Important Questions Class 11 Biology Chapter 2: Biological Classification With Answers

Biological classification is the scientific grouping of organisms based on shared characters and evolutionary relationships. Modern classification uses cell type, body organisation, nutrition, reproduction, and phylogeny as major criteria.

Classification gives order to biological diversity by grouping organisms through scientific criteria. Important Questions Class 11 Biology Chapter 2 test Whittaker’s five kingdom classification, Monera, Protista, Fungi, Plantae, Animalia, viruses, viroids, prions, and lichens. CBSE 2026 questions often focus on comparison tables, kingdom features, bacterial shapes, protistan groups, fungal classes, and NCERT exercise answers. The NCERT Reprint 2026-27 treats Plantae and Animalia briefly here and covers them in later chapters.

Key Takeaways

• R.H. Whittaker: Five kingdom classification was proposed in 1969.
• Kingdom Monera: Bacteria are the sole members of this kingdom.
• Kingdom Protista: All single-celled eukaryotes come under Protista.
• Kingdom Fungi: Fungal cell walls contain chitin and polysaccharides.

Important Questions Class 11 Biology Chapter 2 Structure 2026

Important Questions Class 11 Biology Chapter 2: Key Concepts

These class 11 biology chapter 2 important questions cover the main NCERT foundation. Learn the classification basis before moving to kingdoms.

Q1. What Is Biological Classification?

Biological classification is the scientific grouping of organisms based on shared features. It also reflects evolutionary relationships.

1. Main Basis:
   Cell structure, body organisation, nutrition, reproduction, and phylogeny.
2. Purpose:
   It helps organise biodiversity.
3. Final Result:
   Biological classification groups organisms scientifically

Q2. Why Was Two Kingdom Classification Found Inadequate?

Two kingdom classification was inadequate because it grouped very different organisms together. It ignored prokaryotes, unicellular organisms, and fungi.

1. Main Problem:
   It did not separate prokaryotes from eukaryotes.
2. Another Issue:
   It grouped fungi with plants.
3. Final Result:
   Two kingdom classification failed to reflect major biological differences

Q3. Who Proposed Five Kingdom Classification?

R.H. Whittaker proposed five kingdom classification in 1969. He classified organisms into Monera, Protista, Fungi, Plantae, and Animalia.

1. Scientist:
   R.H. Whittaker.
2. Year:
   1969.
3. Final Result:
   Whittaker proposed the five kingdom classification

Q4. What Criteria Did Whittaker Use For Classification?

Whittaker used cell structure, body organisation, mode of nutrition, reproduction, and phylogenetic relationships.

1. Cellular Criteria:
   Prokaryotic or eukaryotic.
2. Nutritional Criteria:
   Autotrophic or heterotrophic.
3. Final Result:
   Whittaker used multiple scientific criteria

Biological Classification Class 11 MCQ With Answers

These biological classification class 11 MCQ questions test NCERT facts and examples. They follow the CBSE 2026 board pattern.

Q1. Who Proposed The Five Kingdom Classification?

R.H. Whittaker proposed the five kingdom classification in 1969.

1. Options:
   (A) Aristotle
   (B) Linnaeus
   (C) R.H. Whittaker
   (D) T.O. Diener
2. Rule Used:
   Five kingdom classification belongs to Whittaker.
3. Final Result:
   Answer: (C) R.H. Whittaker

Q2. Which Kingdom Contains Only Prokaryotes?

Kingdom Monera contains prokaryotic organisms. Bacteria are its sole members.

1. Options:
   (A) Protista
   (B) Monera
   (C) Fungi
   (D) Animalia
2. Rule Used:
   Monera includes bacteria.
3. Final Result:
   Answer: (B) Monera

Q3. Which Organism Lacks A Cell Wall Completely?

Mycoplasma lacks a cell wall. It is the smallest known living cell.

1. Options:
   (A) Nostoc
   (B) Mycoplasma
   (C) Euglena
   (D) Puccinia
2. Rule Used:
   Mycoplasma completely lacks a cell wall.
3. Final Result:
   Answer: (B) Mycoplasma

Q4. Which Group Forms Diatomaceous Earth?

