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NCERT Solutions - Class 11 Biology Chapter 1: The Living World

Exercises
Q1. Why are living organisms classified?
Answer - Living organisms are classified to make their study easier and more systematic.

  • There is a huge diversity of living organisms on Earth.
  • Classification helps in organizing them into groups based on similarities and differences.
  • It allows scientists to study the characteristics, relationships, and evolutionary history of organisms efficiently.
  • It also helps in identifying new species and understanding biodiversity.
Q2. Why are the classification systems changing every now and then?
Answer - Classification systems change because of advancements in science and technology.

  • New tools like molecular biology and genetic studies provide more accurate data about organisms.
  • Discovery of new species and re-evaluation of old ones lead to changes.
  • Phylogenetic classification based on evolutionary relationships replaces earlier artificial systems.
  • Hence, systems are updated to reflect our better understanding of biological relationships.
Q3. What different criteria would you choose to classify people that you meet often?
Answer - People can be classified using different observable criteria.

  • Based on age: children, adults, elderly
  • Based on profession: students, teachers, doctors, engineers
  • Based on hobbies: readers, athletes, musicians
  • Based on location: people from school, neighborhood, or workplace
  • Based on language or culture
Q4. What do we learn from identification of individuals and populations?
Answer - Identification helps in understanding various aspects of organisms.

  • It tells us about the specific characteristics of an individual or group.
  • It helps in understanding their role in the ecosystem.
  • It is important in conservation, breeding, and agriculture.
  • It helps trace evolutionary history and relationships.
Q5. Given below is the scientific name of Mango. Identify the correctly written name.
Mangifera Indica
Mangifera indica
Answer - The correct scientific name is:

Mangifera indica

  • The first word (genus) starts with a capital letter.
  • The second word (species) starts with a small letter.
  • The full name is italicized or underlined when handwritten.
Q6. Define a taxon. Give some examples of taxa at different hierarchical levels.
Answer - A taxon is any group or category in a classification system used to group organisms.

Examples of taxa:
  • Species – Homo sapiens (humans)
  • Genus – Homo
  • Family – Felidae
  • Order – Primates
  • Class – Mammalia
  • Phylum – Chordata
  • Kingdom – Animalia
Q7. 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 - Let us compare the given sequences with the actual correct taxonomic hierarchy:

  • Species → Genus → Family → Order → Class → Phylum → Kingdom

Now examining the options:

(a) Species → Order → Phylum → Kingdom – Correct order, but skips Genus and Class
(b) Genus → Species → Order → Kingdom – Incorrect order; Species comes before Genus
(c) Species → Genus → Order → Phylum – Correct order, but skips Family and Class

Hence, both (a) and (c) follow the correct order of categories (despite skipping some), but option (c) is more accurate in the initial sequence.

Correct answer: (c)
Q8. 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.
Answer - ‘Species’ refers to a group of organisms that can interbreed and produce fertile offspring.

  • In higher plants and animals: Species have similar structure, behavior, and can reproduce among themselves.
  • In bacteria: Since they reproduce asexually, species are defined based on genetic similarity and biochemical properties.
  • Modern species concepts also consider evolutionary lineage and ecological roles.
Q9. Define and understand the following terms:
(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus
Answer -
  • Phylum: A group of related classes. Example: Chordata (includes animals with backbone)
  • Class: A group of related orders. Example: Mammalia
  • Family: A group of related genera. Example: Felidae (includes cats)
  • Order: A group of related families. Example: Carnivora
  • Genus: A group of related species. Example: Panthera (includes lion, tiger)
Q10. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.
Answer - Example of Animal (Tiger):

  • Kingdom – Animalia
  • Phylum – Chordata
  • Class – Mammalia
  • Order – Carnivora
  • Family – Felidae
  • Genus – Panthera
  • Species – Panthera tigris

Example of Plant (Mango):

  • Kingdom – Plantae
  • Phylum – Angiospermae
  • Class – Dicotyledonae
  • Order – Sapindales
  • Family – Anacardiaceae
  • Genus – Mangifera
  • Species – Mangifera indica