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Diversity of the Living World – CBSE NCERT Study Resources

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11th

11th - Biology

Diversity of the Living World

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Overview of the Chapter

This chapter introduces students to the vast diversity of life forms on Earth. It covers the fundamental concepts of biodiversity, classification, and the need for systematic study of living organisms. The chapter also explains the taxonomic hierarchy and the importance of binomial nomenclature in biology.

Biodiversity: The variety of life forms found in a particular region or on the entire planet, including diversity within species, between species, and of ecosystems.

What is Living?

The chapter begins by defining the characteristics of living organisms, such as growth, reproduction, metabolism, response to stimuli, and adaptation. It distinguishes between living and non-living entities.

Metabolism: The sum total of all chemical reactions occurring in an organism to maintain life.

Taxonomic Categories

The chapter explains the hierarchical system of classification, which includes:

  • Kingdom
  • Phylum (for animals) or Division (for plants)
  • Class
  • Order
  • Family
  • Genus
  • Species

Species: A group of organisms capable of interbreeding and producing fertile offspring.

Binomial Nomenclature

The chapter discusses the system of naming organisms using two names (genus and species) as proposed by Carolus Linnaeus. For example, humans are named Homo sapiens.

Five Kingdom Classification

The chapter details R.H. Whittaker's five-kingdom classification system:

  1. Monera (prokaryotes)
  2. Protista (unicellular eukaryotes)
  3. Fungi (heterotrophic eukaryotes)
  4. Plantae (multicellular autotrophs)
  5. Animalia (multicellular heterotrophs)

Prokaryotes: Organisms lacking a well-defined nucleus and membrane-bound organelles.

Viruses, Viroids, and Lichens

The chapter concludes with a discussion of acellular organisms like viruses and viroids, as well as symbiotic associations like lichens, which are indicators of pollution.

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 taxonomy.
Answer:
Taxonomy is the science of classification of organisms.
Question 2:
Name the five-kingdom classification proposed by Whittaker.
Answer:
  • Monera
  • Protista
  • Fungi
  • Plantae
  • Animalia
Question 3:
What is binomial nomenclature?
Answer:

It is a naming system with Genus and species.

Question 4:
Give two examples of prokaryotic organisms.
Answer:
  • Bacteria
  • Blue-green algae
Question 5:
What is the basis of biological classification?
Answer:

It is based on morphology and evolutionary relationships.

Question 6:
Name the taxonomic hierarchy categories in order.
Answer:
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
Question 7:
What are lichens?
Answer:

Symbiotic association of algae and fungi.

Question 8:
Give two examples of saprophytic fungi.
Answer:
  • Mushroom
  • Rhizopus
Question 9:
Define viroids.
Answer:

Infectious agents with only RNA, no protein coat.

Question 10:
Name two protozoan diseases.
Answer:
  • Malaria
  • Amoebic dysentery
Question 11:
What are archaebacteria?
Answer:

Ancient bacteria thriving in extreme environments.

Question 12:
Give two examples of ascomycetes.
Answer:
  • Yeast
  • Penicillium
Question 13:
What is the significance of diatoms?
Answer:

They form diatomaceous earth used in filtration.

Question 14:
What is the binomial nomenclature system?
Answer:

The binomial nomenclature system assigns a two-part scientific name to organisms: Genus (capitalized) and species (lowercase), e.g., Homo sapiens.

Question 15:
Name the five kingdoms proposed by R.H. Whittaker.
Answer:

The five kingdoms are:

  • Monera
  • Protista
  • Fungi
  • Plantae
  • Animalia

Question 16:
What is the role of lichens in ecological succession?
Answer:

Lichens are pioneer species that colonize barren rocks and release acids to break them down, forming soil for other organisms.

Question 17:
Differentiate between eukaryotic and prokaryotic cells.
Answer:

  • Prokaryotic cells lack a nucleus and membrane-bound organelles.
  • Eukaryotic cells have a well-defined nucleus and organelles.

Question 18:
What are viroids?
Answer:

Viroids are infectious agents smaller than viruses, consisting only of single-stranded RNA without a protein coat.

Question 19:
Why are cyanobacteria called blue-green algae?
Answer:

Cyanobacteria contain chlorophyll-a and phycocyanin pigments, giving them a blue-green color, hence the name.

Question 20:
What is the significance of diatoms in ecosystems?
Answer:

Diatoms are primary producers in aquatic ecosystems and their silica-rich cell walls form diatomaceous earth, used in filters.

Question 21:
How do archaebacteria survive in extreme conditions?
Answer:

Archaebacteria have unique cell membrane lipids and enzymes that stabilize them in extremes like high salt, heat, or acidity.

Question 22:
What is the basis of classification in fungi?
Answer:

Fungi are classified based on reproductive structures (e.g., spores) and mycelium type (septate or coenocytic).

Question 23:
Why are viruses considered non-living?
Answer:

Viruses lack cellular structure and cannot perform metabolic activities outside a host cell, making them non-living.

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:
Define taxonomy and state its importance.
Answer:

Taxonomy is the science of identifying, naming, and classifying organisms based on shared characteristics.
Its importance includes:

  • Organizing biodiversity for systematic study
  • Providing a universal naming system (Binomial Nomenclature)
  • Helping in conservation efforts by identifying species

Question 2:
What are the five kingdoms proposed by Whittaker?
Answer:

Whittaker's five kingdoms are:

  • Monera (prokaryotes)
  • Protista (unicellular eukaryotes)
  • Fungi (saprophytic eukaryotes)
  • Plantae (multicellular autotrophs)
  • Animalia (multicellular heterotrophs)

Question 3:
Differentiate between phylogeny and systematics.
Answer:

Phylogeny studies evolutionary relationships among organisms, while systematics includes both classification and evolutionary history.
Key difference: Phylogeny focuses on ancestry, systematics on both grouping and ancestry.

