Biology Essentials - Lecture 5: Essential Characteristics and Conservation

Introduction to Life

• Tree of Life: A representation of the evolutionary relationships among various biological species or entities.
  • Key Groups:
    • ARA (Archaea)
    • UKaria (Eukarya)
    • Bacteria
• Key Insight: Humans are more closely related to ARA than to bacteria.
• Commonality in Life: All life shares certain characteristics, e.g., DNA.

Key Concepts Discussed

1. Genetic Code

• DNA:
  • Universal genetic material.
  • Found in all life forms.
  • Example: Genes from jellyfish causing bacteria to glow.
  • Interchangeability: DNA can be transferred among different organisms.
  • Suggests a common ancestor for all life.

2. Central Dogma

• Overview:
  • DNA → RNA → Proteins → You
  • Process includes DNA replication, transcription, and protein synthesis.
• Francis Crick: Key figure in understanding DNA's function.
• Universality:
  • Applies to all life forms, including bacteria, despite different ribosomes.

3. Metabolic Pathways

• Metabolism:
  • Conversion of energy within organisms.
  • Cellular respiration: Organic material + Oxygen → CO2 + Water.
• Energy Coinage:
  • ATP production through pathways like glycolysis, Krebs cycle, and oxidative phosphorylation.
  • Fundamental pathways are shared across all life.

Eukaryotic Characteristics

• Domains: Bacteria, Archaea, Eukarya.
• Eukaryotic Cells:
  • Have nuclei.
  • Division of labor inside cells.

Ways Eukaryotic Cells Evolved

1. Endomembrane System

• Internal Folding:
  • Increases surface area, enabling complex functions.
  • Includes structures like Golgi apparatus, endoplasmic reticulum.
• Molecular Evidence:
  • Proteins show inverse placement inside and outside of cells.

2. Organelles

• Mitochondria & Chloroplasts:
  • Result from endosymbiosis.
  • Resemble bacteria (own DNA, reproduce by binary fission).
  • Chloroplasts: Important for photosynthesis.

Conclusion

• Evolutionary Solutions:
  • Once a solution is found, it is conserved and passed through the tree of life.
  • The fundamental characteristics decided billions of years ago are still conserved.