Diatoms form diatomaceous earth. Their silica walls leave large deposits.

1. Options:
   (A) Dinoflagellates
   (B) Diatoms
   (C) Euglenoids
   (D) Slime moulds
2. Rule Used:
   Diatom walls contain silica.
3. Final Result:
   Answer: (B) Diatoms

Q5. Which Protist Causes Malaria?

Plasmodium causes malaria. It belongs to sporozoans.

1. Options:
   (A) Amoeba
   (B) Paramoecium
   (C) Plasmodium
   (D) Euglena
2. Rule Used:
   Plasmodium is the malarial parasite.
3. Final Result:
   Answer: (C) Plasmodium

Q6. Which Fungus Produces Antibiotic Source?

Penicillium is a source of antibiotics. It belongs to Kingdom Fungi.

1. Options:
   (A) Penicillium
   (B) Nostoc
   (C) Gonyaulax
   (D) Chlamydomonas
2. Rule Used:
   Penicillium gives antibiotic source.
3. Final Result:
   Answer: (A) Penicillium

Q7. Which Fungus Causes Wheat Rust?

Puccinia causes wheat rust. It is an important basidiomycete example.

1. Options:
   (A) Mucor
   (B) Rhizopus
   (C) Puccinia
   (D) Neurospora
2. Rule Used:
   Puccinia causes rust disease.
3. Final Result:
   Answer: (C) Puccinia

Q8. Which Infectious Agent Lacks A Protein Coat?

Viroid lacks a protein coat. It contains free low molecular weight RNA.

1. Options:
   (A) Virus
   (B) Viroid
   (C) Prion
   (D) Lichen
2. Rule Used:
   Viroids are free RNA without capsid.
3. Final Result:
   Answer: (B) Viroid

Q9. Which Association Forms Lichens?

Lichens are symbiotic associations between algae and fungi.

1. Options:
   (A) Virus and bacterium
   (B) Alga and fungus
   (C) Fungus and protozoan
   (D) Bacterium and plant
2. Rule Used:
   Lichen has phycobiont and mycobiont.
3. Final Result:
   Answer: (B) Alga and fungus

Q10. Which Organism Causes Red Tides?

Gonyaulax can cause red tides. It is a red dinoflagellate.

1. Options:
   (A) Gonyaulax
   (B) Euglena
   (C) Amoeba
   (D) Mucor
2. Rule Used:
   Red dinoflagellates multiply rapidly.
3. Final Result:
   Answer: (A) Gonyaulax

Five Kingdom Classification Class 11 Important Questions

Five kingdom classification class 11 questions often test criteria and kingdom differences. The NCERT table gives the most important comparison points.

Q1. Name The Five Kingdoms In Whittaker Classification.

The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.

1. Prokaryotic Kingdom:
   Monera.
2. Eukaryotic Kingdoms:
   Protista, Fungi, Plantae, Animalia.
3. Final Result:
   Whittaker classified life into five kingdoms

Q2. What Is The Cell Type In Each Kingdom?

Monera is prokaryotic, while Protista, Fungi, Plantae, and Animalia are eukaryotic.

1. Prokaryotic:
   Monera.
2. Eukaryotic:
   Protista, Fungi, Plantae, Animalia.
3. Final Result:
   Only Monera has prokaryotic cell type

Q3. Which Kingdoms Have Cell Walls?

Monera, some Protista, Fungi, and Plantae have cell walls. Animalia lacks cell wall.

1. Fungi:
   Chitinous cell wall.
2. Plantae:
   Cellulosic cell wall.
3. Final Result:
   Animalia has no cell wall

Q4. How Does Mode Of Nutrition Differ In Five Kingdoms?

Monera and Protista may be autotrophic or heterotrophic. Fungi and Animalia are heterotrophic, while Plantae are autotrophic.

1. Autotrophic:
   Plantae.
2. Heterotrophic:
   Fungi and Animalia.
3. Mixed Modes:
   Monera and Protista.
4. Final Result:
   Nutrition helps separate the five kingdoms

Q5. Why Were Fungi Placed In A Separate Kingdom?

Fungi were placed separately because they are heterotrophic and have chitinous cell walls. Green plants are autotrophic with cellulosic walls.

