Chapter 2: Biological Classification – Long Answer Type Questions

CBSE Class 11 Biology Long Answer Questions – Chapter 2: Biological Classification (NCERT Based)

Course Details

Course: CBSE Class 11 Biology
Syllabus: NCERT
Unit: Unit I – Diversity in Living World
Chapter: Chapter 2 – Biological Classification
CBSE Board Examination: Central Board of Secondary Education – Class 11 (School & Annual Examinations)

CBSE Class 11 Biology Chapter 2 Biological Classification – 20 Long Answer Questions with Answers (NCERT)

Section A: Five Kingdom Classification (Q1–Q5)

Q1. Explain the need for biological classification and its significance in biology.

Biological classification is essential to organize the vast diversity of living organisms into systematic groups. It simplifies the study of organisms by grouping them based on similarities and differences. Classification helps in proper identification, avoids confusion caused by local names, and enables effective scientific communication. It also reveals evolutionary relationships among organisms and helps predict characteristics of newly discovered species. Without classification, studying millions of organisms individually would be extremely difficult. Hence, classification forms the foundation of biological studies.

Q2. Describe the Five Kingdom Classification proposed by R.H. Whittaker.

R.H. Whittaker proposed the Five Kingdom Classification in 1969. He classified organisms into Monera, Protista, Fungi, Plantae, and Animalia. The classification was based on cell structure, body organisation, mode of nutrition, reproduction, and phylogenetic relationships. Prokaryotes were placed in Monera, unicellular eukaryotes in Protista, absorptive heterotrophs in Fungi, autotrophs in Plantae, and ingestive heterotrophs in Animalia. This system is more natural and evolutionary compared to earlier classifications.

Q3. Why is Whittaker’s Five Kingdom system considered an improvement over earlier systems?

Earlier classification systems were artificial and based on a few superficial characters. Whittaker’s system considered multiple criteria such as cellular organisation, nutrition, and evolutionary relationships. It clearly separated prokaryotes from eukaryotes and recognised fungi as a separate kingdom. This system reflects natural relationships among organisms, making it scientifically more accurate and widely accepted.

Q4. Explain the role of mode of nutrition as a basis of classification.

Mode of nutrition reflects the metabolic and ecological role of organisms. Autotrophs synthesise their own food, while heterotrophs depend on others. Absorptive nutrition is characteristic of fungi, ingestive nutrition of animals, and photosynthesis of plants. Using nutrition as a basis helps distinguish major kingdoms and understand energy flow in ecosystems.

Q5. State the limitations of the Five Kingdom Classification.

The Five Kingdom system does not clearly separate unicellular and multicellular eukaryotes in all cases. Viruses are excluded as they are acellular. Some organisms like slime moulds show characters of more than one kingdom, making classification difficult.

Section B: Kingdom Monera (Q6–Q9)

Q6. Describe the general characteristics of Kingdom Monera.

Kingdom Monera includes unicellular prokaryotic organisms lacking a true nucleus and membrane-bound organelles. Their cell wall is usually made of peptidoglycan. Monerans show diverse modes of nutrition, including autotrophic and heterotrophic. Reproduction occurs mainly by binary fission. They are ubiquitous and found in all habitats, including extreme environments.

Q7. Explain the modes of nutrition in bacteria.

Bacteria exhibit both autotrophic and heterotrophic nutrition. Autotrophic bacteria may be photosynthetic or chemosynthetic. Heterotrophic bacteria may be saprophytic, parasitic, or symbiotic. This diversity allows bacteria to play significant ecological roles such as decomposition and nutrient cycling.

Q8. Write a note on cyanobacteria and their importance.

Cyanobacteria are photosynthetic prokaryotes commonly called blue-green algae. They contain chlorophyll and fix atmospheric nitrogen. They improve soil fertility and are important primary producers in aquatic ecosystems.

Q9. Why is Mycoplasma considered unique among Monerans?

Mycoplasma is the smallest living cell and lacks a cell wall. Due to absence of a rigid wall, it shows pleomorphic shapes and resistance to antibiotics that target cell walls.

Section C: Kingdom Protista (Q10–Q12)

Q10. Describe the general characteristics of Kingdom Protista.

Protista includes unicellular eukaryotic organisms with a true nucleus and membrane-bound organelles. Most protists are aquatic and show diverse modes of nutrition and locomotion. They form an important link between plants, animals, and fungi.

Q11. Explain any two major groups of Protista.

Diatoms are photosynthetic protists with siliceous cell walls and form the base of aquatic food chains. Protozoans are heterotrophic and motile, including Amoeba and Paramecium.

Q12. State the ecological importance of protists.

Protists contribute to oxygen production, form the base of aquatic food webs, and help maintain ecological balance. Some also cause diseases.

Section D: Kingdom Fungi (Q13–Q15)

Q13. Describe the general characteristics of Kingdom Fungi.

Fungi are eukaryotic heterotrophs with chitinous cell walls. They show absorptive nutrition and reproduce by spores. The body consists of hyphae forming a mycelium.

Q14. Explain the modes of reproduction in fungi.

Fungi reproduce vegetatively, asexually by spores, and sexually through fusion of gametes. These methods ensure rapid spread and survival.

Q15. State the economic importance of fungi.

Fungi are used in food production, fermentation, antibiotic manufacture, and act as decomposers recycling nutrients in ecosystems.

Section E: Plantae and Animalia (Q16–Q17)

Q16. Describe the general characteristics of Kingdom Plantae.

Plantae includes multicellular autotrophs with chlorophyll and cellulose cell walls. They perform photosynthesis and act as primary producers in ecosystems.

Q17. Explain the major characteristics of Kingdom Animalia.

Animals are multicellular heterotrophs lacking cell walls. They show ingestive nutrition, complex body organisation, and usually exhibit locomotion.

Section F: Viruses, Viroids, and Lichens (Q18–Q20)

Q18. Write a detailed note on viruses.

Viruses are acellular entities composed of nucleic acid and a protein coat. They are obligate intracellular parasites and remain inert outside host cells.

Q19. What are viroids? How do they differ from viruses?

Viroids are infectious RNA molecules without protein coats. Unlike viruses, they infect plants and are simpler in structure.

Q20. Explain the structure and significance of lichens.

Lichens are symbiotic associations between algae and fungi. Algae provide food, while fungi offer protection. Lichens are indicators of air pollution.

Exam Relevance

✔ Strictly NCERT-aligned
✔ Ideal for 5-mark CBSE Class 11 questions
✔ Strong focus on comparison and classification
✔ Suitable for annual examinations and revisions