Question 4:
Why are viruses not included in Whittaker's classification?
Answer:

Viruses lack cellular structure and cannot reproduce independently (require host).
They don't fit into any kingdom as they exhibit both living (replication) and non-living (crystallization) characteristics.

Question 5:
What is the basis of three-domain system of classification?
Answer:

The three-domain system (by Woese) is based on rRNA sequences and divides life into:

  • Archaea (extremophiles)
  • Bacteria (true bacteria)
  • Eukarya (all eukaryotes)

Question 6:
Name the taxonomic aids used for preserving plant and animal specimens.
Answer:

Common taxonomic aids include:

  • Herbarium (dried plant specimens)
  • Museum (preserved animals/skeletons)
  • Botanical gardens (live plants)
  • Zoological parks (live animals)

Question 7:
Explain the term binomial nomenclature with an example.
Answer:

Binomial nomenclature assigns a two-part scientific name: Genus (capitalized) + species (lowercase).
Example: Homo sapiens for humans.
It ensures universal understanding and avoids regional naming conflicts.

Question 8:
What are lichens? State their ecological significance.
Answer:

Lichens are symbiotic associations between fungi and algae/cyanobacteria.
Ecological roles:

  • Pioneer species in succession
  • Air pollution indicators
  • Soil formation through weathering

Question 9:
List two features that distinguish algae from fungi.
Answer:

Differences:

  • Nutrition: Algae are autotrophic (photosynthetic), fungi are heterotrophic (saprophytic/parasitic)
  • Cell wall: Algae have cellulose, fungi have chitin

Question 10:
Why are cyanobacteria called blue-green algae?
Answer:

Cyanobacteria are called blue-green algae due to their blue-green pigments (phycocyanin) and algae-like photosynthesis.
However, they're prokaryotes (lack membrane-bound organelles), unlike true algae.

Question 11:
What is the role of ICBN and ICZN in nomenclature?
Answer:

ICBN (International Code of Botanical Nomenclature) and ICZN (International Code of Zoological Nomenclature) provide rules for naming plants and animals respectively.
They ensure standardized, unique scientific names globally.

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 monera and protista based on cellular organization and mode of nutrition.
Answer:

Monera are prokaryotic organisms with a simple cellular structure lacking a nucleus and membrane-bound organelles. They exhibit diverse modes of nutrition, including autotrophic (e.g., cyanobacteria) and heterotrophic (e.g., bacteria).

Protista are eukaryotic organisms with a well-defined nucleus and organelles. Their nutrition can be autotrophic (e.g., algae), heterotrophic (e.g., protozoa), or mixotrophic (e.g., Euglena).

Key difference: Monera lack membrane-bound organelles, while Protista possess them.

Question 2:
Explain the significance of binomial nomenclature in biological classification.
Answer:

Binomial nomenclature is a universal system of naming organisms using two terms: genus (capitalized) and species (lowercase). For example, Homo sapiens for humans.

Significance:

  • Provides a standardized naming system globally.
  • Avoids confusion caused by common names.
  • Reflects evolutionary relationships.

It ensures clarity and precision in scientific communication.

Question 3:
Describe the key features of fungi distinguishing them from plants.
Answer:

Fungi differ from plants in several ways:

  • Cell wall composition: Fungi have chitin, while plants have cellulose.
  • Nutrition: Fungi are heterotrophic (absorb nutrients), whereas plants are autotrophic (photosynthesis).
  • Reproduction: Fungi reproduce via spores, while plants use seeds or spores.

Fungi lack chlorophyll, unlike plants, which are photosynthetic.

Question 4:
What are lichens? Explain their ecological importance.
Answer:

Lichens are symbiotic associations between fungi (mycobiont) and algae or cyanobacteria (photobiont).

Ecological importance:

  • Pioneer species: Colonize barren rocks and initiate soil formation.
  • Bioindicators: Sensitive to air pollution, especially sulfur dioxide.
  • Nutrient cycling: Contribute to nitrogen fixation in ecosystems.

They play a vital role in harsh environments.

Question 5:
How do viruses differ from living organisms? Provide two examples.
Answer:

Viruses differ from living organisms because:

  • They lack cellular structure and metabolic machinery.
  • They cannot reproduce independently; require a host cell.

Examples:
1. HIV (Human Immunodeficiency Virus)
2. Tobacco Mosaic Virus (TMV)

Viruses are considered obligate intracellular parasites.

Question 6:
Compare the five-kingdom and three-domain systems of classification.
Answer:

Five-kingdom system (Whittaker) classifies life into Monera, Protista, Fungi, Plantae, and Animalia based on cell structure and nutrition.

Three-domain system (Woese) divides life into Bacteria, Archaea, and Eukarya based on molecular differences (e.g., rRNA).

Key difference: The three-domain system separates Archaea from Bacteria due to distinct genetic and biochemical traits, providing a more accurate evolutionary perspective.

Question 7:
How does the five-kingdom classification system improve upon the earlier two-kingdom system?
Answer:

The five-kingdom system (Monera, Protista, Fungi, Plantae, Animalia) resolves limitations of the two-kingdom system (Plantae and Animalia) by:

  • Separating prokaryotes (Monera) from eukaryotes.
  • Grouping unicellular eukaryotes under Protista.
  • Recognizing Fungi as a distinct kingdom due to chitinous cell walls and heterotrophy.

