Welcome to Convex classes Jaiipur complete guide to Class 11th Biology Chapter 2 Question Answer– Biological Classification. This post provides NCERT-based question answers, covering all in-text and end-of-chapter questions, plus extra practice questions to help students master the topic and score high in exams.
Chapter Summary: Biological Classification
This chapter introduces the evolution of classification systems, from Aristotle’s early models to Whittaker’s Five-Kingdom system. It covers:
- Economic importance of microbes
- Need for classification
- Features of Monera, Protista, Fungi, Plantae, Animalia
- Viruses, Viroids, and Lichens
NCERT Textbook Questions with Answers | Class 11th Biology Chapter 2
Q1. Discuss how classification systems have undergone several changes over a period of time.
Ans: Classification systems evolved from Aristotle’s morphological traits to Linnaeus’s two-kingdom system. Whittaker’s five-kingdom system added cellular structure, nutrition, reproduction, and phylogeny. Later, the three-domain system further refined classification.
Q2. State two economically important uses of: (a) Heterotrophic bacteria (b) Archaebacteria
Ans: (a) Heterotrophic bacteria:
- Used in curd, cheese, and antibiotic production
- Help in nitrogen fixation and sewage treatment
(b) Archaebacteria:
- Produce biogas (methanogens)
- Used in bioleaching and cellulose fermentation
Q3. What is the nature of cell walls in diatoms?
Ans: Diatoms have cell walls made of silica, forming a two-part shell called a frustule, which is highly durable and patterned.
Q4. Find out what do the terms ‘algal bloom’ and ‘red tides’ signify.
Ans:
- Algal bloom: Rapid increase of algae in water due to nutrient enrichment
- Red tides: Discoloration of seawater caused by toxic algal blooms, often harmful to marine life
Q5. How are viroids different from viruses?
Ans:
- Viroids are smaller, consist only of RNA, and lack a protein coat
- Viruses have both nucleic acid (DNA or RNA) and a protein coat
Q6. Describe briefly the four major groups of Protozoa.
Ans:
- Amoeboid protozoa: Move using pseudopodia (e.g., Amoeba)
- Flagellated protozoa: Use flagella for movement (e.g., Trypanosoma)
- Ciliated protozoa: Use cilia (e.g., Paramecium)
- Sporozoa: Non-motile, parasitic (e.g., Plasmodium)
Q7. Plants are autotrophic. Can you think of some plants that are partially heterotrophic?
Ans:
- Insectivorous plants like Nepenthes (pitcher plant), Drosera, and Utricularia trap insects for nitrogen
- Parasitic plants like Cuscuta absorb nutrients from host plants
Q8. What do the terms phycobiont and mycobiont signify?
Ans:
- Phycobiont: Algal component of lichens
- Mycobiont: Fungal component of lichens Together, they form a symbiotic relationship.
Q9. Give a comparative account of the classes of Kingdom Fungi under the following: mode of nutrition, mode of reproduction, and examples.
| Class | Nutrition | Reproduction | Examples |
|---|---|---|---|
| Phycomycetes | Saprophytic/Parasitic | Asexual (zoospores), Sexual (isogamy) | Mucor, Rhizopus |
| Ascomycetes | Saprophytic/Parasitic | Asexual (conidia), Sexual (ascospores) | Yeast, Penicillium |
| Basidiomycetes | Saprophytic | Asexual (rare), Sexual (basidiospores) | Agaricus, Puccinia |
| Deuteromycetes | Mostly parasitic | Asexual (conidia), Sexual (unknown) | Alternaria, Colletotrichum |
Q10. What are the characteristic features of Euglenoids?
Ans:
- Found in freshwater
- Lack cell wall, have protein-rich pellicle
- Photosynthetic in sunlight, heterotrophic in dark
- Move using flagella
Q11. Give a brief account of viruses with respect to their structure and nature of genetic material. Also name four common viral diseases.
Ans:
- Structure: Core of DNA/RNA surrounded by a protein coat (capsid)
- Genetic Material: DNA or RNA (never both)
- Diseases: Influenza, HIV/AIDS, Hepatitis, Polio
Q12. Organise the organisms in Kingdom Monera and Protista based on their cell structure, mode of nutrition, and habitat.
| Kingdom | Cell Structure | Nutrition | Habitat |
|---|---|---|---|
| Monera | Prokaryotic | Auto/Heterotrophic | Soil, water, extreme environments |
| Protista | Eukaryotic | Auto/Heterotrophic | Freshwater, marine |
Q13. How has the advancement of microscopy helped our understanding of living organisms?
Ans: Microscopy revealed cellular structures, enabling classification based on cell type, organelles, and reproduction. It helped distinguish prokaryotes from eukaryotes and discover viruses, viroids, and prions.
Extra Practice Questions (With Answers)
Q1. Differentiate between Monera and Protista.
| Feature | Monera | Protista |
|---|---|---|
| Cell Type | Prokaryotic | Eukaryotic |
| Nucleus | Absent | Present |
| Examples | Bacteria | Amoeba, Paramecium |
Q2. Why are viruses not included in the five-kingdom classification?
Ans: Viruses are acellular and lack metabolic activity outside a host, hence they don’t fit into any kingdom.
Q3. What are lichens and why are they ecologically important?
Ans: Lichens are symbiotic associations between algae and fungi. They act as bioindicators and help in soil formation.
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