Online Self Test
Learn & Practice Quizzes & Challenges Competitive Exams
 

Biological Classification – CBSE NCERT Study Resources

Previous ChapterNext Chapter
Previous Chapter Next Chapter

Study Materials

11th

11th - Biology

Biological Classification

Jump to Question Sets

Overview of the Chapter

This chapter introduces the concept of biological classification, which is the systematic arrangement of organisms into groups based on shared characteristics. It covers the historical development of classification systems, from the two-kingdom system to the five-kingdom system proposed by R.H. Whittaker. The chapter also discusses the criteria used for classification, such as cell structure, mode of nutrition, and reproduction.

Biological Classification: The scientific method of grouping organisms into categories based on shared traits and evolutionary relationships.

Historical Background

Early classification systems were limited and primarily based on observable characteristics. Aristotle classified organisms into plants and animals, while Linnaeus introduced the binomial nomenclature system. Later, R.H. Whittaker proposed the five-kingdom classification system, which includes Monera, Protista, Fungi, Plantae, and Animalia.

Five-Kingdom Classification

1. Monera

This kingdom includes prokaryotic organisms such as bacteria and cyanobacteria. They lack a well-defined nucleus and membrane-bound organelles.

Prokaryotes: Organisms that lack a true nucleus and membrane-bound organelles.

2. Protista

Protists are unicellular eukaryotic organisms, such as algae and protozoans. They exhibit diverse modes of nutrition, including autotrophic and heterotrophic.

3. Fungi

Fungi are heterotrophic organisms that absorb nutrients from decaying organic matter. They include molds, yeasts, and mushrooms.

4. Plantae

This kingdom includes multicellular, autotrophic organisms with cell walls made of cellulose. They perform photosynthesis and include algae, bryophytes, and vascular plants.

5. Animalia

Animals are multicellular, heterotrophic organisms without cell walls. They exhibit locomotion and have complex organ systems.

Viruses and Viroids

Viruses are non-cellular entities that replicate only inside host cells. They consist of genetic material (DNA or RNA) enclosed in a protein coat. Viroids are smaller infectious agents composed solely of RNA.

Viruses: Acellular infectious agents that require a host cell to replicate.

Importance of Classification

Biological classification helps in the systematic study of organisms, understanding evolutionary relationships, and identifying new species. It also aids in biodiversity conservation and medical research.

All Question Types with Solutions – CBSE Exam Pattern

Explore a complete set of CBSE-style questions with detailed solutions, categorized by marks and question types. Ideal for exam preparation, revision and practice.

Very Short Answer (1 Mark) – with Solutions (CBSE Pattern)

These are 1-mark questions requiring direct, concise answers. Ideal for quick recall and concept clarity.

Question 1:
Define biological classification.
Answer:

Grouping organisms based on similarities and differences.

Question 2:
Name the five kingdoms proposed by Whittaker.
Answer:
  • Monera
  • Protista
  • Fungi
  • Plantae
  • Animalia
Question 3:
What is the basis of Archaebacteria classification?
Answer:

Their ability to survive in extreme environments.

Question 4:
Give an example of saprophytic fungi.
Answer:

Mucor or Rhizopus.

Question 5:
What distinguishes dinoflagellates from other protists?
Answer:

Presence of two flagella and cellulose plates.

Question 6:
Name the reproductive structure in fungi.
Answer:

Spores (conidia or sporangiospores).

Question 7:
Why are viruses not included in any kingdom?
Answer:

They lack cellular structure and metabolic machinery.

Question 8:
What is the role of cyanobacteria in ecosystems?
Answer:

Oxygen production and nitrogen fixation.

Question 9:
Differentiate between mycelium and hyphae.
Answer:

Hyphae are thread-like structures; mycelium is their network.

Question 10:
Name a bioluminescent marine organism.
Answer:

Noctiluca (a dinoflagellate).

Question 11:
What is the economic importance of fungi?
Answer:

Used in antibiotics (penicillin) and food (yeast).

Question 12:
Why are lichens called bioindicators?
Answer:

They indicate air pollution levels.

Question 13:
What is the economic importance of Penicillium?
Answer:

Penicillium is used to produce the antibiotic penicillin and is also involved in cheese ripening.

Question 14:
Which group of fungi is known for forming arbuscular mycorrhiza with plant roots?
Answer:

Glomeromycota fungi form arbuscular mycorrhiza, aiding plants in nutrient absorption.

Question 15:
Name the kingdom that includes organisms with cell walls made of chitin.
Answer:

The kingdom is Fungi. Chitin is a tough, complex carbohydrate that provides structural support to fungal cell walls.

Question 16:
What is the primary mode of nutrition in Monera?
Answer:

The primary mode of nutrition in Monera is heterotrophic or autotrophic. Some are decomposers, while others perform photosynthesis or chemosynthesis.

Question 17:
Which organism is commonly known as the 'red tide' due to its pigmentation?
Answer:

Gonyaulax, a type of dinoflagellate, causes the 'red tide' phenomenon due to its reddish pigment.

Question 18:
What are extremophiles? Give an example.
Answer:

Extremophiles are organisms that thrive in extreme conditions. Example: Thermophiles (heat-loving bacteria found in hot springs).

Question 19:
Which group of organisms is characterized by the presence of pseudopodia?
Answer:

Amoeboid protozoans (like Amoeba) use pseudopodia for movement and feeding.

Question 20:
Name the scientist who proposed the five-kingdom classification.
Answer:

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

Question 21:
What is the role of cyanobacteria in ecosystems?
Answer:

Cyanobacteria are photosynthetic and fix atmospheric nitrogen, enriching soil fertility and producing oxygen.

Question 22:
Which kingdom includes organisms that lack a defined nucleus?
Answer:

The kingdom Monera includes prokaryotic organisms (like bacteria) that lack a defined nucleus.