This reflects evolutionary relationships and diversity more accurately.

Question 8:
List three unique characteristics of archaebacteria and their habitats.
Answer:

Archaebacteria thrive in extreme environments due to:

  • Cell membrane lipids: Branched chains for stability in harsh conditions.
  • Cell wall: Lacks peptidoglycan, unlike eubacteria.
  • Genetic machinery: Resembles eukaryotes in transcription/translation.

Habitats include:

  • Thermophiles: Hot springs (e.g., Thermococcus).
  • Halophiles: Salty lakes (e.g., Halobacterium).
  • Methanogens: Anaerobic swamps (e.g., Methanobacillus).

Question 9:
Why are viruses considered non-living? Provide two reasons.
Answer:

Viruses are non-living because:

  • They lack cellular structure and metabolic machinery (no respiration, growth).
  • They cannot reproduce independently; require a host cell for replication.

However, they exhibit living traits like mutation and host-specificity only inside host cells.

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 system proposed by R.H. Whittaker. Highlight its advantages over the two-kingdom system.
Answer:
Theoretical Framework

R.H. Whittaker's five-kingdom classification divides organisms into Monera, Protista, Fungi, Plantae, and Animalia based on cell structure, nutrition, and reproduction. Our textbook shows this system resolved limitations of the two-kingdom system, which only classified life into Plantae and Animalia.

Evidence Analysis
  • Monera includes prokaryotes (e.g., bacteria), absent in the two-kingdom system.
  • Protista accommodates unicellular eukaryotes (e.g., Amoeba), which were ambiguously placed earlier.
  • Fungi, with chitinous cell walls, were wrongly grouped with plants previously.
Critical Evaluation

This system acknowledges diversity in cellular organization and ecological roles. For example, it separates autotrophs (Plantae) from heterotrophs (Fungi). However, viruses remain unclassified.

Question 2:
Describe the economic importance of algae with two examples. How do they contribute to ecological balance?
Answer:
Theoretical Framework

Algae, as primary producers, have immense economic importance and sustain ecological balance. We studied their role in oxygen production and as food sources.

Evidence Analysis
  • Chlorella is used in protein supplements due to high nutrient content.
  • Gelidium provides agar for microbiological cultures.
  • They fix 50% of global CO₂, maintaining atmospheric balance.
Critical Evaluation

Algal blooms, however, disrupt ecosystems by depleting oxygen. Their rapid growth is both beneficial (biofuel potential) and harmful (eutrophication).

Question 3:
Compare Bryophytes and Pteridophytes based on habitat, vascular tissue, and reproduction. Provide one example of each.
Answer:
Theoretical Framework

Bryophytes (e.g., Funaria) are nonvascular plants thriving in moist habitats, while Pteridophytes (e.g., Dryopteris) possess vascular tissues and prefer drier areas.

Evidence Analysis
FeatureBryophytesPteridophytes
Vascular TissueAbsentPresent (xylem/phloem)
ReproductionDominant gametophyteDominant sporophyte
Critical Evaluation

Pteridophytes' vascular system enables taller growth, but both depend on water for fertilization, linking them to early plant evolution.

Question 4:
Analyze the adaptive features of xerophytes with two examples. How do these features ensure survival in arid conditions?
Answer:
Theoretical Framework

Xerophytes, like Opuntia and Nerium, exhibit adaptive features to minimize water loss in deserts.

Evidence Analysis
  • Thick cuticles and sunken stomata reduce transpiration.
  • Opuntia stores water in fleshy stems, while Nerium has needle-like leaves.
  • CAM photosynthesis allows stomatal opening at night.
Critical Evaluation

These adaptations trade-off growth speed for durability. For instance, Opuntia grows slowly but survives years without rain.

Question 5:
Discuss the role of lichens as bioindicators of air pollution. Why are they sensitive to sulfur dioxide?
Answer:
Theoretical Framework

Lichens, symbiotic organisms (algae + fungi), are bioindicators due to their sensitivity to pollutants like sulfur dioxide.

Evidence Analysis
  • They absorb nutrients directly from air, accumulating toxins.
  • Usnea disappears in high SO₂ areas, as the gas disrupts chlorophyll.
  • Their absence correlates with Air Quality Index (AQI) deterioration.
Critical Evaluation

While cost-effective for monitoring, lichens grow slowly, delaying real-time data. Urban areas often show "lichen deserts."

Question 6:
Explain the five-kingdom classification proposed by R.H. Whittaker. Highlight its advantages over the two-kingdom system.
Answer:
Theoretical Framework

R.H. Whittaker proposed the five-kingdom classification (Monera, Protista, Fungi, Plantae, Animalia) based on cell structure, nutrition, and phylogeny. This system resolved limitations of the two-kingdom system (Plantae and Animalia), which couldn't classify microorganisms.

Evidence Analysis
  • Monera includes prokaryotes (e.g., bacteria), while Protista covers unicellular eukaryotes (e.g., Amoeba).
  • Fungi, with chitinous cell walls, were separated from plants due to heterotrophic nutrition.
Critical Evaluation

This system improved clarity but still faced challenges like viral classification. Our textbook shows it laid groundwork for modern taxonomy.

