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Class 11 | CBSE | BIOLOGY
COMPLETE SOLUTIONS

NCERT Exercise – Chapter 1: The Living World (Class 11, CBSE)
Complete, exam-oriented answers, written strictly as per NCERT language, board patterns, and marking schemes.

1. Why are living organisms classified?

Answer:
Living organisms are classified to make the study of the vast diversity of life easy, systematic, and scientific. Classification helps in identifying organisms, understanding their relationships, avoiding confusion caused by local names, and predicting the characteristics of organisms based on their group.

2. Why are the classification systems changing every now and then?

Answer:
Classification systems keep changing due to continuous discovery of new organisms and advancement in scientific knowledge, especially in cytology, genetics, molecular biology, and evolutionary biology. New tools like DNA sequencing have improved our understanding of relationships among organisms, leading to modifications in classification.

3. What different criteria would you choose to classify people that you meet often?

Answer:
People can be classified based on various criteria such as:

• Age

• Gender

• Profession

• Physical features (height, complexion)

• Habits

• Language

• Educational background

Different criteria serve different purposes of classification.

4. What do we learn from identification of individuals and populations?

Answer:
Identification helps in recognizing individuals and populations correctly, studying their characteristics, understanding their distribution, evolutionary relationships, and role in the ecosystem. It also helps in conservation and scientific communication.

5. Given below is the scientific name of Mango. Identify the correctly written name.

❌ Mangifera Indica
✅ Mangifera indica

Explanation:

• Genus name starts with a capital letter

• Species name starts with a small letter

• Scientific names are written in italics or underlined separately when handwritten.

6. Define a taxon. Give some examples of taxa at different hierarchical levels.

Answer:
A taxon is a taxonomic group or category at any level of classification.

Examples:

• Kingdom → Plantae

• Phylum → Chordata

• Class → Mammalia

• Order → Primata

• Family → Hominidae

• Genus → Homo

• Species → Homo sapiens

7. Can you identify the correct sequence of taxonomical categories?

Correct answer:
(c) Species → Genus → Order → Phylum

Correct hierarchy:
Species → Genus → Family → Order → Class → Phylum → Kingdom

8. Try to collect all the currently accepted meanings for the word ‘species’. Discuss the meaning of species in higher plants and animals on one hand, and bacteria on the other hand.

Answer:

Species (General Definition):

A species is a group of organisms that can interbreed freely and produce fertile offspring.

In higher plants and animals:

Species are defined based on:

• Morphological similarity

• Reproductive isolation

• Genetic similarity

In bacteria:

Since bacteria reproduce asexually, species are defined based on:

• Genetic similarity

• Biochemical characteristics

• Physiological traits

Thus, the concept of species differs between sexually reproducing organisms and asexual organisms.

9. Define and understand the following terms:

(i) Phylum

A group of related classes having similar basic body plan.

(ii) Class

A group of related orders.

(iii) Family

A group of related genera sharing common characteristics.

(iv) Order

A group of related families.

(v) Genus

A group of closely related species.

10. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

Plant Example – Mango (Mangifera indica)

Category	Name
Kingdom	Plantae
Division	Angiospermae
Class	Dicotyledonae
Order	Sapindales
Family	Anacardiaceae
Genus	Mangifera
Species	indica

Animal Example – Human (Homo sapiens)

Category	Name
Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Primata
Family	Hominidae
Genus	Homo
Species	sapiens

Board Tip

For 5-mark questions, always:

• Draw a neat hierarchy table

• Write scientific names correctly

• Use proper sequence

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