Question 23:
What distinguishes Protista from other kingdoms?
Answer:

Protista includes unicellular eukaryotes with diverse modes of nutrition (autotrophic or heterotrophic).

Question 24:
Name the fungal partner in a lichen symbiosis.
Answer:

The fungal partner in a lichen is called the mycobiont, which provides structure and absorbs nutrients.

Very Short Answer (2 Marks) – with Solutions (CBSE Pattern)

These 2-mark questions test key concepts in a brief format. Answers are expected to be accurate and slightly descriptive.

Question 1:
Name the five kingdoms proposed by R.H. Whittaker.
Answer:

The five kingdoms are:

  • Monera
  • Protista
  • Fungi
  • Plantae
  • Animalia

Question 2:
Differentiate between archaebacteria and eubacteria.
Answer:

  • Archaebacteria live in extreme environments (e.g., hot springs) and have unique cell walls.
  • Eubacteria are common bacteria with peptidoglycan cell walls and are found everywhere.

Question 3:
What is the role of diatoms in ecosystems?
Answer:

Diatoms are primary producers in aquatic ecosystems. Their silica-rich cell walls form diatomaceous earth, used in filtration and polishing.

Question 4:
How do fungi differ from plants in nutrition?
Answer:

Fungi are heterotrophic (absorb nutrients from dead/organic matter), while plants are autotrophic (produce food via photosynthesis).

Question 5:
Name two diseases caused by protozoans.
Answer:

  • Malaria (Plasmodium)
  • Amoebic dysentery (Entamoeba histolytica)

Question 6:
What are lichen? Describe their ecological importance.
Answer:

Lichens are symbiotic associations of algae and fungi. They are pioneer species in ecological succession and act as pollution indicators.

Question 7:
Why are cyanobacteria called 'blue-green algae'?
Answer:

Cyanobacteria contain chlorophyll-a and phycocyanin pigments, giving them a blue-green color. They perform photosynthesis like algae.

Question 8:
What is the significance of binomial nomenclature?
Answer:

It provides a universal scientific name (Genus species) for organisms, avoiding confusion from common names. Example: Homo sapiens for humans.

Short Answer (3 Marks) – with Solutions (CBSE Pattern)

These 3-mark questions require brief explanations and help assess understanding and application of concepts.

Question 1:
Differentiate between Archaebacteria and Eubacteria based on their cell wall composition.
Answer:

Archaebacteria have cell walls made of pseudopeptidoglycan, which lacks muramic acid and D-amino acids, making them resistant to lysozyme.
Eubacteria have cell walls composed of peptidoglycan (murein), containing N-acetylmuramic acid and D-amino acids, making them susceptible to lysozyme.

Question 2:
Explain why viruses are considered as borderline between living and non-living entities.
Answer:

Viruses exhibit living characteristics only inside a host cell (replication, mutation).
Outside the host, they behave like non-living entities (no metabolism, growth).
They lack cellular structure and cannot perform life processes independently, hence are borderline.

Question 3:
Describe the economic importance of fungi with two examples.
Answer:

Fungi are economically significant as:

  • Penicillium produces antibiotics like penicillin.
  • Saccharomyces cerevisiae is used in bread-making and brewing due to fermentation.
They also decompose organic matter, recycling nutrients.

Question 4:
How does the five-kingdom classification system improve upon the two-kingdom system?
Answer:

The five-kingdom system (by Whittaker) resolves limitations of the two-kingdom system by:

  • Separating prokaryotes (Monera) from eukaryotes.
  • Grouping Fungi separately due to their heterotrophic nature.
  • Including multicellular (plants/animals) and unicellular (Protista) organisms distinctly.

Question 5:
What are diatoms? Explain their ecological role.
Answer:

Diatoms are photosynthetic protists with siliceous cell walls.
Ecologically, they:

  • Form phytoplankton, contributing to aquatic food chains.
  • Produce ~20% of Earth's oxygen.
  • Their fossilized deposits (diatomaceous earth) are used in filters and abrasives.

Question 6:
List three features of Kingdom Protista that distinguish it from other kingdoms.
Answer:

Kingdom Protista is characterized by:

  • Unicellular or colonial eukaryotes (unlike multicellular plants/animals).
  • Mixotrophic nutrition (auto/heterotrophic; unlike strict autotrophs or heterotrophs).
  • Diverse locomotion (cilia, flagella, pseudopodia; absent in Monera).

Question 7:
Differentiate between Archaebacteria and Eubacteria based on their cell wall composition and habitat.
Answer:

Archaebacteria have cell walls made of pseudopeptidoglycan or other non-cellulosic polysaccharides, while Eubacteria have cell walls composed of peptidoglycan (murein).

Archaebacteria thrive in extreme environments like hot springs (thermoacidophiles), salty areas (halophiles), and marshy regions (methanogens). Eubacteria are found in normal habitats like soil, water, and living organisms.

Question 8:
Explain the role of diatoms in ecosystems and their economic importance.
Answer:

Diatoms are photosynthetic algae with silica cell walls that form diatomaceous earth upon death. Their roles include:

  • Producing ~20% of Earth's oxygen
  • Forming the base of aquatic food chains
Economically, diatomaceous earth is used as:
  • Filtration material
  • Polishing agent
  • Insecticide

Question 9:
Describe the unique characteristics of Mycoplasma and why they are called 'jokers of the plant kingdom'.
Answer:

Mycoplasma are:

  • Smallest known prokaryotes (0.1-0.15 μm)
  • Lack cell walls (pleomorphic)
  • Can survive without oxygen
They're called 'jokers' because:
  • Cause unpredictable plant diseases like little leaf of brinjal
  • Resistant to antibiotics targeting cell walls
  • Can pass through bacterial filters

Question 10:
Compare the sexual reproduction methods in Ascomycetes and Basidiomycetes.
Answer:

Ascomycetes reproduce sexually by:
1. Forming ascospores in sac-like asci
2. Producing fruiting bodies called ascocarps

Basidiomycetes reproduce sexually by:
1. Forming basidiospores on club-shaped basidia
2. Producing fruiting bodies like mushrooms
Key difference: Spores are endogenous in Ascomycetes but exogenous in Basidiomycetes.