Question 7:
Compare gymnosperms and angiosperms with respect to their reproductive structures and economic importance.
Answer:
Theoretical Framework

Gymnosperms (e.g., pine) bear naked seeds, while angiosperms (e.g., mango) enclose seeds in fruits. Both dominate terrestrial ecosystems but differ in reproduction.

Evidence Analysis
  • Gymnosperms rely on cones for pollination (wind-assisted), whereas angiosperms use flowers attracting pollinators.
  • Economically, gymnosperms provide timber (e.g., Cedrus), while angiosperms supply food (e.g., wheat).
Critical Evaluation

Angiosperms' floral diversity enhances adaptability, but gymnosperms thrive in harsher climates. Our studies highlight their complementary ecological roles.

Question 8:
Discuss the role of lichens as bioindicators and their symbiotic relationship.
Answer:
Theoretical Framework

Lichens are symbiotic associations between fungi and algae/cyanobacteria. They are sensitive to air pollution, making them ideal bioindicators.

Evidence Analysis
  • Algae provide photosynthesis-derived nutrients, while fungi offer shelter and minerals.
  • Their absence in urban areas (e.g., Delhi) indicates high SO2 levels, as per our textbook.
Critical Evaluation

Lichens’ slow growth limits real-time monitoring, but their cost-effectiveness sustains their use. Future research could enhance their diagnostic precision.

Question 9:
Analyze the key features of Arthropoda contributing to their evolutionary success.
Answer:
Theoretical Framework

Arthropoda (e.g., crabs, insects) thrive due to exoskeletons, jointed appendages, and metameric segmentation.

Evidence Analysis
  • Chitinous exoskeletons provide protection and reduce water loss, enabling desert adaptation (e.g., scorpions).
  • Specialized appendages (e.g., antennae) enhance sensory and locomotor functions.
Critical Evaluation

Despite molting risks, their diversity (1 million+ species) underscores adaptability. Our studies link this to their Cambrian explosion dominance.

Question 10:
Evaluate the ecological and economic significance of bryophytes.
Answer:
Theoretical Framework

Bryophytes (e.g., mosses) are non-vascular plants crucial for soil formation and water retention.

Evidence Analysis
  • Ecologically, they prevent erosion (e.g., Sphagnum in peatlands) and support microhabitats.
  • Economically, they’re used as packing material and in horticulture (NCERT example).
Critical Evaluation

Their sensitivity to pollution limits urban growth, but their carbon sequestration potential is understudied. Future research could expand their commercial applications.

Question 11:
Explain the Five Kingdom Classification 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 was proposed by R.H. Whittaker in 1969 to categorize living organisms based on specific criteria. This system divides life into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

Criteria used for classification:
1. Cell Structure: Prokaryotic (Monera) or Eukaryotic (others).
2. Body Organization: Unicellular (Monera, Protista) or Multicellular (Fungi, Plantae, Animalia).
3. Mode of Nutrition: Autotrophic (Plantae), Heterotrophic (Animalia, Fungi), or both (Protista).
4. Reproduction: Asexual (Monera, Protista) or Sexual (others).
5. Phylogenetic Relationships: Evolutionary history and complexity.

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: Flowering plants (e.g., Mango tree), Algae (e.g., Spirogyra).
  • Animalia: Humans, Dogs, Insects (e.g., Butterfly).

This classification system provides a broader and more scientific way to study biodiversity, considering cellular and ecological diversity.

Question 12:
Describe the distinguishing features of Archaebacteria and Eubacteria with suitable examples. How do their habitats differ?
Answer:

Archaebacteria and Eubacteria are two major groups of prokaryotes with distinct features and habitats.

Distinguishing Features:

  • Cell Wall Composition: Archaebacteria lack peptidoglycan, while Eubacteria have peptidoglycan in their cell walls.
  • Membrane Lipids: Archaebacteria have branched-chain lipids, whereas Eubacteria have straight-chain lipids.
  • RNA Polymerase: Archaebacteria have complex RNA polymerase (similar to eukaryotes), while Eubacteria have simpler RNA polymerase.

Examples:

  • Archaebacteria: Methanogens (e.g., Methanobacterium), Halophiles (e.g., Halobacterium).
  • Eubacteria: Escherichia coli, Lactobacillus.

Habitats:

  • Archaebacteria thrive in extreme environments like hot springs (Thermophiles), salty areas (Halophiles), or anaerobic conditions (Methanogens).
  • Eubacteria are found in diverse habitats, including soil, water, and inside living organisms (e.g., gut bacteria).

These differences highlight the adaptability of prokaryotes to various ecological niches.

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, proposed by R.H. Whittaker in 1969, categorizes living organisms into five kingdoms based on specific criteria. The major criteria used for this classification include:

  • Cell Structure: Prokaryotic or Eukaryotic
  • Body Organization: Unicellular or Multicellular
  • Mode of Nutrition: Autotrophic or Heterotrophic
  • Reproduction: Sexual or Asexual
  • Phylogenetic Relationship: Evolutionary history

The five kingdoms are:

  • Monera: Includes prokaryotic organisms like bacteria and cyanobacteria. Example: Escherichia coli.
  • Protista: Includes unicellular eukaryotic organisms like algae and protozoans. Example: Amoeba.
  • Fungi: Includes heterotrophic organisms with chitinous cell walls. Example: Mushrooms.
  • Plantae: Includes multicellular, autotrophic organisms with cellulose cell walls. Example: Mango tree.
  • Animalia: Includes multicellular, heterotrophic organisms without cell walls. Example: Human beings.

This system provides a broader and more scientific way to classify organisms, considering their cellular and ecological diversity.

