CHAPTER 2: BIOLOGICAL CLASSIFICATION POINTS TO REMEMBER

CHAPTER 2: BIOLOGICAL CLASSIFICATION

POINTS TO REMEMBER

SYSTEMS OF CLASSIFICATION

1. Aristotle's Earliest Classification

   • Plants were classified as herbs, shrubs, and trees.
   • Animals were classified based on the presence or absence of RBCs.

2. Two-Kingdom Classification

   • Given by Carolus Linnaeus.
   • Divided into Plantae and Animalia.

3. Five-Kingdom Classification

   • Proposed by R.H. Whittaker.
   • Includes: Monera, Protista, Fungi, Plantae, and Animalia.

KINGDOM MONERA

• Includes bacteria as the sole member.
• Shapes of Bacteria:
  • Coccus: Spherical
  • Bacillus: Rod-shaped
  • Vibrio: Comma-shaped
  • Spirillum: Spiral-shaped
• Bacteria are found almost everywhere and can be:
  • Photosynthetic autotrophs
  • Chemosynthetic autotrophs
  • Heterotrophs

Types of Bacteria

1. Archaebacteria

   • Halophiles: Salt-loving bacteria
   • Thermoacidophiles: Found in hot springs
   • Methanogens: Found in marshes and guts of ruminant animals (produce methane gas).

2. Eubacteria

   • Photosynthetic autotrophs: Example - Cyanobacteria like Anabaena (nitrogen fixation using heterocysts).
   • Chemosynthetic autotrophs: Oxidize inorganic substances (e.g., nitrates, ammonia) for ATP production.
   • Heterotrophic bacteria: Decomposers, curd formation, antibiotic production, nitrogen fixation, or disease-causing (e.g., cholera, typhoid).

3. Mycoplasma

   • Lack a cell wall.
   • Smallest living cells.
   • Survive without oxygen and are pathogenic in plants and animals.

KINGDOM PROTISTA

• Includes all single-celled eukaryotes.
• Protists act as a link between plants, animals, and fungi.

Types of Protista

1. Chrysophytes:

   • Include diatoms and golden algae.
   • Diatoms: Silica cell walls; form diatomaceous earth, used in polishing and filtration.

2. Dinoflagellates:

   • Marine and photosynthetic.
   • Two flagella (one longitudinal and one transverse).

3. Euglenoids:

   • Flexible body with a pellicle.
   • Photosynthetic in sunlight but become heterotrophic in its absence.

4. Slime Moulds:

   • Saprophytic; form a plasmodium on decaying material.
   • Resistant spores survive for years.

5. Protozoans:

   • Amoeboid: Use pseudopodia (e.g., Amoeba).
   • Flagellated: Use flagella; cause diseases like sleeping sickness (e.g., Trypanosoma).
   • Ciliated: Use cilia for movement (e.g., Paramecium).
   • Sporozoans: Infective spore stage (e.g., Plasmodium causes malaria).

KINGDOM FUNGI

• Fungi are non-chlorophyllous organisms with:
  • Hyphae: Network called mycelium.
  • Cell wall: Made of chitin and polysaccharides.
• Found in warm and humid environments.
• Nutrition:
  • Saprophytic (decomposers), parasitic, or symbiotic (e.g., Lichen).

CLASSES OF FUNGI

1. Phycomycetes

   • Grow on decaying material.
   • Asexual spores: Zoospores or aplanospores.
   • Example: Rhizopus, Albugo.

2. Ascomycetes (Sac Fungi)

   • Asexual spores: Conidia (exogenously).
   • Sexual spores: Ascospores (endogenously in ascus).
   • Example: Aspergillus, Neurospora.

3. Basidiomycetes

   • Asexual spores absent; reproduction by vegetative fragmentation.
   • Basidium produces four basidiospores.
   • Example: Agaricus, Ustilago.

4. Deuteromycetes (Fungi Imperfecti)

   • Sexual forms are unknown.
   • Saprophytic or parasitic.
   • Example: Alternaria, Colletotrichum.

VIRUSES, VIROIDS, AND LICHENS

Viruses

• Acellular structures discovered by D.J. Ivanowsky.
• Consist of nucleic acid (DNA/RNA) and protein coat capsid.
• Inert outside host cells but replicate using host machinery.
• Diseases: Mumps, smallpox, AIDS.

Viroids

• Discovered by T.O. Diener.
• Infectious RNA without a protein coat.
• Causes potato spindle tuber disease.

Lichens

• Symbiotic association between:
  • Phycobiont (algal component for food).
  • Mycobiont (fungal component for shelter and nutrients).
• Indicators of pollution as they do not grow in polluted areas.

QUESTIONS

Very Short Answer Questions (1 mark each)

1. Function of heterocysts in Nostoc and Anabaena.
2. Group comprising single-celled eukaryotes.
3. Chief producers in oceans.
4. Fungus causing rust and smut in wheat.
5. Ascomycetes used in biochemical and genetic work.

Short Answer Questions-II (2 marks each)

6. Bacterial classification based on shape.
7. Mode of reproduction in bacteria.
8. Cause and harmful effects of red tides.
9. Structural and disease differences between viruses and viroids.
10. Fungal class with unicellular and multicellular members; define coprophilous fungi.

Short Answer Questions-I (3 marks each)

11. R.H. Whittaker's five-kingdom classification and its criteria.
12. Steps in the sexual cycle of fungi.
13. Describe symbiotic organisms that act as pollution indicators.

Long Answer Questions (5 marks each)

14. Major groups of primitive animal relatives (protozoans).
15. Differentiate fungal classes based on mycelium, spores, and fruiting bodies with examples.

ANSWERS

Very Short Answers

1. Nitrogen fixation.
2. Kingdom Protista.
3. Diatoms.
4. (i) Puccinia (rust), (ii) Ustilago (smut).
5. Neurospora.

Short Answers-II

6. Bacillus, coccus, vibrio, spirillum.
7. Fission; spore formation; DNA transfer (sexual).
8. Red tides by dinoflagellates like Gonyaulax; toxins harm marine life.
9. Refer to "Points to Remember."
10. Ascomycetes; fungi growing on dung are called coprophilous.

Short Answers-I

11. R.H. Whittaker; criteria include cell structure, nutrition, reproduction, and phylogeny.
12. Plasmogamy → Karyogamy → Zygotic meiosis → Dikaryophase (Ascomycetes/Basidiomycetes).
13. Lichens; symbiosis of algae and fungi.

Long Answers

14. Refer to Protozoans classification.
15. Differences between fungal classes (NCERT reference).

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