.
4. What do we learn from identification of individuals and populations?
Ans. The knowledge of characteristic of an individual or its whole population helps in identification of similarities and dissimilarities among the individuals of the same kind or between different types of organisms. It helps us classify the organisms into various categories with the help of these similarities and dissimilarities.
5. Given below is the scientific name of mango. Identify the correctly written name.
Mangifera Indica Mangifera indica
Ans. The generic name of any species of the binomial system of nomenclature begins with a capital letter whereas the specific name starts with a small letter. Hence, the proper scientific name of Mango is Mangifera indica.
Ans. The generic name of any species of the binomial system of nomenclature begins with a capital letter whereas the specific name starts with a small letter. Hence, the proper scientific name of Mango is Mangifera indica.
6. Define a taxon. Give some example of taxa at different hierarchical levels.
Ans. Taxon refers to the taxonomic level of a category in living beings. For example, species is a minimum level of classification, while it progresses on to genus and then to family and order class, next phylum or division in a sequential arrangement.
Ans. Taxon refers to the taxonomic level of a category in living beings. For example, species is a minimum level of classification, while it progresses on to genus and then to family and order class, next phylum or division in a sequential arrangement.
7. Can you identify the correct sequence of taxonomical categories?
(a) Species —> Order —> Phylum —> Kingdom
(b) Genus—) Species—> OrderKingdom
(c) Species —> Genus —>Order —> Phylum
Ans. The correct sequence of taxonomical categories is
(c) i.e., Species —>Genus —> Order —> Phylum.
8. 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.
Ans. Species occupies a key position in classification. It is the lowest taxonomic category. It is a natural population of individuals or group of populations which resemble one another in all essential morphological and reproductive characters so that they are able to interbreed freely and produce fertile offsprings. Each species is also called genetically distinct and reproductively isolated natural population. As defined by Mayr (1964), species refer to the group of actually or potentially interbreeding populations that are reproductively isolated from other similar groups.
Ans. Species occupies a key position in classification. It is the lowest taxonomic category. It is a natural population of individuals or group of populations which resemble one another in all essential morphological and reproductive characters so that they are able to interbreed freely and produce fertile offsprings. Each species is also called genetically distinct and reproductively isolated natural population. As defined by Mayr (1964), species refer to the group of actually or potentially interbreeding populations that are reproductively isolated from other similar groups.
In higher plants and animals, the term 'species' is referred to as a group of individuals who are able to interbreed freely and produce fertile offsprings. However, in case of bacteria, interbreeding cannot serve as the best criterion for delimiting species because bacteria often reproduce asexually. Conjugation, transformation and transduction, referred to as the sexual reproduction methods in bacteria, also do not correspond to true interbreeding. Thus, many other characters such as molecular homology, biochemical, physiological, ecological, and morphological characters are taken into account for the classification of bacteria.
9. Define and understand the following terms:
(i) Phylum (ii) Class (iii) Family
(iv) Order (v) Genus
Ans. (i) Phylum- A category higher than that of Class is Phylum. The term Phylum is used for animals. A Phylum is made up of one or more classes, e.g., the Phylum Chordata of animals contains not only the class Mammalia but also Aves (birds), Reptilia (reptiles), Amphibia (amphibians), etc. In plants the term Division is used in place of Phylum.
(ii) Class - The group of closely related orders is called class. For example: orders Primata and Carnivora belong to the class Mammalia.
(iii) Family - Family is a taxonomic group containing one or more related genera. In plants, families are categorized on the basis of vegetative and reproductive features.
(iv) Order - The group contains one or more related genera. Thus, the plant Family Solanaceae falls under the Order Polemoniales with four other related families like Convolvulaceae, Boraginaceae, Hydrophyllaceae, and Polemoniaceae. Similarly, under the Order Carnivora fall the animal families Felidae and Canidae, with Hyaenidae-hyenas and Ursidae-bears.
(v) Genus - It is a group or assemblage of related species which resemble one another in certain correlated characters. Correlated characters are those similar or common features which are used in delimitation of a taxon above the rank of species. All the species of genus are presumed to have evolved from a common ancestor. A genus may have a single living species e.g., Genus Homo. Its genus is Homo sapiens – the living or modem man. The Genus Felis has many species, e.g., F. domestica – common cat, F. chaus (jungle cat) etc.
10.How is a key helpful in the identification and classification of an organism?
Ans. Key is taxonomical aid used in identification of plants and animals based on the similarities and dissimilarities. In this method 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 a clue if an animal belongs to mammalian or not.
11.Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.
Ans. There exist different taxa which are arranged in a hierarchical order, and that hierarchy shows different levels of kinship. The number of similar characteristics of categories decreases from the lowest rank to the highest rank. The hierarchical system of classification was given by Linnaeus.
Ans. There exist different taxa which are arranged in a hierarchical order, and that hierarchy shows different levels of kinship. The number of similar characteristics of categories decreases from the lowest rank to the highest rank. The hierarchical system of classification was given by Linnaeus.
The major categories are in the order of hierarchy below:
Species —►Genus-►Family —► Order—► Class
Kingdom -4— Phylum or Division
Increasing specificity – ► Decreasing specificity
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