Question 14:
Describe the key characteristics of Arthropoda, the largest phylum in the animal kingdom. Provide examples and explain how these adaptations contribute to their success.
Answer:

The phylum Arthropoda is the largest group in the animal kingdom, characterized by the following key features:

  • Segmented Body: Divided into head, thorax, and abdomen (e.g., insects) or cephalothorax and abdomen (e.g., spiders).
  • Jointed Appendages: Specialized for locomotion, feeding, and sensing (e.g., legs, antennae).
  • Exoskeleton: Made of chitin, providing protection and support.
  • Bilateral Symmetry: Body plan is symmetrical along a central axis.
  • Open Circulatory System: Blood is not confined to vessels.
  • Molting (Ecdysis): Shedding of exoskeleton to allow growth.

Examples of arthropods include:

  • Prawn (Crustacea)
  • Butterfly (Insecta)
  • Spider (Arachnida)
  • Centipede (Myriapoda)

These adaptations contribute to their success by:

  • Enabling diverse habitats (land, water, air).
  • Providing structural support and protection.
  • Allowing efficient movement and resource utilization.
  • Facilitating rapid reproduction and survival.

Arthropods dominate ecosystems due to their versatility and evolutionary advantages.

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

The Five Kingdom Classification was proposed by R.H. Whittaker in 1969 to categorize living organisms based on specific criteria. The five kingdoms are: 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).

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 comprehensive.

Question 16:
Describe the salient features of Archaebacteria and Eubacteria with suitable examples. Highlight their ecological and economic importance.
Answer:

Archaebacteria and Eubacteria are two distinct groups of prokaryotes under the kingdom Monera.

Salient features of Archaebacteria:

  • Thrive in extreme environments (e.g., hot springs, salty lakes).
  • Cell walls lack peptidoglycan.
  • Examples: Methanogens (produce methane), Halophiles (salt-loving).

Salient features of Eubacteria:

  • Found in diverse habitats (soil, water, human gut).
  • Cell walls contain peptidoglycan.
  • Examples: Escherichia coli, Lactobacillus.

Ecological Importance:

  • Archaebacteria: Methanogens help in biogas production.
  • Eubacteria: Decomposers in nutrient cycling (e.g., Rhizobium fixes nitrogen).

Economic Importance:

  • Archaebacteria: Used in bioremediation.
  • Eubacteria: Used in antibiotics (e.g., Streptomyces), curd formation (Lactobacillus).

Both groups play vital roles in maintaining ecological balance and supporting human industries.

Question 17:
Explain the Five-Kingdom Classification system proposed by R.H. Whittaker. Discuss the criteria used for this classification and give one example of each kingdom.
Answer:

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

Criteria used for classification:
1. Cell Structure: Prokaryotic or Eukaryotic.
2. Body Organization: Unicellular or Multicellular.
3. Mode of Nutrition: Autotrophic or Heterotrophic.
4. Reproduction: Asexual or Sexual.
5. Phylogenetic Relationship: Evolutionary history.

Examples of each kingdom:
1. Monera: Bacteria (e.g., Escherichia coli) - Prokaryotic, unicellular.
2. Protista: Amoeba - Eukaryotic, unicellular.
3. Fungi: Mushroom (e.g., Agaricus) - Eukaryotic, multicellular, heterotrophic.
4. Plantae: Mango tree - Eukaryotic, multicellular, autotrophic.
5. Animalia: Human - Eukaryotic, multicellular, heterotrophic.

This classification system helps in understanding the diversity of life and the evolutionary relationships between different organisms.

Question 18:
Explain the Five-Kingdom Classification proposed by R.H. Whittaker. Discuss the major 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 living organisms based on specific criteria. This system divides life into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

Major Criteria for Classification:
1. Cell Structure: Prokaryotic (Monera) vs. Eukaryotic (others).
2. Body Organization: Unicellular (Monera, Protista) or Multicellular (Fungi, Plantae, Animalia).
3. Mode of Nutrition: Autotrophic (Plantae), Heterotrophic (Animalia, Fungi), or both (Protista).
4. Reproduction: Asexual (Monera, Protista) or Sexual (others).
5. Phylogenetic Relationships: Evolutionary history and complexity.

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: Flowering plants (e.g., Mango tree), Algae (e.g., Spirogyra).
  • Animalia: Humans, Fish, Insects.

This classification system helps in understanding the diversity of life and the relationships between different organisms. It is widely accepted due to its simplicity and scientific basis.

Question 19:
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 all living organisms into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

Criteria used for classification:
1. Cell Structure: Prokaryotic or Eukaryotic.
2. Body Organization: Unicellular or Multicellular.
3. Mode of Nutrition: Autotrophic, Heterotrophic, or Saprophytic.
4. Reproduction: Asexual or Sexual.
5. Phylogenetic Relationship: Evolutionary history.

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, Ferns, Flowering plants (e.g., Mango tree).
  • Animalia: Humans, Fish, Birds.

This classification system is significant because it provides a broader and more scientific way to study biodiversity, considering cellular and ecological diversity.

Question 20:
Explain the Five-Kingdom Classification proposed by R.H. Whittaker. Discuss the major characteristics and examples of organisms belonging to each kingdom.
Answer:

The Five-Kingdom Classification system was proposed by R.H. Whittaker in 1969 to categorize living organisms based on their cellular organization, mode of nutrition, and ecological roles. This system divides life into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.