1. Nutrition:
   Fungi are absorptive heterotrophs.
2. Wall Composition:
   Fungal wall contains chitin.
3. Final Result:
   Fungi differ from green plants in nutrition and wall composition

Kingdom Monera Class 11 Important Questions

Kingdom Monera class 11 important questions focus on bacteria, archaebacteria, eubacteria, cyanobacteria, and mycoplasma. Bacteria show major metabolic diversity.

Q1. Why Are Bacteria Placed In Kingdom Monera?

Bacteria are placed in Kingdom Monera because they are prokaryotic. They lack a true nucleus and nuclear membrane.

1. Cell Type:
   Prokaryotic.
2. Nuclear Membrane:
   Absent.
3. Final Result:
   Bacteria are sole members of Monera

Q2. What Are The Four Bacterial Shapes?

The four bacterial shapes are coccus, bacillus, vibrio, and spirillum.

1. Coccus:
   Spherical.
2. Bacillus:
   Rod-shaped.
3. Vibrio:
   Comma-shaped.
4. Spirillum:
   Spiral.
5. Final Result:
   Bacteria are grouped by shape

Q3. What Are Archaebacteria?

Archaebacteria are special bacteria that live in extreme habitats. Their different cell wall helps them survive harsh conditions.

1. Halophiles:
   Live in extreme salty areas.
2. Thermoacidophiles:
   Live in hot springs.
3. Methanogens:
   Live in marshy areas and ruminant gut.
4. Final Result:
   Archaebacteria survive extreme habitats

Q4. What Is The Role Of Methanogens?

Methanogens produce methane or biogas from dung of ruminant animals. They occur in cow and buffalo gut.

1. Habitat:
   Gut of ruminants.
2. Product:
   Methane.
3. Final Result:
   Methanogens help produce biogas

Q5. What Are Eubacteria?

Eubacteria are true bacteria with a rigid cell wall. Motile forms may have flagella.

1. Cell Wall:
   Rigid.
2. Motility:
   Flagellum may occur.
3. Final Result:
   Eubacteria are true bacteria

Q6. What Are Cyanobacteria?

Cyanobacteria are photosynthetic autotrophic bacteria with chlorophyll a. They are also called blue-green algae.

1. Examples:
   Nostoc and Anabaena.
2. Special Cells:
   Heterocysts fix atmospheric nitrogen.
3. Final Result:
   Cyanobacteria perform photosynthesis and nitrogen fixation

Q7. What Are Chemosynthetic Autotrophic Bacteria?

Chemosynthetic autotrophic bacteria oxidise inorganic substances and use released energy for ATP production.

1. Substances Oxidised:
   Nitrates, nitrites, ammonia.
2. Ecological Role:
   Nutrient recycling.
3. Final Result:
   Chemosynthetic bacteria recycle nutrients

Q8. What Are Heterotrophic Bacteria?

Heterotrophic bacteria depend on other organisms or dead organic matter for food. They are most abundant in nature.

1. Useful Roles:
   Curd formation, antibiotics, nitrogen fixation.
2. Harmful Roles:
   Cholera, typhoid, tetanus, citrus canker.
3. Final Result:
   Heterotrophic bacteria affect humans and ecosystems

Q9. What Is Mycoplasma?

Mycoplasma is the smallest known living cell. It lacks a cell wall and can survive without oxygen.

1. Cell Wall:
   Completely absent.
2. Nature:
   Many forms are pathogenic.
3. Final Result:
   Mycoplasma lacks cell wall

Kingdom Protista Class 11 Questions And Answers

Kingdom Protista class 11 questions cover single-celled eukaryotes. NCERT includes chrysophytes, dinoflagellates, euglenoids, slime moulds, and protozoans.

Q1. What Are The General Features Of Kingdom Protista?

Protista includes single-celled eukaryotes. Protists are mainly aquatic and have a well-defined nucleus.

1. Cell Type:
   Eukaryotic.
2. Habitat:
   Primarily aquatic.
3. Reproduction:
   Asexual and sexual.
4. Final Result:
   Protista links plants, animals, and fungi

Q2. What Are Chrysophytes?