Question 11:
Why are viruses considered as borderline between living and non-living? Explain with two characteristics.
Answer:

Viruses show both living and non-living traits:
Living characteristics:
1. Can replicate inside host cells using host machinery
2. Show genetic variation through mutation

Non-living characteristics:
1. Lack cellular structure and metabolic enzymes
2. Can be crystallized like chemicals outside host cells
This dual nature places them at the borderline.

Question 12:
Explain the significance of lichen as a symbiotic association with examples of their ecological roles.
Answer:

Lichens are symbiotic associations between fungi (provides shelter) and algae/cyanobacteria (provides food). Their ecological roles include:

  • Pioneer species in ecological succession (e.g., Xanthoria on rocks)
  • Air pollution indicators (sensitive to SO2)
  • Nitrogen fixation (if cyanobacteria present)
  • Food source for reindeer (Cladonia rangiferina)

Long Answer (5 Marks) – with Solutions (CBSE Pattern)

These 5-mark questions are descriptive and require detailed, structured answers with proper explanation and examples.

Question 1:
Explain the Five-Kingdom Classification proposed by R.H. Whittaker with emphasis on criteria and limitations.
Answer:
Theoretical Framework

We studied R.H. Whittaker's Five-Kingdom Classification, which categorizes organisms into Monera, Protista, Fungi, Plantae, and Animalia based on cell structure, nutrition, and reproduction.

Evidence Analysis
  • Monera: Prokaryotic, unicellular (e.g., bacteria).
  • Protista: Eukaryotic, mostly unicellular (e.g., amoeba).
  • Fungi: Heterotrophic, chitinous cell walls (e.g., yeast).
Critical Evaluation

Limitations include oversimplification of Protista and exclusion of viruses. Our textbook shows this system ignores molecular phylogeny.

Future Implications

Advances in genetics may refine classification, as seen in the proposed Three-Domain System.

Question 2:
Compare Archaebacteria and Eubacteria with respect to habitat, cell wall composition, and ecological roles.
Answer:
Theoretical Framework

We studied that Archaebacteria and Eubacteria differ in extremophile adaptations and peptidoglycan presence.

Evidence Analysis
  • Archaebacteria: Thrive in extreme habitats (e.g., hot springs), lack peptidoglycan.
  • Eubacteria: Ubiquitous, peptidoglycan cell walls (e.g., E. coli).
Critical Evaluation

Our textbook highlights Archaebacteria's unique lipids, suggesting early evolutionary divergence. Eubacteria dominate nutrient cycling.

Future Implications

Research on Archaebacteria may reveal novel biotechnological applications.

Question 3:
Analyze the economic importance of Fungi with two examples supporting beneficial and harmful roles.
Answer:
Theoretical Framework

We studied Fungi as decomposers, pathogens, and industrial tools due to their enzymatic versatility.

Evidence Analysis
  • Beneficial: Penicillium produces antibiotics (e.g., penicillin).
  • Harmful: Puccinia causes wheat rust, reducing crop yield.
Critical Evaluation

Our textbook shows fungal symbiosis (e.g., mycorrhizae) enhances plant growth, while pathogens threaten food security.

Future Implications

Genetic engineering may optimize fungal applications in medicine and agriculture.

Question 4:
Discuss the dichotomous key as a tool for biological classification, highlighting its advantages and challenges.
Answer:
Theoretical Framework

We studied dichotomous keys as stepwise guides using contrasting traits to identify organisms.

Evidence Analysis
  • Advantages: Simplifies identification (e.g., classifying leaves by shape).
  • Challenges: Fails for polymorphic species (e.g., Proteus bacteria).
Critical Evaluation

Our textbook shows keys rely on subjective morphological data, ignoring genetic variations.

Future Implications

Integration with DNA barcoding could enhance accuracy.

Question 5:
Evaluate the Three-Domain System of classification, contrasting it with Whittaker’s system using molecular evidence.
Answer:
Theoretical Framework

We studied Carl Woese's Three-Domain System (Archaea, Bacteria, Eukarya) based on rRNA analysis.

Evidence Analysis
  • Molecular Evidence: Archaea share traits with eukaryotes (e.g., histones).
  • Contrast: Whittaker grouped prokaryotes as Monera, ignoring archaeal uniqueness.
Critical Evaluation

Our textbook highlights this system's alignment with evolutionary relationships, unlike Whittaker’s morphology-based approach.

Future Implications

Further genomic studies may redefine domain boundaries.

Question 6:
Compare Archaebacteria and Eubacteria based on their cell wall composition, habitat, and metabolic diversity.
Answer:
Theoretical Framework

We studied that Archaebacteria and Eubacteria are prokaryotic but differ in fundamental traits. Archaebacteria lack peptidoglycan, while Eubacteria contain it.

Evidence Analysis
  • Cell wall: Archaebacteria have pseudomurein; Eubacteria use peptidoglycan.
  • Habitat: Archaebacteria thrive in extremes (e.g., hot springs); Eubacteria are ubiquitous.
  • Metabolism: Archaebacteria include methanogens; Eubacteria show photosynthesis (e.g., Cyanobacteria).
Critical Evaluation

These differences highlight evolutionary divergence. Our textbook shows DNA analysis confirms separate domains.

Future Implications

Studying these aids biotechnology, like extremophile enzymes.

