Biological Classification Lecture Notes

Overview

• Classification: The systematic categorization of organisms into distinct groups.
• Two Kingdom System: Proposed by Linnaeus, classifies organisms into Plantae and Animalia.

Key Concepts

Classification Systems

1. Two Kingdoms:

   • Plantae: Photosynthetic organisms.
   • Animalia: Non-photosynthetic organisms.

2. Five Kingdoms (Proposed by R. Whittaker):

   • Monera: Prokaryotic organisms (bacteria).
   • Protista: Unicellular eukaryotes.
   • Fungi: Multicellular organisms with cell walls made of chitin.
   • Plantae: Multicellular photosynthetic organisms.
   • Animalia: Multicellular heterotrophic organisms.

3. Six Kingdoms:

   • Bacteria: True bacteria.
   • Archaea: Ancient bacteria.
   • Protista: Diverse group including algae and protozoans.
   • Fungi: Organisms that decompose and absorb nutrients.
   • Plantae: Photosynthetic plants.
   • Animalia: Animals, including humans.

Criteria for Classification

• Cell Structure: Prokaryotic vs. Eukaryotic.
• Body Organization: Unicellular vs. Multicellular.
• Mode of Nutrition: Autotrophic vs. Heterotrophic.
• Reproductive Modes: Asexual vs. Sexual reproduction.
• Evolutionary Relationships: Phylogenetic ties among organisms.

Specific Organism Examples

Kingdom Monera

• Types of Bacteria:
  • Coccus (spherical), Bacillus (rod-shaped), Spirillum (spiral).
  • Nutritional Types:
    • Autotrophic: Photosynthetic (cyanobacteria).
    • Heterotrophic: Decomposers, pathogens.

Kingdom Protista

• Types:
  • Protozoa: Unicellular, e.g., amoeba, paramecium.
  • Algae: Photosynthetic, e.g., diatoms, euglenoids.
• Characteristics: Mostly aquatic, various locomotion methods (flagella, cilia).

Kingdom Fungi

• Characteristics:
  • Mostly multicellular, cell walls made of chitin.
  • Nutritional Types: Saprophytic, parasitic, and mutualistic (mycorrhizae with plants).
• Reproduction Modes: Asexual (budding, fragmentation) and sexual reproduction (spores).

Viruses

• Structure: Acellular, consisting of protein coat (capsid) and genetic material (RNA or DNA).
• Classification: Plant viruses, animal viruses, and bacteriophages.
• Characteristics: Obligate parasites; cannot replicate outside a living host.

Important Questions & Concepts

1. What is the role of heterocysts in nitrogen fixation?
   • Specialized cells in cyanobacteria for nitrogen fixation.
2. What are the main characteristics of viruses?
   • They are acellular, require a host for replication, consist of protein and genetic material.
3. What are the uses of diatomaceous earth?
   • Used for filtration and as a polishing agent due to its accumulation over time from diatoms.

Conclusion

• Classification helps understand the relationships and functions of organisms in the ecosystem.
• Advances in classification systems reflect new discoveries in biology and genetics.