NCERT Solutions for Class 11 Biology Chapter 1: The Living World (NCERT 2026–27)
These Class 11 Biology Chapter 1 solutions cover The Living World, the opening chapter of Unit 1 (Diversity in the Living World). The chapter explains why we classify living organisms, the meaning of nomenclature, identification, classification, taxonomy and systematics, the rules of binomial nomenclature, and the taxonomic categories from species up to kingdom. Below you will find every NCERT exercise question reproduced verbatim and answered in clear, exam-ready prose, updated for session 2026–27.
Class: 11Subject: BiologyUnit: 1 – Diversity in the Living WorldChapter: 1Chapter Name: The Living WorldSession: 2026–27
The Living World introduces the science of life and the enormous biodiversity around us — between 1.7 and 1.8 million species have been described so far. Because local names vary from place to place, biologists developed a standard way of naming every organism, called nomenclature, governed by the ICBN (for plants) and the ICZN (for animals). Each scientific name has two parts — a generic name and a specific epithet — the system of binomial nomenclature given by Carolus Linnaeus (for example, Mangifera indica for mango). The chapter then explains classification, taxonomy and systematics, and finally describes the taxonomic hierarchy: species, genus, family, order, class, phylum/division and kingdom, in ascending order. As we move up the hierarchy, the number of shared characters decreases.
Key Concepts & Definitions
Biodiversity: the number and types of organisms present on earth; roughly 1.7–1.8 million species have been identified and described, with new ones being found continuously.
Nomenclature: the process of standardising the naming of living organisms so that one organism is known by the same name all over the world. Plant names follow the International Code for Botanical Nomenclature (ICBN) and animal names the International Code of Zoological Nomenclature (ICZN).
Identification: determining correctly which known organism a given specimen is, so that the right name can be attached to it.
Binomial nomenclature: the two-word naming system given by Carolus Linnaeus — the first word is the genus (generic name) and the second is the specific epithet, e.g. Mangifera indica.
Classification: the process of grouping organisms into convenient categories (taxa) based on easily observable characters.
Taxon (plural: taxa): a unit or group representing a rank in classification, e.g. mammals, dogs, wheat, insects — taxa exist at different levels of the hierarchy.
Taxonomy: the science of classification, based on characterisation, identification, classification and nomenclature, using external/internal structure, cell structure, development and ecology.
Systematics: the study of the diversity of organisms and all their comparative and evolutionary relationships; the word comes from the Latin systema (systematic arrangement).
Taxonomic hierarchy: the arrangement of taxonomic categories in a definite order — species → genus → family → order → class → phylum/division → kingdom. Higher categories share fewer common characters.
Rules of binomial nomenclature
Biological names are generally in Latin and written in italics (or Latinised), irrespective of their origin.
The first word denotes the genus and the second denotes the specific epithet.
When handwritten, both words are separately underlined; in print they are in italics, to show their Latin origin.
The genus name starts with a capital letter; the specific epithet starts with a small letter — e.g. Mangifera indica.
The author’s name appears (abbreviated) after the specific epithet, e.g. Mangifera indica Linn.
The table below (from NCERT Table 1.1) shows the taxonomic categories of some common organisms.
Common Name
Biological Name
Genus
Family
Order
Class
Phylum/Division
Man
Homo sapiens
Homo
Hominidae
Primata
Mammalia
Chordata
Housefly
Musca domestica
Musca
Muscidae
Diptera
Insecta
Arthropoda
Mango
Mangifera indica
Mangifera
Anacardiaceae
Sapindales
Dicotyledonae
Angiospermae
Wheat
Triticum aestivum
Triticum
Poaceae
Poales
Monocotyledonae
Angiospermae
NCERT Exercises — Solutions
All questions below are reproduced verbatim from the NCERT textbook. The answers are original and written in CBSE exam-ready style.
1. Why are living organisms classified?
ANSWERThere are millions of living organisms on earth — between 1.7 and 1.8 million species have already been described — and it is nearly impossible to study each one individually. Classification is therefore necessary for the following reasons:(i) It makes the study of such a wide variety of organisms simple and systematic by grouping them into convenient categories based on shared characters.(ii) It helps us identify an organism quickly and place it correctly in relation to others.(iii) It reveals the similarities and differences among organisms and shows the evolutionary relationships between them.(iv) It helps in the study of other groups of organisms by comparison, and is useful in fields such as agriculture, forestry, medicine and the conservation of bio-resources.