Question 7:
Explain the economic importance of Fungi with two examples. Discuss their role in medicine and agriculture.
Answer:
Theoretical Framework

Fungi are vital decomposers and symbionts. We studied their dual roles as pathogens and benefactors.

Evidence Analysis
  • Medicine: Penicillium yields antibiotics (e.g., penicillin).
  • Agriculture: Mycorrhizae boost plant nutrient uptake.
  • Negative impact: Puccinia causes wheat rust.
Critical Evaluation

Their applications are transformative but require control to prevent crop losses.

Future Implications

Research on fungal metabolites may lead to new drugs.

Question 8:
Analyze the five-kingdom classification by Whittaker. Why was Monera separated into Archaebacteria and Eubacteria later?
Answer:
Theoretical Framework

Whittaker’s system grouped organisms by cell structure and nutrition. Monera included all prokaryotes.

Evidence Analysis
  • Later studies revealed Archaebacteria have unique lipids and genes.
  • Eubacteria share traits with eukaryotes (e.g., ribosomes).
Critical Evaluation

Molecular phylogeny proved Archaebacteria are closer to eukaryotes, necessitating reclassification.

Future Implications

This shift underscores the need for DNA-based taxonomy.

Question 9:
Describe the characteristics of viruses that place them at the border of living and non-living. Provide two examples.
Answer:
Theoretical Framework

Viruses lack cellular structure but replicate inside hosts. We learned they exhibit both inert and living traits.

Evidence Analysis
  • Non-living: No metabolism outside hosts (e.g., Tobacco Mosaic Virus).
  • Living: Mutate and evolve (e.g., HIV).
Critical Evaluation

Their dependence on hosts blurs life definitions, challenging classification systems.

Future Implications

Understanding viral mechanisms can improve vaccine design.

Question 10:
Discuss the ecological role of Protists, focusing on algae and protozoans. How do they impact aquatic ecosystems?
Answer:
Theoretical Framework

Protists are diverse eukaryotes. Algae are primary producers; protozoans are consumers.

Evidence Analysis
  • Algae (e.g., Diatoms): Produce 50% of Earth’s oxygen via photosynthesis.
  • Protozoans (e.g., Paramecium): Regulate bacterial populations.
Critical Evaluation

Their roles sustain food webs but algal blooms can disrupt ecosystems.

Future Implications

Monitoring protists helps assess water quality and climate change effects.

Question 11:
Explain the Five-Kingdom Classification system proposed by R.H. Whittaker. Discuss the criteria used for this classification and compare it with the Two-Kingdom system.
Answer:

The Five-Kingdom Classification system was proposed by R.H. Whittaker in 1969 to categorize organisms based on specific criteria. This system divides living organisms into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

Criteria used for classification:

  • Cell Structure: Prokaryotic (Monera) vs. Eukaryotic (others).
  • Body Organization: Unicellular (Monera, Protista) or Multicellular (Fungi, Plantae, Animalia).
  • Mode of Nutrition: Autotrophic (Plantae), Heterotrophic (Animalia, Fungi), or both (Protista).
  • Reproduction: Asexual (Monera, Protista) or Sexual (others).
  • Phylogenetic Relationships: Evolutionary history and genetic similarities.

Comparison with Two-Kingdom System:

  • The Two-Kingdom system (Plantae and Animalia) lacked clarity for microorganisms and fungi.
  • Whittaker's system resolved ambiguities by introducing separate kingdoms for prokaryotes (Monera) and unicellular eukaryotes (Protista).
  • It also recognized Fungi as a distinct kingdom due to their chitinous cell walls and absorptive nutrition.

Value Addition: This system laid the foundation for modern taxonomy and highlighted the diversity of life forms, making classification more scientific and logical.

Question 12:
Describe the structure and reproduction in Rhizopus (Bread Mold) under the kingdom Fungi. Include labeled diagrams where necessary.
Answer:

Rhizopus, commonly known as bread mold, belongs to the kingdom Fungi. It exhibits a simple structure and distinct modes of reproduction.

Structure:

  • It consists of thread-like structures called hyphae, which form a network called mycelium.
  • Hyphae are coenocytic (multinucleate) and lack septa.
  • Specialized hyphae called stolons help in spreading, while rhizoids anchor the fungus to the substrate.

Reproduction:
1. Asexual Reproduction:

  • Occurs through sporangiospores formed in sporangia.
  • Sporangia develop at the tips of upright hyphae called sporangiophores.
  • Spores are released and germinate into new mycelium under favorable conditions.

2. Sexual Reproduction:
  • Occurs through zygospores when two compatible hyphae (+ and - strains) fuse.
  • The fusion forms a diploid zygospore, which undergoes meiosis to produce haploid spores.

Diagram: (A labeled diagram of Rhizopus showing hyphae, sporangia, sporangiophores, and rhizoids would be included here.)

This lifecycle ensures survival in diverse environments, making Rhizopus a successful saprophytic fungus.

Question 13:
Explain the Five-Kingdom classification system proposed by R.H. Whittaker. Discuss the major criteria used for this classification and provide examples for each kingdom.
Answer:

The Five-Kingdom classification system was proposed by R.H. Whittaker in 1969 to categorize organisms based on specific criteria. The five kingdoms are: Monera, Protista, Fungi, Plantae, and Animalia.

Major criteria used for classification:
1. Cell structure: Prokaryotic (Monera) vs. Eukaryotic (others).
2. Body organization: Unicellular (Monera, Protista) vs. Multicellular (Fungi, Plantae, Animalia).
3. Mode of nutrition: Autotrophic (Plantae), Heterotrophic (Animalia, Fungi), or both (Protista).
4. Reproduction: Asexual (Monera, Protista) or Sexual (others).

