Biological Classification (Class 11 Botany)

Lecture Overview

• Instructor: Ayushi Agarwal
• Subject: Biological Classification (Class 11 Botany, Chapter 2)

Overview

• Continuation of the first chapter 'Living World'
• Focus on taxonomy, classification, and identification
• Study of the groups organisms are divided into after classification

Importance of Biological Classification

• Essential for understanding biodiversity (17-18 lakh species discovered)
• Helps exploit benefits of organisms (e.g., food, shelter, clothing)
• Enables understanding and utilization of biodiversity

Historical Context

Aristotle's Classification

• Divided organisms into plants and animals
• Plants further divided based on size into herbs, shrubs, trees
• Animals divided based on presence of RBCs into Enama (with RBCs) and Anima (without RBCs)
• Simple, initial classification

Linnaeus's Two Kingdom System

• Formal system using the term kingdom
• Two Kingdoms: Plantae and Animalia
• Features used:
  • Cell wall (present- Plantae, absent- Animalia)
  • Nutritional mode: autotrophs (plants) vs heterotrophs (animals)
  • Motility
  • Response to stimuli (slow in plants, quick in animals)
  • Contractile vacuole (present- Animalia, absent- Plantae)

Subsequent Classification Systems

Ernst Haeckel's Three Kingdoms

• Introduced Protista for unicellular eukaryotes
• Classifications: Animalia, Plantae, Protista

Copeland's Four Kingdoms

• Added Monera for prokaryotic organisms (bacteria)
• Classifications: Animalia, Plantae, Protista, Monera

R.H. Whittaker's Five Kingdoms

• Added Fungi as a separate kingdom
• Classifications: Animalia, Plantae, Protista, Monera, Fungi
• Key basis: Mode of nutrition
  • Animalia: heterotrophic
  • Plantae: autotrophic
  • Fungi: heterotrophic, saprophytic
  • Protista: varied (auto-, hetero-, mixotrophic)
  • Monera: diverse (autotrophic, heterotrophic)

Carl Woese's Six Kingdoms & Three Domains System

• Divided Monera into Archaebacteria and Eubacteria
• Introduced domain above kingdom:
  • Domains: Archaea, Bacteria, Eukarya
  • Kingdoms: Archaebacteria, Eubacteria, Protista, Plantae, Fungi, Animalia
• Key basis: Gene sequencing of 16s rRNA

Kingdom Monera

• Sole members: Bacteria
• Characteristics: Prokaryotic cells, genetic material (naked DNA), no membrane-bound organelles
• Diversity in morphology (shape), nutrition, respiration, and reproduction
• Types of Bacteria Shapes:
  • Bacillus: Rod-shaped
  • Coccus: Spherical
  • Spirillum: Spiral
  • Vibrio: Comma-shaped
• Respiration: Obligate aerobes, obligate anaerobes, facultative aerobes, facultative anaerobes

Kingdom Protista

• Eukaryotic, mostly unicellular
• Divided into producers (photosynthetic), consumers (saprophytic), protozoans (animal-like)
• Key organisms/types summarized:
  • Photosynthetic Protista: Diatoms, Dinoflagellates, Euglenoids
  • Consumer Protista: Slime molds
  • Protozoans: Amoeboid, Ciliated, Flagellated, Sporozoans

Kingdom Fungi

• Multicellular eukaryotic heterotrophs
• Cell wall: Chitin (mostly)
• Body structure: Mycelium (network of hyphae)
• Reproduction: Asexual (spores), sexual
• Classification: Phycomycetes, Ascomycetes, Basidiomycetes, Deuteromycetes

Viruses and Subviral Agents

• Viruses: Acellular, considered as connecting link between living and non-living
  • Structure: Capsid (protein), genetic material (DNA or RNA), envelope (optional)
  • Examples: TMV, Bacteriophage
• Viroids: Infectious RNA particles
• Virusoids: Require a helper virus
• Prions: Infectious proteins

Lichens and Mycorrhizae

• Lichens: Mutualistic association between algae and fungi
• Mycorrhizae: Mutualistic association between fungi and roots of higher plants

Conclusion

• Chapter covered multiple key areas of classification and different kingdoms
• Important for understanding biological diversity and evolution of classification systems

Questions and Revision

• Discussed previous NEET exam questions related to topics
• Emphasized importance of revising NCRT and understanding concepts clearly