Lesson #5 (summarized) - Classification of Eukaryotic vs. Prokaryotic

Linnaeus' Classification System

  • Recognized only two kingdoms: animals and plants.
  • Microscopes led to better understanding of cellular structures.

Classification of Living Things

  • Domains: Eubacteria, Archaea, Eukaryotes
  • Kingdoms: Eubacteria, Archaea, Protista, Fungi, Plantae, Animalia
  • Key differences in cell type, cell structures (e.g., cell walls), number of cells (unicellular vs. multicellular), and mode of nutrition (autotroph vs. heterotroph).

Domains of Life

  • Eubacteria: Kingdom Eubacteria.
  • Archaea: Kingdom Archaea.
  • Eukaryotes: Kingdoms Protist, Animals, Plants & Fungi

Species Concepts

  • Morphological: Focuses on form and structure.
  • Biological: Ability of organisms to breed and produce viable/fertile offspring.
  • Anatomical Evidence: Homologous bone structures indicate shared evolutionary history.
  • Physiological Evidence: Biochemistry of organisms, like protein/enzyme structure (e.g., insulin in guinea pigs).
  • Phylogenetic: Evolutionary relationships among organisms, including DNA sequences.

Prokaryotes (Eubacteria & Archaea)

  • Single-celled, lack membrane-bound organelles and a nucleus.
  • DNA in nucleoid region.
  • Smallest organisms, dominant in every habitat.

Importance of Prokaryotes

  • Some bacteria are pathogens (disease-causing agents).
  • Play roles in ecosystems as decomposers and producers.
  • Recycle nutrients in biogeochemical cycles (nitrogen-fixing bacteria).
  • Photosynthetic bacteria produce atmospheric oxygen.
  • Mutualism: Relationships where both species benefit (e.g., bacteria in human intestines producing vitamins).
  • Produce antibiotics (kill or weaken microorganisms).

Eukaryotes

  • Multicellular with membrane-bound organelles and a nucleus.
  • Internal membranes from folded cell membrane of ancestral prokaryotes increased surface area for material exchange.
  • Mitochondria and chloroplasts originated via endosymbiosis
    • Mitochondria + Aerobic \,prokaryotes \rightarrow Proteobacteria
    • Chloroplast + Photosynthetic \,prokaryotes
  • Endosymbiosis: A single-celled organism lives within another organism's cells.