1. Monera: This kingdom includes prokaryotic organisms (lack a true nucleus and membrane-bound organelles). They are unicellular and can be autotrophic (like cyanobacteria) or heterotrophic (like bacteria). Examples: Escherichia coli, Anabaena.


2. Protista: These are eukaryotic, mostly unicellular organisms. They can be autotrophic (algae) or heterotrophic (protozoans). Examples: Amoeba, Paramecium, Euglena.


3. Fungi: Eukaryotic, multicellular (except yeast), and heterotrophic (saprophytic or parasitic). They have cell walls made of chitin. Examples: Mushrooms, Penicillium, Yeast.


4. Plantae: Eukaryotic, multicellular, autotrophic (photosynthetic) organisms with cell walls made of cellulose. Examples: Mango tree, Fern, Rose.


5. Animalia: Eukaryotic, multicellular, heterotrophic organisms without cell walls. They exhibit locomotion and sensory organs. Examples: Humans, Fish, Birds.


This classification system helps in understanding the evolutionary relationships and diversity among organisms, making it easier to study and categorize life forms.

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 observed an organism with chitinous cell walls and heterotrophic nutrition. Case Deconstruction: Identify the kingdom. Theoretical Application: Explain why it cannot be placed under Plantae. Critical Evaluation: Compare its cell wall composition with bacteria.
Answer:
Case Deconstruction: The organism belongs to Kingdom Fungi due to chitinous cell walls and heterotrophy.
Theoretical Application: Plantae have cellulose cell walls and are autotrophic, making the organism unfit for this kingdom.
Critical Evaluation: Fungi cell walls contain chitin, while bacteria have peptidoglycan. Example: Mushrooms (Fungi) vs. E. coli (Bacteria).
Question 2:
A marine biologist discovered a radially symmetrical organism with cnidoblasts. Case Deconstruction: Name the phylum. Theoretical Application: How does symmetry aid its survival? Critical Evaluation: Contrast its tissue level with Platyhelminthes.
Answer:
Case Deconstruction: The organism is from Phylum Cnidaria (e.g., jellyfish) due to radial symmetry and cnidoblasts.
Theoretical Application: Radial symmetry allows equal response to predators from all directions.
Critical Evaluation: Cnidarians have diploblastic tissues, while Platyhelminthes are triploblastic. Example: Hydra vs. Planaria.
Question 3:
A plant specimen shows parallel venation and fibrous roots. Case Deconstruction: Classify its monocot/dicot traits. Theoretical Application: Why are these traits adaptive? Critical Evaluation: Compare its seed structure with dicots.
Answer:
Case Deconstruction: It is a monocot (e.g., maize) due to parallel venation and fibrous roots.
Theoretical Application: Fibrous roots prevent soil erosion, and parallel venation maximizes light absorption.
Critical Evaluation: Monocots have single cotyledon, while dicots (e.g., bean) have two.
Question 4:
A microbe lacks membrane-bound organelles but has 70S ribosomes. Case Deconstruction: Identify its cellular organization. Theoretical Application: Explain how ribosomes aid its function. Critical Evaluation: Contrast its DNA with eukaryotes.
Answer:
Case Deconstruction: It is prokaryotic (e.g., cyanobacteria) due to absent organelles and 70S ribosomes.
Theoretical Application: 70S ribosomes enable rapid protein synthesis for survival.
Critical Evaluation: Prokaryotes have circular DNA, while eukaryotes (e.g., humans) have linear DNA.
Question 5:
An animal exhibits metameric segmentation and closed circulatory system. Case Deconstruction: Name the phylum. Theoretical Application: How does segmentation enhance mobility? Critical Evaluation: Compare its circulatory system with arthropods.
Answer:
Case Deconstruction: It belongs to Phylum Annelida (e.g., earthworm) due to segmentation and closed circulation.
Theoretical Application: Segmentation allows independent muscle movement for burrowing.
Critical Evaluation: Annelids have closed circulation, while arthropods (e.g., cockroach) have open systems.
Question 6:
A group of students observed an organism with chitinous cell walls and heterotrophic nutrition. Identify the kingdom and justify your answer with two examples.
Answer:
Case Deconstruction

The organism belongs to the kingdom Fungi due to its chitinous cell walls and heterotrophic mode of nutrition.

Theoretical Application
  • Example 1: Mucor (bread mold) exhibits similar features.
  • Example 2: Agaricus (mushroom) is another fungus with these traits.
Critical Evaluation

Our textbook shows that fungi are distinct from plants due to their cell wall composition and inability to perform photosynthesis.

Question 7:
A marine biologist discovered a multicellular organism with radial symmetry and cnidoblasts. Classify it and explain its ecological role with two examples.
Answer:
Case Deconstruction

The organism belongs to the phylum Cnidaria due to radial symmetry and presence of cnidoblasts.

Theoretical Application
  • Example 1: Aurelia (jellyfish) plays a role in marine food chains.
  • Example 2: Physalia (Portuguese man-of-war) contributes to oceanic biodiversity.
Critical Evaluation

We studied that cnidarians are crucial for maintaining coral reef ecosystems and nutrient cycling.

Question 8:
A research paper describes a prokaryotic organism thriving in hot springs with peptidoglycan cell walls. Identify its domain and discuss its adaptations with two examples.
Answer:
Case Deconstruction

The organism belongs to the domain Archaea due to its extremophilic nature and distinct cell wall composition.

Theoretical Application
  • Example 1: Thermococcus survives high temperatures through heat-stable enzymes.
  • Example 2: Sulfolobus metabolizes sulfur in acidic hot springs.
Critical Evaluation

Our textbook shows archaea have unique membrane lipids that provide thermal stability in extreme habitats.

