NCERT Solutions for Class 11 Biology Chapter 1 The Living World
NCERT Solutions for Class 11 Biology Chapter 1 The Living World explores the characteristics of living organisms, biodiversity, necessity of biological classification, rules of Binomial Nomenclature (ICBN & ICZN), taxonomic hierarchy (species, genus, family, order, class, phylum/division, kingdom), and various taxonomical aids used in biological studies.
Overview of Topics & Subtopics (Click to Jump)
1. What is Living? & Defining Characteristics of Organisms
Short Note:
• Characteristics of Living Organisms:
- Growth: Increase in mass and number of individuals. Non-living objects can also grow externally (e.g., mountains, sand dunes), so growth is not a defining feature.
- Reproduction: Production of offspring. Infertile couples, worker bees, and mules do not reproduce, so reproduction is not a defining feature.
- Metabolism: Sum total of all chemical reactions occurring in an organism. Occurs in all living beings without exception; hence, metabolism is a defining feature.
- Cellular Organisation: Cells are the structural and functional unit of life. It is a defining feature.
- Consciousness: Ability to sense environmental stimuli and respond. It is the most technically complicated and defining feature of all living organisms.
2. Diversity in the Living World & Binomial Nomenclature
Short Note:
• Biodiversity: The range and variety of living organisms present on Earth (approx. 1.7 to 1.8 million species described).
• Nomenclature & Identification: Standardized naming of organisms so that an organism is known by the same name all over the world.
- ICBN: International Code for Botanical Nomenclature (for plants).
- ICZN: International Code of Zoological Nomenclature (for animals).
• Binomial Nomenclature (Carolus Linnaeus):
- Each scientific name has two components: Generic Name (Genus) and Specific Epithet (Species).
- Scientific names are in Latin or Latinised, written in italics when printed, or underlined separately when handwritten.
- Genus starts with a capital letter, species with a small letter (e.g., Mangifera indica Linn.).
3. Taxonomic Categories & Hierarchy (Species to Kingdom)
Short Note:
• Taxonomic Category & Taxon: Each rank or level in the classification system is termed a category/taxon (plural: taxa).
• Taxonomic Hierarchy (Ascending Order):
Species → Genus → Family → Order → Class → Phylum / Division → Kingdom
- Species: Group of individual organisms with fundamental similarities (e.g., Solanum tuberosum - potato).
- Genus: Aggregation of closely related species (e.g., Solanum includes potato, tomato, and brinjal).
- Family: Group of related genera with fewer similarities (e.g., Solanaceae includes Solanum, Petunia, Datura).
- Order: Assembly of families exhibiting a few similar characters (e.g., Polymoniales).
- Class: Group of related orders (e.g., Mammalia includes Primata and Carnivora).
- Phylum (Animals) / Division (Plants): Classes sharing common features like presence of notochord.
- Kingdom: Highest category (e.g., Kingdom Plantae, Kingdom Animalia).
4. Taxonomical Aids
Short Note:
• Herbarium: Storehouse of collected plant specimens that are dried, pressed, and preserved on sheets, carrying labels with collection date, place, local/scientific names, family, and collector's name.
• Botanical Gardens: Specialized gardens having collections of living plants for reference (e.g., Royal Botanical Garden, Kew, England; Indian Botanical Garden, Howrah).
• Museum: Repositories containing preserved plant and animal specimens in jars with preservative solutions or as dried/stuffed specimens.
• Zoological Parks (Zoos): Enclosed places where wild animals are kept in protected environments under human care.
• Taxonomic Key: Aid used for identification based on similarities and dissimilarities, using contrasting characters in a pair called a couplet. Each statement in the key is called a lead.
Intext & Conceptual Questions
1. Growth: Growth is defined as an increase in body mass and cell number. Non-living objects like mountains, sand dunes, and boulders also grow by the accumulation of material on their surface (extrinsic growth). Hence, growth cannot be considered a defining feature.
2. Reproduction: While reproduction is characteristic of living organisms, many living organisms do not reproduce at all (e.g., mules, sterile worker bees, infertile human couples). Furthermore, no non-living object is capable of reproducing. Therefore, reproduction is a general characteristic but not an absolute defining property of life.
Textbook Chapter End Exercise Questions
Binomial Nomenclature: It is the scientific system of naming organisms using a two-word format, introduced by Carolus Linnaeus. The first word represents the Genus and the second word represents the Specific Epithet (Species).
Universal Rules of Nomenclature:
1. Biological names are generally in Latin and written in italics.
2. The first word denotes the Genus and starts with a Capital letter, while the second word denotes the Species and starts with a small letter.
3. When handwritten, both words are underlined separately, or printed in italics to indicate their Latin origin.
4. Name of the author appears at the end of the specific epithet in an abbreviated form (e.g., Mangifera indica Linn.).
• Example: Human = Homo sapiens, Mango = Mangifera indica.
Taxonomic Key: A taxonomic key is an artificial analytical tool used by biologists to identify unknown plants and animals based on their similarities and dissimilarities.
Key Features and Utility:
1. It is based on a pair of contrasting characters called a couplet.
2. Out of the two options in a couplet, one statement is accepted while the other is rejected based on the specimen's observed traits.
3. Each individual statement in the key is called a lead.
4. Separate taxonomic keys are required for each taxonomic category (such as Family, Genus, and Species) for identification purposes.
5. Keys are analytical in nature and allow scientists to systematically narrow down and correctly classify unknown biological specimens.
Read More & Chapter Resources
These short notes are designed for quick revision. Read the main points once, then use the related material below to practise the same chapter. Revising a concept and checking it with questions can make your preparation more focused.