Lecture 1

• Eukaryotes


  Cells with linear chromosomal DNA packed into a membrane-enclosed nucleus, also contain membrane enclosed organelles (mitochondria and/or plastids)
• Prokaryotes


  Cells have no nucleus and no membrane-enclosed organelles; DNA contained in a circular chromosome and plasmids
• Euglenozoans, Forams, Diatoms, Ciliates, Red algae, Green algae, Plants, Tubulinids, Fungi, Animals are all part of the Domain Eukarya
• Euryarcheotes, Thaumarchaeotes, Crenarcheotes, Proteobacteria, Chlamydias, Spirochetes, Gram-positive bacteria, Cyanobacteria are all part of the Domain Archaea and Domain Bacteria
• Eukaryotes are nested within Archaea in the tree of life
• How do prokaryotes obtain energy?


  • Autotrophs - generate their own food from inorganic molecules
  • Heterotrophs - consume food produced by other organisms
  • Chemotrophs - energy comes directly from chemical reactions
  • Phototrophs - energy comes from light
• Not all photoautotrophs do oxygenic photosynthesis
• Aerobic vs. Anaerobic metabolism


  Can the organism live in the presence of oxygen or not, respectively
• Binary fission


  After doubling in size, single cell splits into two cells
• DNA in prokaryotes is generally organized into a single circular chromosome plus many smaller circular plasmids
• Archaea


  Generally extremophiles with anaerobic metabolisms, found in harsh anoxic environments, some are chemoautotrophs that thrive around volcanic vents
• Bacteria


  Highly diverse group that contains species that live by virtually every mode of nutrition and metabolism possible, some are parasites and pathogens, many play critical ecological roles as decomposers and symbionts
• Earth lacked life as we know it for the first billion years, until ~3.8 bya there were periods of heavy bombardment, atmosphere was rich in N2, NH4, and CO2 but lacked O2
• First evidence of prokaryotic life in fossil record ~3.5 bya, stromatolites were likely photoautotrophs but without oxygenic photosynthesis
• Cyanobacteria are photoautotrophs that capture light energy through oxygenic photosynthesis, at first O2 oxidized abundant iron in the oceans, then the "Oxygen Revolution" occurred, increasing O2 in the atmosphere and forming ozone layer
• Key Terms


  • Prokaryote
  • Eukaryote
  • Anaerobe / Aerobe
  • (Photo- and Chemo-) Autotroph / Heterotroph
  • Plasmid
  • Binary Fission
  • Stromatolite
  • Plastid