Question 9:
A botanist found a plant with parallel venation and fibrous roots. Classify its group and compare its features with another plant group using two examples.
Answer:
Case Deconstruction

The plant belongs to monocotyledons due to parallel venation and fibrous root system.

Theoretical Application
  • Example 1: Oryza sativa (rice) shows typical monocot characteristics.
  • Example 2: Triticum aestivum (wheat) contrasts with dicots like Helianthus (sunflower).
Critical Evaluation

We studied that monocots have single cotyledon while dicots show reticulate venation and tap roots.

Question 10:
A newly discovered organism has chitinous cell walls, heterotrophic nutrition, and reproduces via spores. Analyze its classification and justify its placement in the Five Kingdom System.
Answer:
Case Deconstruction

The organism exhibits fungal traits: chitinous cell walls (like Aspergillus), absorptive nutrition, and spore reproduction.

Theoretical Application
  • Fungi Kingdom: Matches Whittaker’s criteria for cell wall composition and nutrition.
  • Excludes Plantae (autotrophic) and Animalia (no cell walls).
Critical Evaluation

Similar to Penicillium, but DNA sequencing could confirm if it’s a new phylum under Fungi.

Question 11:
A marine biologist finds a radially symmetrical, diploblastic organism with cnidocytes. Compare its features with Porifera and Ctenophora using current taxonomic data.
Answer:
Case Deconstruction

The organism belongs to Cnidaria (e.g., Aurelia) due to radial symmetry and cnidocytes.

Theoretical Application
  • Porifera: Asymmetrical, no tissues (e.g., Sycon).
  • Ctenophora: Biradial, colloblasts (e.g., Pleurobrachia).
Critical Evaluation

Recent studies place Ctenophora as a sister clade to Cnidaria, challenging traditional diploblast classification.

Question 12:
A plant specimen shows parallel venation, fibrous roots, and trimerous flowers. Deduce its class and subclass, contrasting it with dicotyledons.
Answer:
Case Deconstruction

The plant is a monocot (e.g., Oryza sativa) due to parallel venation and fibrous roots.

Theoretical Application
  • Class Liliopsida: Trimerous flowers.
  • Dicots: Reticulate venation, taproots (e.g., Helianthus).
Critical Evaluation

Genetic studies reveal monocots evolved from dicots, explaining shared traits like vascular bundles.

Question 13:
A microbe lacks a nucleus and membrane-bound organelles but has peptidoglycan cell walls. Classify it and debate its ecological role using evidence.
Answer:
Case Deconstruction

The microbe is a bacterium (e.g., E. coli) due to prokaryotic structure and peptidoglycan.

Theoretical Application
  • Kingdom Monera: Absence of nucleus.
  • Ecological role: Nitrogen fixation (e.g., Rhizobium).
Critical Evaluation

Metagenomic data shows bacterial diversity exceeds textbook estimates, impacting nutrient cycles.

Question 14:

In a biodiversity survey, a group of students observed two organisms: Paramecium and Amoeba. Both are unicellular, but they differ in their locomotion and feeding mechanisms.

(a) Compare their modes of locomotion.
(b) Explain how their feeding mechanisms differ.

Answer:

(a) Comparison of locomotion:
Paramecium moves using cilia, which are hair-like structures that beat in a coordinated manner to propel the organism.
Amoeba moves using pseudopodia (false feet), which are temporary projections of the cell membrane and cytoplasm.

(b) Difference in feeding mechanisms:
Paramecium uses cilia to sweep food particles into its oral groove, where they are engulfed into food vacuoles.
Amoeba engulfs food particles by surrounding them with pseudopodia, forming a food vacuole through phagocytosis.

Both organisms exhibit holozoic nutrition, but their methods of capturing food differ due to their structural adaptations.

Question 15:

A researcher discovered a new plant species with the following characteristics: well-differentiated body, presence of vascular tissues, and seeds enclosed in fruits.

(a) Identify the group to which this plant belongs.
(b) Give two features of this group that distinguish it from Bryophytes.

Answer:

(a) Group identification:
The plant belongs to the group Angiosperms (flowering plants), as it has seeds enclosed in fruits and well-developed vascular tissues.

(b) Distinguishing features from Bryophytes:

  • Angiosperms have vascular tissues (xylem and phloem) for conduction, whereas Bryophytes lack true vascular tissues.
  • Angiosperms produce seeds enclosed in fruits, while Bryophytes reproduce via spores and do not produce seeds or fruits.

Additionally, Angiosperms have a well-differentiated body into roots, stems, and leaves, unlike Bryophytes, which lack true roots and leaves.

Question 16:

In a biodiversity survey, a group of students observed two organisms: Paramecium and Spirogyra. They noted that Paramecium moves using cilia, while Spirogyra is a filamentous algae. Based on this, answer the following:

  • Identify the kingdom to which each organism belongs.
  • Differentiate between their modes of nutrition.
Answer:

Kingdom Identification:
Paramecium belongs to the kingdom Protista because it is a unicellular, eukaryotic organism with cilia for locomotion.
Spirogyra belongs to the kingdom Plantae (or Protista in some classifications) as it is a multicellular, photosynthetic algae.

Nutritional Differences:
Paramecium shows holozoic nutrition, ingesting food particles through a cytostome.
Spirogyra exhibits autotrophic nutrition due to the presence of chlorophyll for photosynthesis.

Additional Note: While Spirogyra is often placed under Plantae, some systems classify it under Protista due to its simple structure.