Chrysophytes include diatoms and golden algae. They occur in freshwater and marine environments.

1. Mode Of Life:
   Microscopic plankton.
2. Nutrition:
   Mostly photosynthetic.
3. Final Result:
   Chrysophytes include diatoms and desmids

Q3. Why Are Diatom Walls Indestructible?

Diatom walls are indestructible because they contain silica. Their walls form two overlapping shells.

1. Wall Structure:
   Soap-box arrangement.
2. Deposit Formed:
   Diatomaceous earth.
3. Final Result:
   Silica makes diatom walls resistant

Q4. What Are Dinoflagellates?

Dinoflagellates are mostly marine photosynthetic protists. Their cell wall has stiff cellulose plates.

1. Flagella:
   Two flagella.
2. Pigments:
   Yellow, green, brown, blue, or red.
3. Final Result:
   Dinoflagellates can form red tides

Q5. What Are Euglenoids?

Euglenoids are freshwater protists found in stagnant water. They have a protein-rich pellicle instead of a cell wall.

1. Nutrition In Sunlight:
   Photosynthetic.
2. Nutrition Without Sunlight:
   Heterotrophic.
3. Final Result:
   Euglenoids show flexible nutrition

Q6. What Are Slime Moulds?

Slime moulds are saprophytic protists. They move over decaying leaves and twigs.

1. Suitable Conditions:
   Form plasmodium.
2. Unfavourable Conditions:
   Form fruiting bodies with resistant spores.
3. Final Result:
   Slime mould spores survive adverse conditions

Q7. What Are The Four Groups Of Protozoans?

The four groups are amoeboid, flagellated, ciliated, and sporozoan protozoans.

1. Amoeboid:
   Amoeba and Entamoeba.
2. Flagellated:
   Trypanosoma.
3. Ciliated:
   Paramoecium.
4. Sporozoan:
   Plasmodium.
5. Final Result:
   Protozoans are heterotrophic protists

Kingdom Fungi Class 11 Important Questions

Kingdom fungi class 11 important questions focus on fungal body structure, nutrition, reproduction, and classes. Fungi are heterotrophic and cosmopolitan.

Q1. What Are The General Features Of Kingdom Fungi?

Fungi are heterotrophic organisms with chitinous cell walls. Most fungi are filamentous and form mycelium.

1. Body Structure:
   Hyphae form mycelium.
2. Cell Wall:
   Chitin and polysaccharides.
3. Final Result:
   Fungi form a separate kingdom

Q2. What Are Hyphae And Mycelium?

Hyphae are long thread-like fungal structures. A network of hyphae forms mycelium.

1. Coenocytic Hyphae:
   Continuous tubes with multinucleated cytoplasm.
2. Septate Hyphae:
   Hyphae with cross walls.
3. Final Result:
   Mycelium forms the fungal body

Q3. What Are The Modes Of Nutrition In Fungi?

Fungi may be saprophytes, parasites, or symbionts. Most absorb soluble organic matter.

1. Saprophytes:
   Feed on dead substrates.
2. Parasites:
   Depend on living hosts.
3. Symbionts:
   Form lichens and mycorrhiza.
4. Final Result:
   Fungi show absorptive heterotrophic nutrition

Q4. What Are The Three Steps In Fungal Sexual Cycle?

The three steps are plasmogamy, karyogamy, and meiosis.

1. Plasmogamy:
   Fusion of protoplasm.
2. Karyogamy:
   Fusion of nuclei.
3. Meiosis:
   Zygote forms haploid spores.
4. Final Result:
   Fungal sexual cycle has three stages

Q5. What Is Dikaryophase?

Dikaryophase is the phase where two haploid nuclei remain in one cell. It occurs in ascomycetes and basidiomycetes.

1. Nuclear Condition:
   n + n.
2. Later Event:
   Nuclei fuse during karyogamy.
3. Final Result:
   Dikaryophase delays nuclear fusion

Q6. What Are Phycomycetes?

Phycomycetes have aseptate and coenocytic mycelium. They occur in aquatic habitats or damp places.