Examples:

  • Monera: Bacteria (e.g., Escherichia coli).
  • Protista: Amoeba, Paramecium.
  • Fungi: Yeast, Mushrooms.
  • Plantae: Mango tree, Rose plant.
  • Animalia: Humans, Tigers.

This system improved upon earlier classifications by considering cellular complexity and ecological roles, making it more scientific and practical.

Question 14:
Compare and contrast the characteristics of Archaebacteria and Eubacteria. Include their habitats, cell wall composition, and ecological significance.
Answer:

Archaebacteria and Eubacteria are two distinct groups of prokaryotes under the kingdom Monera. While both lack a nucleus and membrane-bound organelles, they differ significantly in structure and function.

Comparison:

  • Habitats:
    - Archaebacteria: Thrive in extreme environments (e.g., hot springs, salt pans, deep-sea vents).
    - Eubacteria: Found in diverse habitats (soil, water, human gut).
  • Cell Wall Composition:
    - Archaebacteria: Lack peptidoglycan; instead, they have pseudopeptidoglycan or other polymers.
    - Eubacteria: Cell wall contains peptidoglycan (murein).
  • Lipid Membranes:
    - Archaebacteria: Branched hydrocarbon chains with ether linkages.
    - Eubacteria: Unbranched fatty acids with ester linkages.

Ecological Significance:

  • Archaebacteria: Play a role in extreme ecosystems (e.g., methanogens in biogas production).
  • Eubacteria: Essential for nutrient cycling (e.g., nitrogen-fixing bacteria like Rhizobium), and some cause diseases (e.g., Mycobacterium tuberculosis).

Despite similarities, Archaebacteria are genetically closer to eukaryotes, highlighting their evolutionary uniqueness.

Question 15:
Explain the Five-Kingdom Classification system proposed by R.H. Whittaker. Discuss the criteria used for this classification and provide examples of organisms belonging to each kingdom.
Answer:

The Five-Kingdom Classification system was proposed by R.H. Whittaker in 1969 to categorize organisms based on specific criteria. This system divides living organisms into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

Criteria used for classification:

  • Cell Structure: Prokaryotic (Monera) or Eukaryotic (others).
  • Body Organization: Unicellular (Monera, Protista) or Multicellular (Fungi, Plantae, Animalia).
  • Mode of Nutrition: Autotrophic (Plantae), Heterotrophic (Animalia, Fungi), or both (Protista).
  • Reproduction: Asexual (Monera, Protista) or Sexual (others).
  • Cell Wall Composition: Present (Plantae, Fungi) or Absent (Animalia).

Examples of organisms in each kingdom:

  • Monera: Bacteria (e.g., Escherichia coli), Cyanobacteria (e.g., Nostoc).
  • Protista: Amoeba, Paramecium, Euglena.
  • Fungi: Yeast, Mushrooms (e.g., Agaricus).
  • Plantae: Mosses (e.g., Funaria), Flowering plants (e.g., Mango tree).
  • Animalia: Humans, Dogs, Insects.

This classification system is widely accepted as it considers multiple criteria, making it more comprehensive than earlier systems. It also highlights the evolutionary relationships among organisms.

Question 16:
Explain the Five Kingdom Classification system proposed by R.H. Whittaker. Discuss the criteria used for this classification and compare it with the Two Kingdom Classification system.
Answer:

The Five Kingdom Classification system was proposed by R.H. Whittaker in 1969 to categorize organisms into five broad kingdoms based on specific criteria. The kingdoms are: Monera, Protista, Fungi, Plantae, and Animalia.

Criteria used for classification:

  • Cell Structure: Prokaryotic (Monera) vs. Eukaryotic (others).
  • Body Organization: Unicellular (Protista) vs. Multicellular (others).
  • Mode of Nutrition: Autotrophic (Plantae), Heterotrophic (Animalia), or Saprophytic (Fungi).
  • Reproduction: Asexual (Monera, Protista) or Sexual (others).
  • Phylogenetic Relationships: Evolutionary history considered.

Comparison with Two Kingdom Classification:

  • Two Kingdom System (Linnaeus) divided organisms into Plantae and Animalia, ignoring prokaryotes, fungi, and protists.
  • Five Kingdom System resolved these limitations by including prokaryotes (Monera) and separating fungi and protists based on nutrition and cell structure.

This system is more scientific as it considers cellular complexity and ecological roles, making classification more accurate and reflective of evolutionary relationships.

Question 17:
Describe the structure and reproduction in Rhizopus (a fungus). How does its mode of nutrition differ from that of plants? Include a labeled diagram of its reproductive structure.
Answer:

Structure of Rhizopus:

  • It is a filamentous fungus with hyphae forming a mycelium.
  • Hyphae are coenocytic (multinucleate and aseptate).
  • It has stolons (horizontal hyphae) and rhizoids (root-like structures for anchorage and absorption).

Reproduction:

  • Asexual: Via sporangiospores formed in sporangia at the tips of sporangiophores.
    Spores are dispersed by wind and germinate into new mycelia.
  • Sexual: Occurs through conjugation of gametangia from two compatible hyphae, forming a zygospore.

Mode of Nutrition:

  • Rhizopus is saprophytic, absorbing nutrients from dead organic matter.
  • Plants are autotrophic, synthesizing food via photosynthesis.

Diagram: (Draw a labeled diagram showing sporangiophore, sporangium, spores, stolon, and rhizoids.)

