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Biology · Class 11 Science

Ch 2Biological Classification — Class 11 Biology, concept-first.

For a very long time, biologists tried to fit every living organism into just two large groups: Plantae (plants) and Animalia (animals). This two-kingdom system, associated with Carl Linnaeus, used a simple set of visible traits to sort organisms -- plants were distinguished by having a cell wall, being generally stati…

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Key concepts

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Five Kingdom Classification

Whittaker's system classifying organisms into Monera, Protista, Fungi, Plantae and Animalia based on cell structure, body organisation, mode of nutrition and phylogenetic relationships.

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Chapter contents

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2.1

From Two Kingdoms to Five: Why Classification Systems Changed

For a very long time, biologists tried to fit every living organism into just two large groups: Plantae (plants) and Animalia (animals).

2.2

Whittaker's Five Kingdom Classification and Its Basis

In 1969, the American ecologist R.H. Whittaker proposed a five-kingdom classification that remains the most widely taught scheme in Indian school biology.

2.3

Kingdom Monera

Kingdom Monera contains every prokaryotic organism -- that is, every organism whose cell lacks a true, membrane-bound nucleus and membrane-bound cell organelles.

2.4

Kingdom Protista

Kingdom Protista is often described as a 'link' or 'bridge' kingdom, because it includes single-celled eukaryotic organisms that show characteristics transitional between the simplest prokaryotes and…

2.5

Kingdom Fungi

Kingdom Fungi comprises eukaryotic, heterotrophic, and (with the notable exception of unicellular yeasts) mostly multicellular organisms.

2.6

Lichens

A lichen is not a single organism at all, but a remarkably close and stable symbiotic association between two very different partners: an alga and a fungus.

2.7

Viruses, Viroids and Prions

Beyond the five kingdoms lies a fascinating group of agents that stretch the very definition of what it means to be 'living' -- viruses, viroids and prions.

Summary

This chapter traced how classification systems evolved from Linnaeus's simple two-kingdom scheme, through the recognition of bacteria, fungi and single-celled organisms that did not neatly fit as eith…

Very Short Answer Questions

+Show 6 questions6 questions
  1. Q11Define the term 'phylogeny' as used in the context of biological classification.Free
  2. Q12Name the smallest living cells known, which are completely devoid of a cell wall and can survive without oxygen.Free
  3. Q13Name the blue-green pigment found in cyanobacteria, and name the specialised structure some filamentous cyanobacteria use to fix atmospheric…Preview
  4. Q14Give one example each of a fungus belonging to class Ascomycetes and a fungus belonging to class Basidiomycetes.Preview
  5. Q15Name the virus that causes Tobacco Mosaic Disease, and state the type of nucleic acid its genome is made of.Preview
  6. Q16Who discovered viroids, and in which year were they discovered?Preview

Short Answer Questions

+Show 10 questions10 questions
  1. Q17Discuss briefly why the two-kingdom classification system proposed by Linnaeus (Plantae and Animalia) proved inadequate as a scheme for clas…Free
  2. Q18List the five broad criteria (basis) that R.H. Whittaker used to place organisms into his five-kingdom system of classification.Free
  3. Q19Differentiate between Archaebacteria and Eubacteria with respect to their cell-wall chemistry and the habitats in which they are typically f…Free
  4. Q20Give an account of the nutritional and habitat diversity found within Kingdom Monera, referring to autotrophic, heterotrophic and chemosynth…Preview
  5. Q21Describe the salient features shared by members of Kingdom Protista as a whole, in terms of their cell structure and mode of reproduction.Preview
  6. Q22Give a comparative account of chrysophytes, dinoflagellates and euglenoids under Kingdom Protista, highlighting one distinguishing feature o…Preview
  7. Q23Describe the life-cycle feature that makes slime moulds distinctive among the Protista, and briefly state how protozoans are grouped on the…Preview
  8. Q24Describe the salient features of class Phycomycetes and class Ascomycetes under Kingdom Fungi, giving one example of each.Preview
  9. Q25Describe the salient features of class Basidiomycetes and class Deuteromycetes under Kingdom Fungi, giving one example of each.Preview
  10. Q26What is a lichen? Explain the respective roles of the phycobiont and the mycobiont in this symbiotic association.Preview

Long Answer Questions

+Show 6 questions6 questions
  1. Q27Trace the historical development of biological classification from the two-kingdom system through to Whittaker's five-kingdom system, explai…Free
  2. Q28Explain in detail the five criteria (cell structure, body organisation, mode of nutrition, mode of reproduction, and phylogenetic relationsh…Free
  3. Q29Give a detailed account of Kingdom Monera, covering its two broad sub-groups Archaebacteria and Eubacteria (including cyanobacteria and myco…Preview
  4. Q30Describe in detail the major groups of Kingdom Protista (chrysophytes, dinoflagellates, euglenoids, slime moulds and protozoans), giving the…Preview
  5. Q31Give a detailed comparative account of the four classes of Kingdom Fungi (Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes) with…Preview
  6. Q32Describe the structure, genetic material and mode of replication of viruses with reference to the tobacco mosaic virus and a bacteriophage,…Preview

More questions

+Show 10 questions10 questions
  1. Q1Which of the following criteria was NOT used by Whittaker in proposing his five-kingdom system of classification? (a) Cell structure (b) Bod…Free
  2. Q2Archaebacteria are placed in a group separate from other bacteria mainly because of a difference in the: (a) Shape of the cell (b) Chemistry…Free
  3. Q3Cyanobacteria are also commonly known as: (a) Green algae (b) Blue-green algae (c) Golden algae (d) Brown algaeFree
  4. Q4Which of the following is correctly described as an organism that completely lacks a cell wall and is the smallest living cell known? (a) My…Preview
  5. Q5Diatoms are placed under which group of Kingdom Protista? (a) Dinoflagellates (b) Chrysophytes (c) Euglenoids (d) Slime mouldsPreview
  6. Q6Dinoflagellates that appear red and are responsible for colouring the sea red (giving the Red Sea its name) belong to the genus: (a) Gonyaul…Preview
  7. Q7Under unfavourable conditions, plasmodial slime moulds form structures that help them tide over adverse conditions. These structures are cal…Preview
  8. Q8A saprophytic fungus commonly seen growing on moist bread, belonging to class Phycomycetes, is: (a) Rhizopus (b) Agaricus (c) Saccharomyces…Preview
  9. Q9A lichen represents a symbiotic association between: (a) A bacterium and a virus (b) An alga and a fungus (c) A fungus and a moss (d) A prot…Preview
  10. Q10Viroids, discovered in 1971 as the causative agents of potato spindle tuber disease, were first described by: (a) D.J. Ivanowsky (b) M.W. Be…Preview