2. Why are the classification systems changing every now and then?
ANSWERClassification systems keep changing because our knowledge of organisms is constantly increasing. As we explore new areas and re-examine old ones, new organisms are continuously being discovered, identified and described.Earlier classifications were based mainly on a few easily observable external (morphological) characters and even on the ‘uses’ of organisms. With the development of new techniques, scientists now study internal structure, cell structure, development processes, ecology and even molecular and genetic data. As this fresh information comes in, the relationships between organisms are better understood, and the classification system has to be revised and updated to reflect their true evolutionary relationships.
3. What different criteria would you choose to classify people that you meet often?
ANSWERPeople we meet often can be classified using several practical criteria, depending on the purpose. Common bases include:(i) Relationship — family members, relatives, friends, classmates, neighbours.(ii) Profession or occupation — teachers, doctors, shopkeepers, students, farmers.(iii) Place of residence — people from the same locality, city or region.(iv) Age group — children, teenagers, adults, elderly people.(v) Gender, language or interests — such as people who share a hobby or speak the same language.Any one of these criteria, or a combination, allows us to group people in a way that is convenient for a particular need. (Your own reasonable criteria are accepted.)
4. What do we learn from identification of individuals and populations?
ANSWERIdentification of individuals and populations gives us detailed knowledge of their characteristics, which is essential for naming and classifying them correctly. From such identification we learn:(i) The similarities and dissimilarities among individuals of the same kind and between different kinds of organisms.(ii) The correct scientific name to assign to an organism, so that it can be referred to uniformly all over the world.(iii) The relationships of an organism with other organisms, which helps in grouping them into proper taxa and in tracing evolutionary links.(iv) Useful information about our bio-resources and their diversity, which is valuable in agriculture, forestry, industry and conservation.
5. Given below is the scientific name of Mango. Identify the correctly written name.Mangifera IndicaMangifera indica
ANSWERThe correctly written name is Mangifera indica.According to the rules of binomial nomenclature, the first word (the genus, Mangifera) begins with a capital letter, while the second word (the specific epithet, indica) begins with a small letter. Therefore “Mangifera Indica”, with a capital ‘I’ in the specific epithet, is incorrect.
6. Define a taxon. Give some examples of taxa at different hierarchical levels.
ANSWERTaxon: A taxon (plural: taxa) is a unit or group of organisms used in classification that represents a particular rank or category in the taxonomic hierarchy. Each taxon is a distinct biological entity, not merely a morphological aggregate.Examples at different hierarchical levels: ‘Insecta’ (class) and ‘Mammalia’ (class) are taxa at the class level; ‘Plants’ and ‘Animals’ are taxa at the kingdom level; ‘Dogs’ (genus Canis) is a taxon at the genus level; and Homo sapiens is a taxon at the species level. Thus taxa such as ‘dogs’, ‘mammals’ and ‘animals’ represent ranks at progressively higher levels.
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
ANSWERThe correct sequences (in ascending order, where each category includes the one before it) are (a) Species → Order → Phylum → Kingdom and (c) Species → Genus → Order → Phylum.In both (a) and (c), the categories follow the proper hierarchy from lower to higher (species being the lowest). Option (b) is incorrect because it places genus before species, whereas species is the lowest category and must come first.
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.
ANSWERGeneral (taxonomic) meaning: A species is a group of individual organisms with fundamental similarities that can be distinguished from other closely related species on the basis of distinct morphological differences. The specific epithet in a binomial name represents the species, e.g. indica in Mangifera indica.In higher plants and animals (biological species concept): A species is a group of organisms that can naturally interbreed among themselves to produce fertile offspring but are reproductively isolated from other such groups. Here morphology and the ability to reproduce sexually are the key criteria.In bacteria: The biological species concept cannot be applied easily because bacteria mostly reproduce asexually (by binary fission) and do not interbreed in the usual sense; they also exchange genetic material by other means. Therefore, bacterial species are defined mainly on the basis of biochemical, physiological, nutritional and molecular (genetic) characters rather than interbreeding. (Discuss further examples with your teacher.)
9. Define and understand the following terms:(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus
ANSWER(i) Phylum: A higher taxonomic category that includes related classes. In animals, classes such as fishes, amphibians, reptiles, birds and mammals are grouped into the phylum Chordata on the basis of common features like the presence of a notochord and a dorsal hollow neural system. (In plants the equivalent category is called Division.)(ii) Class: A category that includes related orders. For example, the order Primata (monkey, gorilla, gibbon) and the order Carnivora (tiger, cat, dog) are placed together in the class Mammalia.(iii) Family: A category containing a group of related genera with fewer similarities than those within a genus or species. For example, the genera Solanum, Petunia and Datura are placed in the family Solanaceae; the genera Panthera and Felis are placed in the family Felidae.(iv) Order: A higher category that is an assemblage of related families sharing a few common characters. For example, the families Felidae and Canidae are placed in the order Carnivora; the plant families Convolvulaceae and Solanaceae are placed in the order Polymoniales on the basis of floral characters.(v) Genus: A category comprising a group of related species that have more characters in common with one another than with species of other genera. For example, lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris) all belong to the genus Panthera.
10. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.
ANSWERThe taxonomical hierarchy is the arrangement of taxonomic categories in ascending order, from species (the lowest) up to kingdom (the highest). Each higher category includes the one below it, and as we move upward the number of shared characters decreases. This is best illustrated using one plant (wheat) and one animal (man).The table below shows the complete hierarchy for both examples.
Category
Plant – Wheat
Animal – Man
Kingdom
Plantae
Animalia
Division / Phylum
Angiospermae (Division)
Chordata (Phylum)
Class
Monocotyledonae
Mammalia
Order
Poales
Primata
Family
Poaceae
Hominidae
Genus
Triticum
Homo
Species
aestivum
sapiens
Thus the scientific name of wheat is Triticum aestivum and of man is Homo sapiens. Reading from species upward shows how each organism is placed step by step into higher and broader taxonomic categories.
Extra Practice Questions
Short Answer Type Questions
Q1. What is meant by binomial nomenclature? Who introduced it?
ANSWERBinomial nomenclature is the system of giving each organism a scientific name made of two words — the genus (generic name) and the specific epithet. It was introduced by Carolus Linnaeus and is practised by biologists all over the world, e.g. Mangifera indica.
Q2. Distinguish between ICBN and ICZN.
ANSWERICBN stands for the International Code for Botanical Nomenclature and lays down the rules for naming plants. ICZN stands for the International Code of Zoological Nomenclature and lays down the rules for naming animals. Both ensure that each organism has only one valid scientific name accepted worldwide.
Q3. What is the difference between identification and nomenclature?
ANSWERIdentification is the process of correctly recognising and describing an organism so that we know exactly what it is. Nomenclature is the process of assigning a standard, universally accepted name to that correctly identified organism. Nomenclature is possible only after identification.
Q4. Why are biological names written in Latin?
ANSWERBiological names are generally in Latin (or Latinised) and written in italics because Latin is a ‘dead’ language whose words no longer change in meaning. This makes the names stable and uniform across all countries and languages, irrespective of the origin of the word.
Q5. Define systematics. From which word is it derived?
ANSWERSystematics is the branch of biology that deals with the diversity of organisms and their identification, nomenclature, classification and evolutionary relationships. The word is derived from the Latin word systema, meaning the systematic arrangement of organisms; Linnaeus used Systema Naturae as the title of his publication.
Long Answer Type Questions
Q1. Explain the basic processes that are fundamental to taxonomy.
ANSWERTaxonomy is based on four interlinked processes. Characterisation is the study of the external and internal structure, cell structure, development process and ecological information of an organism to describe its features. Identification is the correct recognition of an organism on the basis of these characters. Classification is the grouping of organisms into convenient categories (taxa) according to their similarities and differences. Nomenclature is the assignment of a standard scientific name, following the ICBN for plants and the ICZN for animals. Together these processes allow biologists worldwide to study, name and arrange the enormous diversity of life in a systematic way.
Q2. Describe the taxonomic categories from species to kingdom and explain how the number of common characters changes along the hierarchy.
ANSWERThe taxonomic categories, in ascending order, are species, genus, family, order, class, phylum (or division for plants) and kingdom. A species is a group of individuals with fundamental similarities; a genus groups related species (e.g. Panthera); a family groups related genera (e.g. Felidae); an order groups related families (e.g. Carnivora); a class groups related orders (e.g. Mammalia); a phylum/division groups related classes (e.g. Chordata); and the kingdom (Animalia or Plantae) is the highest category. As we move up from species to kingdom, the number of common characters shared by the members decreases, and it becomes more difficult to determine relationships, making classification more complex. Conversely, the lower the taxon, the more characters its members share.
Q3. Distinguish between taxonomy, classification and systematics, and explain how they are related.
ANSWERClassification is the process of arranging organisms into groups or categories (taxa) on the basis of observable characters. Taxonomy is the science of classification and is built on four processes — characterisation, identification, classification and nomenclature — using structural, developmental and ecological information. Systematics is broader still: derived from the Latin systema, it studies the diversity of organisms and all their comparative and evolutionary relationships, and its scope was later enlarged to include identification, nomenclature and classification. Thus classification is one step within taxonomy, and taxonomy in turn forms part of the wider field of systematics, which additionally emphasises evolutionary links between organisms.