1. Asexual Spores:
   Zoospores or aplanospores.
2. Sexual Spore:
   Zygospore.
3. Examples:
   Mucor, Rhizopus, Albugo.
4. Final Result:
   Phycomycetes have coenocytic mycelium

Q7. What Are Ascomycetes?

Ascomycetes are sac-fungi. They have branched and septate mycelium.

1. Asexual Spores:
   Conidia on conidiophores.
2. Sexual Spores:
   Ascospores inside asci.
3. Examples:
   Aspergillus, Claviceps, Neurospora, yeast.
4. Final Result:
   Ascomycetes produce ascospores in asci

Q8. What Are Basidiomycetes?

Basidiomycetes include mushrooms, bracket fungi, puffballs, rusts, and smuts. They have branched septate mycelium.

1. Sexual Structure:
   Basidium.
2. Spores:
   Basidiospores.
3. Examples:
   Agaricus, Ustilago, Puccinia.
4. Final Result:
   Basidiomycetes produce basidiospores on basidia

Q9. What Are Deuteromycetes?

Deuteromycetes are imperfect fungi because only asexual or vegetative phases are known.

1. Asexual Spores:
   Conidia.
2. Mycelium:
   Septate and branched.
3. Examples:
   Alternaria, Colletotrichum, Trichoderma.
4. Final Result:
   Deuteromycetes reproduce by conidia

Viruses Viroids Prions And Lichens Class 11 Questions

Viruses viroids prions and lichens class 11 questions test acellular agents and symbiotic associations. NCERT keeps them outside Whittaker’s five kingdoms.

Q1. Why Were Viruses Not Placed In Five Kingdom Classification?

Viruses were not placed in five kingdom classification because they lack cellular structure. They remain inert outside host cells.

1. Cell Structure:
   Non-cellular.
2. Nature:
   Obligate parasites.
3. Final Result:
   Viruses are acellular infectious agents

Q2. What Is The Structure Of A Virus?

A virus is a nucleoprotein with genetic material and a protein coat. The protein coat is called capsid.

1. Genetic Material:
   Either DNA or RNA.
2. Capsid Subunits:
   Capsomeres.
3. Final Result:
   Viruses contain nucleic acid and capsid

Q3. What Is The Genetic Material Of Viruses?

Viruses contain either RNA or DNA, never both. Plant viruses usually have single-stranded RNA.

1. Plant Viruses:
   Usually single-stranded RNA.
2. Animal Viruses:
   RNA or double-stranded DNA.
3. Bacteriophages:
   Usually double-stranded DNA.
4. Final Result:
   No virus contains both RNA and DNA

Q4. How Are Viroids Different From Viruses?

Viroids are smaller than viruses and lack a protein coat. They contain low molecular weight free RNA.

1. Discoverer:
   T.O. Diener.
2. Disease:
   Potato spindle tuber disease.
3. Final Result:
   Viroids are free RNA without capsid

Q5. What Are Prions?

Prions are infectious agents made of abnormally folded protein. They cause certain neurological diseases.

1. Cattle Disease:
   Bovine spongiform encephalopathy.
2. Human Disease:
   Creutzfeldt-Jakob disease.
3. Final Result:
   Prions are infectious proteins

Q6. What Are Lichens?

Lichens are symbiotic associations between algae and fungi. The algal partner is phycobiont, and fungal partner is mycobiont.

1. Phycobiont:
   Autotrophic alga.
2. Mycobiont:
   Heterotrophic fungus.
3. Final Result:
   Lichens combine algae and fungi

Q7. Why Are Lichens Called Pollution Indicators?

Lichens are pollution indicators because they do not grow in polluted areas.

1. Indicator Role:
   Show clean air conditions.
2. Growth Condition:
   They prefer unpolluted habitats.
3. Final Result:
   Lichens indicate air quality

Biological Classification Class 11 NCERT Questions

These biological classification class 11 NCERT questions follow the exercise pattern. They are written for CBSE 2026 revision.

Q1. Discuss How Classification Systems Changed Over Time.

Classification systems changed from simple morphology to scientific and phylogenetic criteria.