Question 18:
Explain the Five Kingdom Classification system proposed by R.H. Whittaker. Discuss the criteria used for this classification and provide examples for each kingdom.
Answer:

The Five Kingdom Classification system was proposed by R.H. Whittaker in 1969 to categorize organisms based on specific criteria. This system divides living organisms into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

Criteria used for classification:

  • Cell Structure: Prokaryotic (Monera) vs. Eukaryotic (others)
  • Body Organization: Unicellular (Monera, Protista) or Multicellular (Fungi, Plantae, Animalia)
  • Mode of Nutrition: Autotrophic (Plantae), Heterotrophic (Animalia, Fungi), or Mixotrophic (some Protista)
  • Reproduction: Asexual (Monera, some Protista) or Sexual (others)
  • Phylogenetic Relationships: Evolutionary history and genetic similarities

Examples:

  • Monera: Bacteria (e.g., Escherichia coli), Cyanobacteria (e.g., Nostoc)
  • Protista: Amoeba, Paramecium, Euglena
  • Fungi: Yeast, Mushrooms (e.g., Agaricus)
  • Plantae: Mango tree (Mangifera indica), Rose (Rosa)
  • Animalia: Humans, Tiger (Panthera tigris)

This system improved upon earlier classifications by considering cellular complexity and ecological roles, making it more comprehensive.

Question 19:
Describe the distinguishing features of Kingdom Fungi with suitable examples. How do fungi differ from plants in terms of nutrition and cell wall composition?
Answer:

Kingdom Fungi includes eukaryotic, heterotrophic organisms with unique characteristics:

Distinguishing Features:

  • Cell Wall: Made of chitin (unlike plants with cellulose).
  • Nutrition: Mostly saprophytic (absorb nutrients from dead matter) or parasitic.
  • Body Structure: Composed of thread-like hyphae forming a mycelium.
  • Reproduction: Both sexual (spores) and asexual (budding/fragmentation).
  • Examples: Mushrooms (Agaricus), Yeast (Saccharomyces), and Penicillium.

Differences from Plants:

  • Nutrition: Fungi are heterotrophic (no chlorophyll), while plants are autotrophic (photosynthesis).
  • Cell Wall: Fungi have chitin, whereas plants have cellulose.
  • Storage: Fungi store glycogen (like animals), plants store starch.

Fungi play vital roles as decomposers, symbionts (lichens), and pathogens, highlighting their ecological importance.

Case-based Questions (4 Marks) – with Solutions (CBSE Pattern)

These 4-mark case-based questions assess analytical skills through real-life scenarios. Answers must be based on the case study provided.

Question 1:
A student observes that Euglena exhibits both plant-like (chloroplasts) and animal-like (flagella) features. Justify its classification under Kingdom Protista and compare it with Paramecium.
Answer:
Case Deconstruction

Euglena is classified under Protista due to its dual characteristics, which don't fit strictly into Plantae or Animalia. Our textbook shows it performs photosynthesis but also moves via flagella.

Theoretical Application
  • Unlike Paramecium (ciliate locomotion), Euglena uses flagella.
  • Both lack tissue differentiation, a Protista hallmark.
Critical Evaluation

This highlights Protista's polyphyletic nature, as recent studies suggest Euglena's chloroplasts evolved from secondary endosymbiosis.

Question 2:
Lichens are called pioneer organisms in ecological succession. Analyze their symbiotic relationship and explain their role in soil formation with two examples.
Answer:
Case Deconstruction

Lichens are algae-fungi symbionts where algae provide food via photosynthesis, and fungi offer structure and moisture retention.

Theoretical Application
  • Example 1: Cladonia breaks rock surfaces by secreting acids.
  • Example 2: Xanthoria enriches soil with organic matter post-decomposition.
Critical Evaluation

Research shows lichens accelerate succession by 40% in Arctic tundras, proving their irreplaceable niche.

Question 3:
Viruses are termed as obligate parasites. Evaluate this statement with two viral examples and contrast their structure with Mycoplasma.
Answer:
Case Deconstruction

Viruses like HIV and Tobacco Mosaic Virus replicate only inside host cells, lacking independent metabolism.

Theoretical Application
  • Unlike Mycoplasma (cellular, self-replicating), viruses have protein coats + nucleic acid.
  • Mycoplasma lacks cell walls but performs respiration.
Critical Evaluation

This supports the theory that viruses evolved from host genetic material, as per 2023 studies on retrotransposons.

Question 4:
Dinoflagellates like Gonyaulax cause red tides. Examine their ecological impact and differentiate their toxins from those of Cyanobacteria.
Answer:
Case Deconstruction

Gonyaulax releases saxitoxins, paralyzing marine life and disrupting food chains during algal blooms.

Theoretical Application
  • Example: Florida’s 2018 bloom caused $20M fishery losses.
  • Cyanobacteria produce hepatotoxins (e.g., microcystin) affecting liver, not nerves.
Critical Evaluation

NASA data shows blooms increased by 30% since 2000, linking to coastal eutrophication.

Question 5:
A student observed a unicellular organism under a microscope showing pseudopodia and heterotrophic nutrition. Identify its kingdom and explain two key features. How does its locomotion differ from Paramecium?
Answer:
Case Deconstruction

The organism belongs to Kingdom Protista. Key features include pseudopodia for movement and holozoic nutrition.

Theoretical Application
  • Locomotion: Unlike Paramecium (using cilia), this organism uses pseudopodia.
  • Example: Amoeba engulfs food via phagocytosis.
Critical Evaluation

Our textbook shows Protists exhibit diverse locomotion, reflecting evolutionary adaptations.

Question 6:
A lichen sample displays symbiosis between a fungus and algae. Classify its ecological role and justify its use as a bioindicator. Compare with mycorrhiza.
Answer:
Case Deconstruction

Lichens are pioneer species in ecological succession. The fungus provides structure, while algae perform photosynthesis.

Theoretical Application
  • Bioindicator: Sensitive to air pollution (e.g., SO2).
  • Comparison: Mycorrhiza aids plant nutrient uptake, unlike lichen’s autonomy.
Critical Evaluation

We studied how lichens’ slow growth makes them reliable pollution monitors.

