Class 11 Biology - CBSE
Biological Classification
The Chapter Biological Classification in Class 11 CBSE Biology introduces the scientific method of grouping organisms based on shared characteristics. It covers Aristotle's early classification, and progresses through the Two-Kingdom, Three-Kingdom, Four-Kingdom, and ultimately the widely accepted Five-Kingdom Classification proposed by R.H. Whittaker in 1969. You will study the detailed structures, modes of nutrition, and reproduction of Kingdoms Monera, Protista, Fungi, Plantae, and Animalia. Additionally, the chapter explores non-cellular entities like viruses, viroids, prions, and lichens. This chapter is exceptionally high-yielding for CBSE board exams and NEET, frequently featuring comparative questions and diagrams.
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Five-Kingdom Classification
Proposed by R.H. Whittaker, it classifies organisms into Monera, Protista, Fungi, Plantae, and Animalia based on cell structure, thallus organization, mode of nutrition, reproduction, and phylogenetic relationships.
Kingdom Monera
Comprises solely of prokaryotic bacteria, which are categorized into Archaebacteria (extremophiles) and Eubacteria (true bacteria), notable for their lack of a true nucleus and membrane-bound organelles.
Kingdom Protista
Includes single-celled eukaryotes such as Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds, and Protozoans, representing a diverse group that acts as a bridge to multicellular kingdoms.
Kingdom Fungi
Heterotrophic, spore-forming eukaryotic organisms with cell walls made of chitin, categorized into Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes based on spore formation and mycelium structure.
Viruses, Viroids, and Lichens
Acellular infectious agents (viruses and viroids) containing genetic material wrapped in a protein coat, alongside symbiotic associations of algae and fungi known as lichens.
Important Formulas
Board Exam Info
In CBSE Class 11 Biology examinations, this chapter typically carries around 4 to 6 marks. Common question types include direct differentiation questions (e.g., Archaebacteria vs Eubacteria, Ascomycetes vs Basidiomycetes), short-answer questions explaining viral structure or the economic importance of fungi, and diagram-based questions identifying bacteriophages or tobacco mosaic virus (TMV).
Frequently Asked Questions
Why are viruses not included in Whittaker's Five-Kingdom classification?
Viruses are non-cellular organisms that are inert outside a host cell and do not possess true cellular machinery, which violates the basic criteria of the five-kingdom system.
What is the difference between a viroid and a virus?
A virus consists of genetic material enclosed in a protein coat, whereas a viroid is a free infectious RNA molecule without any protein coat.
How do fungi differ from plants if both have cell walls?
Plant cell walls are made of cellulose and plants are autotrophic (photosynthetic), whereas fungal cell walls are made of chitin and fungi are heterotrophic (saprophytic or parasitic).
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