MCQs & Assertion–Reason
1. The number of species described so far ranges between:
(a) 1.7–1.8 thousand (b) 1.7–1.8 lakh (c) 1.7–1.8 million (d) 17–18 million
2. Binomial nomenclature was given by:
(a) Ernst Mayr (b) Carolus Linnaeus (c) Charles Darwin (d) R.H. Whittaker
3. In the name Mangifera indica, the word ‘indica’ represents the:
(a) genus (b) specific epithet (c) family (d) order
4. The rules for naming plants are governed by:
(a) ICZN (b) ICBN (c) ICNB (d) IUCN
5. The correct ascending order of taxonomic categories is:
(a) Species → Genus → Family → Order (b) Genus → Species → Order → Family (c) Family → Order → Genus → Species (d) Order → Family → Genus → Species
6. The genus that includes lion, leopard and tiger is:
(a) Felis (b) Panthera (c) Canis (d) Homo
7. The family Felidae and the family Canidae together belong to the order:
(a) Primata (b) Carnivora (c) Diptera (d) Poales
8. As we go from species to kingdom, the number of common characters:
(a) increases (b) decreases (c) remains the same (d) first increases then decreases
9. In plants, the category equivalent to ‘phylum’ of animals is:
For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.
A-R 1. Assertion: Living organisms are classified into different taxa.
Reason: It is nearly impossible to study every organism individually, so classification makes their study simple and systematic.
A-R 2. Assertion: In a scientific name, the genus begins with a capital letter and the species with a small letter.
Reason: These are universal rules of binomial nomenclature.
A-R 3. Assertion: As we move from species to kingdom, the number of shared characters increases.
Reason: Higher categories include a smaller and more closely related group of organisms.
A-R 4. Assertion: The biological species concept is difficult to apply to bacteria.
Reason: Bacteria mostly reproduce asexually and do not interbreed in the usual sense.
A-R 5. Assertion: Systematics includes the study of evolutionary relationships between organisms.
Reason: Systematics is derived from the Latin word ‘systema’ meaning systematic arrangement of organisms.
Answer key: 1-(A), 2-(A), 3-(D), 4-(A), 5-(B).
Common Mistakes to Avoid
Watch out for these
Writing the specific epithet with a capital letter — it must be lowercase, e.g. Mangifera indica, not Mangifera Indica.
Confusing ICBN (plants) with ICZN (animals).
Mixing up the order of the hierarchy — remember species is the lowest and kingdom the highest.
Stating that common characters increase as you go up the hierarchy — they actually decrease.
Confusing taxonomy, classification and systematics — classification is one step within taxonomy, and systematics is the broadest term, emphasising evolutionary relationships.
Forgetting to write or underline scientific names correctly (italics in print, or two separate underlines when handwritten).
Exam tips for this chapter
Learn the hierarchy Species → Genus → Family → Order → Class → Phylum/Division → Kingdom by heart and remember that common characters decrease upwards. Memorise the standard NCERT examples — Mangifera indica (mango), Panthera leo/tigris/pardus, Homo sapiens, Triticum aestivum — and the families/orders linked to them (Felidae, Canidae → Carnivora). State the full rules of binomial nomenclature whenever a naming question appears, and always quote the Table 1.1 examples to support hierarchy answers.
Frequently Asked Questions
What is Class 11 Biology Chapter 1 The Living World about?
Chapter 1 introduces biodiversity and explains why and how living organisms are classified. It covers nomenclature, identification, classification, taxonomy and systematics, the rules of binomial nomenclature given by Carolus Linnaeus, and the taxonomic categories from species up to kingdom.
What is binomial nomenclature with an example?
Binomial nomenclature is the two-word naming system given by Carolus Linnaeus, where the first word is the genus and the second is the specific epithet, for example Mangifera indica for mango. The genus starts with a capital letter and the specific epithet with a small letter.
What is the correct order of taxonomic categories?
The taxonomic hierarchy in ascending order is Species, Genus, Family, Order, Class, Phylum (or Division for plants) and Kingdom. Species is the lowest and kingdom the highest category, and the number of common characters decreases as we move upward.
Are these Class 11 Biology Chapter 1 solutions free?
Yes. All solutions are free and follow the official NCERT Biology textbook for session 2026–27, with every exercise question reproduced verbatim and answered in exam-ready style.