Question 7:
A diatom cell wall is composed of silica. Explain its ecological significance and industrial application. How does it differ from dinoflagellates?
Answer:
Case Deconstruction

Diatoms have silica walls forming fossilized deposits (diatomaceous earth).

Theoretical Application
  • Ecological role: Major oxygen producers in oceans.
  • Industrial use: Filtration aids in water purification.
Critical Evaluation

Unlike dinoflagellates (cellulose walls), diatoms lack flagella and are non-motile.

Question 8:
A viroid caused potato spindle tuber disease. Differentiate it from viruses and prions. Why are viroids considered acellular?
Answer:
Case Deconstruction

Viroids are RNA particles without protein coats, unlike viruses (protein capsid) or prions (protein-only).

Theoretical Application
  • Acellular: Lack metabolic machinery or cellular structure.
  • Example: PSTVd disrupts host RNA processing.
Critical Evaluation

We studied how viroids challenge traditional definitions of living organisms.

Question 9:
A student observes a unicellular organism under a microscope that moves using pseudopodia and engulfs food. Identify the kingdom and justify your classification with two features. Also, explain why this organism cannot be placed under Plantae.
Answer:
Case Deconstruction

The organism belongs to Kingdom Protista due to its unicellular nature and use of pseudopodia for movement and feeding.

Theoretical Application
  • Features: Eukaryotic cell structure, heterotrophic nutrition.
  • Example: Amoeba exhibits similar characteristics.
Critical Evaluation

It cannot be classified under Plantae due to the absence of cell walls and chlorophyll, which are essential for photosynthesis.

Question 10:
A lichen is discovered in a polluted urban area, showing a symbiotic relationship between algae and fungi. Explain the ecological role of lichens and how this relationship benefits both organisms. Provide an example of another symbiotic association in nature.
Answer:
Case Deconstruction

Lichens act as bioindicators of air quality due to their sensitivity to pollutants.

Theoretical Application
  • Algae provide photosynthates, while fungi offer shelter and minerals.
  • Example: Mycorrhiza (fungus-plant root symbiosis).
Critical Evaluation

This mutualism ensures survival in harsh environments, as seen in Xanthoria parietina, a pollution-tolerant lichen.

Question 11:
A marine biologist discovers a dinoflagellate causing red tides. Describe its classification and two harmful effects of algal blooms. Compare its mode of nutrition with cyanobacteria.
Answer:
Case Deconstruction

Dinoflagellates are Protists under Pyrrophyta, known for bioluminescence and toxins.

Theoretical Application
  • Harmful effects: Oxygen depletion, shellfish poisoning.
  • Example: Gonyaulax causes paralytic shellfish poisoning.
Critical Evaluation

Unlike cyanobacteria (autotrophic), dinoflagellates exhibit mixotrophy, combining photosynthesis and predation.

Question 12:
A farmer observes nitrogen-fixing nodules on legume roots. Identify the bacterium involved and explain its role in the nitrogen cycle. How does this differ from free-living nitrogen fixers like Azotobacter?
Answer:
Case Deconstruction

The bacterium is Rhizobium, which forms mutualistic nodules for nitrogen fixation.

Theoretical Application
  • Role: Converts atmospheric N2 to ammonia (nitrogenase enzyme).
  • Example: Clover plants host Rhizobium.
Critical Evaluation

Azotobacter fixes nitrogen independently, lacking host-specific symbiosis seen in Rhizobium.

Question 13:
A student observed a microorganism under the microscope that lacked a well-defined nucleus and had a cell wall made of peptidoglycan. The organism could survive in extreme environments like hot springs.

(a) Identify the kingdom to which this organism belongs.

(b) Give two characteristics of this kingdom.

(c) Why can this organism survive in extreme conditions?

Answer:

(a) The organism belongs to the kingdom Monera, specifically Archaebacteria.


(b) Two characteristics of this kingdom are:

  • They are prokaryotic, lacking a well-defined nucleus and membrane-bound organelles.
  • Their cell wall composition varies; in this case, it is made of peptidoglycan.


(c) This organism can survive in extreme conditions due to its unique cell membrane structure, which contains branched lipids that provide stability under high temperatures or acidic conditions. Additionally, their enzymes and metabolic pathways are adapted to function optimally in harsh environments.

Question 14:
A farmer noticed white cottony growth on decaying organic matter in his field. Upon microscopic examination, the structures showed thread-like hyphae and spore-bearing bodies.

(a) Identify the kingdom and the specific group of organisms observed.

(b) Explain how these organisms obtain nutrition.

(c) How do they contribute to the ecosystem?

Answer:

(a) The organism belongs to the kingdom Fungi, specifically the group Zygomycetes or Deuteromycetes, as indicated by the presence of hyphae and spore-bearing bodies.


(b) These organisms obtain nutrition through saprophytic mode, meaning they secrete digestive enzymes onto the decaying organic matter and absorb the digested nutrients.


(c) They play a crucial role in the ecosystem as decomposers, breaking down dead organic material and recycling nutrients back into the soil. This process enriches the soil and supports plant growth, maintaining ecological balance.

Question 15:
A student observed a microorganism under the microscope that lacked a well-defined nucleus and membrane-bound organelles. It was found in extreme environments like hot springs. Identify the kingdom of this organism and explain two characteristic features of this kingdom.
Answer:

The organism belongs to the kingdom Monera.

Two characteristic features of this kingdom are:

  • Prokaryotic cells: Organisms in this kingdom lack a well-defined nucleus and membrane-bound organelles. Their genetic material is dispersed in the cytoplasm.
  • Extreme environment adaptability: Many members, like archaebacteria, thrive in extreme conditions such as hot springs, salty areas, or marshy regions due to their unique cell wall composition and metabolic pathways.

Additionally, they reproduce asexually, mainly through binary fission, and play vital roles in nitrogen fixation and decomposition.

