Lecture Notes on Prokaryotes and Evolution

Key Features of All Organisms

• Common Features:
  • Ribosomes: Present in all organisms including prokaryotes.
  • DNA & RNA: Genetic material for all organisms, supporting the common ancestor theory.
  • Cell Membranes: Essential for defining living things.
• Metabolic Pathways:
  • Cellular Respiration: Uniform process across all organisms.
  • Semi-conservative DNA Replication: Each new DNA molecule retains one original strand.

Prokaryotic Cells

• Characteristics:
  • Unicellular
  • Divide by binary fission
  • Circular DNA, not enclosed in a nucleus
  • No membrane-bound organelles
• Basic Structure:
  • Plasma membrane, potential cell wall or capsule
  • Ribosomes and DNA

Domains of Life

• Three Domains:
  • Archaea
  • Bacteria
  • Eukarya
• Endosymbiosis Theory:
  • Eukaryotes evolved from an archaea that engulfed bacteria (mitochondria, chloroplasts).

Bacteria Characteristics

• Cell Wall and Staining:
  • Peptidoglycan: Differentiates Gram-positive (thick, purple) and Gram-negative (thin, red) bacteria.
• Shapes:
  • Spherical (Cocci)
  • Rod-shaped (Bacilli)
  • Spiral (Spirilla)

Archaea Characteristics

• Unique Features:
  • RNA differences distinguish them from bacteria.
  • Unique cell membrane lipids (ether linkages).

Genetic Transfer in Prokaryotes

• Lateral Gene Transfer:
  • Conjugation: Direct exchange via a pilus.
  • Transformation: Uptake of DNA from the environment.
  • Transduction: Viral-mediated DNA transfer.

Antibiotic Resistance

• Mechanism:
  • Mutation leading to survival and replication of resistant strains.
  • Lateral transfer of resistance genes.

Diversity & Ecology of Prokaryotes

• Extremophiles: Bacteria thriving in extreme conditions (e.g., thermophiles).
• Environmental Role:
  • Vital for ecosystems, nutrient cycling.
  • Most bacteria are beneficial, not harmful.

Examples of Bacteria

• Actinobacteria: Source of antibiotics, can cause tuberculosis.
• Cyanobacteria: Photosynthetic, precursor to plant chloroplasts.
• Proteobacteria: Includes E. coli, related to mitochondrial ancestor.

Methanogens and Environmental Impact

• Methanogens: Archaea producing methane, significant in gut flora.
• Environmental Concerns:
  • Methane as a greenhouse gas.
  • Contribution to climate change by livestock emissions.

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Study Tips

• Focus on understanding the differences in cell structure amongst bacteria, archaea, and eukaryotes.
• Review the processes of lateral gene transfer and their implications for genetic diversity.
• Understand the ecological roles and impacts of prokaryotes in various environments.