Question 17:

A researcher discovered a new species in a tropical rainforest with the following traits: chitinous cell wall, heterotrophic nutrition, and spore-producing structures.

  • Assign the correct kingdom and justify your answer.
  • Name two examples of organisms from this kingdom with economic importance.
Answer:

Kingdom Assignment:
The organism belongs to the kingdom Fungi because:

  • It has a chitinous cell wall, a defining feature of fungi.
  • It shows heterotrophic nutrition (absorptive mode).
  • The presence of spore-producing structures aligns with fungal reproduction.

Examples with Economic Importance:

  • Penicillium: Used in antibiotic (penicillin) production.
  • Saccharomyces cerevisiae: Used in bread-making and brewing due to fermentation.

Additional Note: Fungi also play a crucial role in decomposition and forming mycorrhizal associations with plants.

Question 18:
A group of students collected samples from a pond and observed various organisms under a microscope. They noted organisms with pseudopodia, cilia, and flagella. Based on their observations, answer the following:

(a) Identify the kingdom to which these organisms belong and justify your answer.
(b) Differentiate between the locomotory structures observed (pseudopodia, cilia, and flagella) with examples.
Answer:

(a) The organisms belong to the kingdom Protista. This is because Protista includes unicellular eukaryotic organisms that exhibit diverse modes of locomotion such as pseudopodia (e.g., Amoeba), cilia (e.g., Paramecium), and flagella (e.g., Euglena). These organisms are mostly aquatic and have simple cellular organization.


(b)

  • Pseudopodia: Temporary cytoplasmic extensions used for movement and feeding (e.g., Amoeba).
  • Cilia: Short, hair-like structures that beat rhythmically for movement (e.g., Paramecium).
  • Flagella: Long, whip-like structures that rotate or whip to propel the organism (e.g., Euglena).

Question 19:
A botanist discovered a plant species in a tropical rainforest with the following characteristics: vascular tissues, naked seeds, and needle-like leaves. Answer the following:

(a) Classify this plant into its division and provide two key features of this group.
(b) Explain how these adaptations (needle-like leaves) help the plant survive in its environment.
Answer:

(a) The plant belongs to the division Gymnosperms. Two key features of this group are:

  • They produce naked seeds not enclosed in fruits.
  • They have vascular tissues (xylem and phloem) for conduction.


(b) The needle-like leaves are an adaptation to reduce water loss in cold or dry environments. Their small surface area minimizes transpiration, and the thick cuticle prevents dehydration. This helps gymnosperms survive in harsh conditions like temperate forests or high altitudes.

Question 20:
A group of students collected samples from a pond and observed various organisms under a microscope. They noted the presence of Paramecium, Amoeba, and Euglena. Based on their observations, answer the following:
(a) Identify the kingdom to which these organisms belong.
(b) List two distinguishing features of this kingdom.
Answer:

(a) The organisms Paramecium, Amoeba, and Euglena belong to the kingdom Protista.

(b) Two distinguishing features of the kingdom Protista are:

  • They are mostly unicellular and eukaryotic, meaning their cells have a well-defined nucleus.
  • They exhibit diverse modes of nutrition, including autotrophic (like Euglena), heterotrophic (like Amoeba), or mixotrophic.

Additionally, protists can be free-living or parasitic, and they often reproduce both sexually and asexually.

Question 21:
During a field trip, a student observed a plant with the following characteristics:
- Well-differentiated plant body into roots, stems, and leaves
- Presence of naked seeds
- Woody stem
Identify the division to which this plant belongs and explain two key features of this division.
Answer:

The plant belongs to the division Gymnosperms.

Two key features of Gymnosperms are:

  • They produce naked seeds, meaning the seeds are not enclosed within a fruit.
  • They are mostly perennial, evergreen, and woody plants, adapted to survive in harsh conditions like cold climates.

Additionally, gymnosperms have well-developed vascular tissues (xylem and phloem) for efficient transport of water and nutrients. Examples include pine, deodar, and cycas.

Question 22:
A group of students collected samples from a pond ecosystem. They observed organisms with the following characteristics: unicellular, eukaryotic, and photosynthetic. Identify the kingdom these organisms belong to and justify your answer with two key features. Also, explain why these organisms are crucial for the pond ecosystem.
Answer:

The organisms belong to the kingdom Protista.

Justification:

  • They are unicellular and eukaryotic, which are defining features of protists.
  • Their photosynthetic nature indicates they are likely algae or phytoplankton, which are part of Protista.

These organisms are crucial for the pond ecosystem because:

  • They serve as primary producers, converting sunlight into energy through photosynthesis, forming the base of the food chain.
  • They release oxygen as a byproduct of photosynthesis, supporting aquatic life.
Question 23:
A student discovered a plant with the following traits: well-differentiated body, vascular tissues, and seeds enclosed in fruits. Classify this plant into its respective division and provide two distinguishing features. Additionally, explain how these features help the plant adapt to terrestrial environments.
Answer:

The plant belongs to the division Angiosperms (flowering plants).

Distinguishing features:

  • Presence of vascular tissues (xylem and phloem) for efficient transport of water and nutrients.
  • Seeds enclosed in fruits, which aid in seed dispersal and protection.

These features help the plant adapt to terrestrial environments because:

  • Vascular tissues allow the plant to grow taller and compete for sunlight, while also transporting water and minerals from roots to leaves.
  • Fruits attract animals for seed dispersal, ensuring wider distribution and reducing competition for resources.
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