Question 16:
A farmer noticed white cottony growth on decaying organic matter in his field. Upon microscopic examination, the growth showed thread-like structures with spores. Identify the kingdom and division of this organism. Describe its mode of nutrition and ecological importance.
Answer:

The organism belongs to the kingdom Fungi and division Deuteromycota (if asexual spores are observed) or Ascomycota/Basidiomycota (if sexual spores are present).

Mode of nutrition: Fungi exhibit saprophytic nutrition, absorbing nutrients from decaying organic matter by secreting digestive enzymes externally.

Ecological importance:

  • Decomposers: They break down complex organic matter, recycling nutrients back into the soil.
  • Symbiotic relationships: Some fungi form mutualistic associations with plant roots (mycorrhizae), enhancing nutrient absorption.

Fungi also have industrial applications, such as in antibiotic production (e.g., Penicillium) and food fermentation (e.g., yeast).

Question 17:
A student observed a microorganism under a microscope and noted the following features: unicellular, cell wall made of peptidoglycan, and absence of a well-defined nucleus. Identify the kingdom this organism belongs to and justify your answer with two additional characteristics of this kingdom.
Answer:

The organism belongs to the kingdom Monera because it exhibits key features such as being unicellular, having a cell wall made of peptidoglycan, and lacking a well-defined nucleus (prokaryotic nature).

Two additional characteristics of the kingdom Monera are:

  • They can be autotrophic (like cyanobacteria) or heterotrophic (like most bacteria).
  • They reproduce mainly through binary fission, a simple asexual method.

This kingdom includes bacteria and cyanobacteria, which are crucial for processes like nitrogen fixation and decomposition in ecosystems.

Question 18:
A group of students collected a slimy, green organism from a pond. Under the microscope, it appeared as a filamentous structure with no distinct organs. The organism could perform photosynthesis. Identify the kingdom and division of this organism, and explain two reasons why it cannot be classified under Plantae.
Answer:

The organism belongs to the kingdom Protista and the division Chlorophyta (green algae) because it is filamentous, photosynthetic, and lacks distinct organs.

Two reasons why it cannot be classified under Plantae are:

  • It lacks true roots, stems, or leaves, which are characteristic of plants.
  • It does not have embryo formation or multicellular reproductive structures like plants.

Despite being photosynthetic, algae like this are placed in Protista due to their simpler cellular organization and reproductive methods compared to plants.

Question 19:
A student observed a microorganism under a microscope that appeared to have a whip-like structure for movement. The organism was unicellular and lacked a well-defined nucleus. Based on these observations, answer the following:

(i) Identify the kingdom to which this organism belongs.
(ii) Give two characteristics of this kingdom.
(iii) Why is this organism considered more primitive than organisms in the kingdom Protista?
Answer:

(i) The organism belongs to the kingdom Monera.

(ii) Two characteristics of this kingdom are:

  • They are prokaryotic, meaning they lack a well-defined nucleus and membrane-bound organelles.
  • They may possess flagella or other simple structures for movement.

(iii) This organism is considered more primitive than those in the kingdom Protista because:
Monerans lack a true nucleus and other complex organelles, whereas Protists are eukaryotic with well-defined nuclei.
Monerans have simpler cellular organization and lack the diversity in modes of nutrition (like photosynthesis or ingestion) seen in Protists.

Question 20:
A group of students collected a sample of water from a pond and observed it under a microscope. They noticed organisms that were multicellular, filamentous, and had cell walls made of chitin. Some of these organisms were reproducing by forming spores.

(i) Identify the kingdom to which these organisms belong.
(ii) Why are they not classified under the plant kingdom?
(iii) Explain the role of chitin in their cell walls.
Answer:

(i) These organisms belong to the kingdom Fungi.

(ii) They are not classified under the plant kingdom because:

  • Fungi lack chlorophyll and cannot perform photosynthesis, unlike plants.
  • Their cell walls are made of chitin, whereas plant cell walls are made of cellulose.

(iii) Chitin in their cell walls provides:
Structural strength and rigidity, allowing fungi to maintain their shape.
Protection against environmental stresses, such as osmotic pressure.
Chitin is also a nitrogen-containing polysaccharide, which makes it more resistant to degradation compared to cellulose.

Question 21:
A student observed a microorganism under a microscope that appeared to have a cell wall but lacked a well-defined nucleus. Further analysis showed the presence of peptidoglycan in its cell wall.

(a) Identify the kingdom to which this organism belongs.
(b) Give two distinguishing features of this kingdom.

Answer:

(a) The organism belongs to the kingdom Monera because it lacks a well-defined nucleus (prokaryotic) and has a cell wall made of peptidoglycan.

(b) Two distinguishing features of kingdom Monera are:

  • They are prokaryotic, meaning they lack a membrane-bound nucleus and other organelles.
  • Their cell wall is composed of peptidoglycan, a unique feature not found in other kingdoms.

Additionally, organisms in this kingdom can be autotrophic or heterotrophic and are found in diverse habitats, including extreme environments.

Question 22:
A group of students collected a slimy, green organism from a stagnant pond. Under the microscope, it showed chlorophyll-containing structures but lacked true roots, stems, or leaves.

(a) Identify the kingdom and probable division of this organism.
(b) Explain why this organism is not classified under Plantae despite having chlorophyll.

Answer:

(a) The organism belongs to the kingdom Protista and is likely from the division Chlorophyta (green algae) due to its chlorophyll content and aquatic habitat.

(b) Although it contains chlorophyll, it is not classified under Plantae because:

  • It lacks true roots, stems, or leaves, which are defining features of plants.
  • It is unicellular or simple multicellular, whereas plants are complex multicellular organisms with specialized tissues.

Protists are a diverse group that includes algae, which share some characteristics with plants but do not exhibit the complexity of plant structures.

Chat on WhatsApp