Overview
This lecture covers the five-kingdom classification of living organisms, with emphasis on the Monera (bacteria) and Protista kingdoms, their key differences, cell structures, nutrition, examples, and related biological concepts.
Five-Kingdom Classification
- Organisms are classified into Monera, Protista, Fungi, Plantae, and Animalia.
- Key differences include unicellularity vs. multicellularity, prokaryotic vs. eukaryotic cells, presence/absence of cell wall, nuclear membrane, and nutrition types.
Kingdom Monera (Bacteria)
- Includes all prokaryotes, mainly bacteria, which are unicellular organisms.
- Lack double-membrane cell organelles (e.g., nucleus, mitochondria).
- Ribosomes (involved in protein synthesis) are present in both prokaryotes and eukaryotes.
- Genetic material can be DNA or RNA, transferred to offspring via cell division.
- Bacterial cell walls are usually made of peptidoglycan; some exceptions exist (mucopeptide).
- Bacteria are cosmopolitan—found everywhere.
- Types include Eubacteria, Archaebacteria (can survive extreme environments), Cyanobacteria, and Mycoplasma.
- Mycoplasma are the smallest, lack a cell wall, and are called "Joker of the Plant Kingdom."
- Bacteria vary in shape: spiral (spirillum), round (coccus), comma-shaped, etc.
- Some bacteria have flagella (thread-like structure) for movement.
- Bacteria are divided into Gram-positive and Gram-negative based on cell wall structure and staining.
Bacterial Nutrition
- Bacteria may be autotrophic (self-synthesizing food) or heterotrophic (depend on others).
- Autotrophic nutrition includes phototrophic (using light) and chemotrophic (using chemicals like sulfur).
- Cyanobacteria (blue-green algae) carry out photosynthesis using light-absorbing pigment.
- Chemotrophic bacteria (e.g., Thiobacillus) use chemicals like sulfur for nutrition.
Kingdom Protista
- Protists are unicellular eukaryotes with membrane-bound organelles (nucleus, mitochondria, etc.).
- Examples: Amoeba, Plasmodium (malaria parasite), Paramecium.
- Protists can be autotrophic, heterotrophic, or both; some are parasitic (e.g., Plasmodium, Entamoeba).
Key Terms & Definitions
- Prokaryote — organism without a nucleus or double-membrane organelles (e.g., Monera).
- Eukaryote — organism with nucleus and organelles (e.g., Protista).
- Peptidoglycan — substance making up most bacterial cell walls.
- Flagellum — threadlike structure for movement in bacteria.
- Gram Stain — method to classify bacteria based on cell wall.
- Ribosome — cell structure for protein synthesis.
- Autotrophic — organism making its own food.
- Heterotrophic — organism depending on others for food.
- Cyanobacteria — photosynthetic bacteria, also called blue-green algae.
- Mycoplasma — bacteria without cell wall, smallest unicellular organism.
Action Items / Next Steps
- Review notes on fungi and plants for next class.
- Understand key differences between Monera and Protista for potential exam questions.
- Write down the photosynthesis equation as covered.