1. Aristotle:
   Used simple morphological characters.
2. Linnaeus:
   Used two kingdoms, Plantae and Animalia.
3. Whittaker:
   Used five kingdoms with multiple criteria.
4. Final Result:
   Modern classification reflects evolutionary relationships

Q2. State Two Economically Important Uses Of Heterotrophic Bacteria.

Heterotrophic bacteria help in curd formation and antibiotic production. Some also fix nitrogen in legume roots.

1. Food Use:
   Convert milk into curd.
2. Medical Use:
   Help in antibiotic production.
3. Final Result:
   Heterotrophic bacteria have economic value

Q3. State Two Economically Important Uses Of Archaebacteria.

Methanogenic archaebacteria produce biogas and help ruminant digestion. They occur in cow and buffalo gut.

1. Biogas Production:
   Methane forms from dung.
2. Ruminant Role:
   Help digestion in gut.
3. Final Result:
   Methanogens support biogas formation

Q4. What Is The Nature Of Cell Walls In Diatoms?

Diatom cell walls contain silica. Their walls form two thin overlapping shells.

1. Structure:
   Soap-box-like fit.
2. Property:
   Indestructible.
3. Final Result:
   Diatom walls are siliceous

Q5. What Do Algal Bloom And Red Tide Signify?

Algal bloom means rapid growth of algae in water. Red tide means rapid multiplication of red dinoflagellates such as Gonyaulax.

1. Algal Bloom:
   Often seen in polluted water bodies.
2. Red Tide:
   Can kill fishes due to toxins.
3. Final Result:
   Rapid algal growth can disturb aquatic life

Q6. How Are Viroids Different From Viruses?

Viroids lack the protein coat found in viruses. They contain only free low molecular weight RNA.

1. Virus:
   Has nucleic acid and capsid.
2. Viroid:
   Has only RNA.
3. Final Result:
   Viroids are simpler than viruses

Q7. Describe The Four Major Groups Of Protozoa.

The four groups are amoeboid, flagellated, ciliated, and sporozoans.

1. Amoeboid Protozoans:
   Use pseudopodia.
2. Flagellated Protozoans:
   Use flagella.
3. Ciliated Protozoans:
   Use cilia.
4. Sporozoans:
   Have infectious spore-like stage.
5. Final Result:
   Protozoans are grouped by locomotion and life cycle

Q8. Which Plants Are Partially Heterotrophic?

Bladderwort, Venus fly trap, and Cuscuta are partially heterotrophic plants.

1. Insectivorous Plants:
   Bladderwort and Venus fly trap.
2. Parasitic Plant:
   Cuscuta.
3. Final Result:
   Some plants are partly heterotrophic

Q9. What Do Phycobiont And Mycobiont Mean?

Phycobiont means algal partner, and mycobiont means fungal partner in lichen.

1. Phycobiont:
   Prepares food.
2. Mycobiont:
   Provides shelter, minerals, and water.
3. Final Result:
   Lichen has algal and fungal partners

Q10. Give A Comparative Account Of Classes Of Fungi.

Fungal classes differ in mycelium, spores, and reproduction.

1. Phycomycetes:
   Coenocytic mycelium, zoospores or aplanospores, zygospores.
2. Ascomycetes:
   Septate mycelium, conidia, ascospores.
3. Basidiomycetes:
   Septate mycelium, basidiospores on basidia.
4. Deuteromycetes:
   Septate mycelium, conidia, no known sexual stage.
5. Final Result:
   Spore type helps classify fungi

Q11. What Are The Characteristic Features Of Euglenoids?

Euglenoids have pellicle, two flagella, and flexible nutrition. They act as photosynthetic organisms in sunlight.

1. Cell Wall:
   Absent.
2. Pellicle:
   Protein-rich and flexible.
3. Nutrition:
   Photosynthetic in sunlight, heterotrophic without sunlight.
4. Final Result:
   Euglenoids show plant-like and animal-like features

Q12. Give A Brief Account Of Viruses.

Viruses are non-cellular obligate parasites with DNA or RNA and a protein coat.

1. Protein Coat:
   Capsid made of capsomeres.
2. Genetic Material:
   Either DNA or RNA.
3. Diseases:
   Mumps, smallpox, herpes, influenza.
4. Final Result:
   Viruses replicate only inside host cells