Diversity of Life

From taxonomy to phylogeny

What good is taxonomy?

1. A human endeavor!
2. Organizing all of life
3. Identification of the unknown
4. Common characteristics are shared by related organisms 
5. Clues about ancestry: phylogenetics

The binomial system of nomenclature

1. All species have a 2-part name: Genus species (e.g. Homo sapiens)
2. Each genus belongs to a Family 
3. Every family is part of an Order
4. Orders belong to a Class
5. Each class is part of a Phylum
6. All phyla belong to one of the 3 domains
7. Sometimes we still use kingdoms

Phylogenetics: An evolving taxonomy

1. Five kingdoms or 3 domains?
2. Building a relationship: Shared characteristics
3. Caution: Homology vs. analogy
4. A "family tree" according to ribosomal RNA
5. The diversity of life

The 3 Domains of Life

A. Domain Bacteria

1. Unicellular prokaryotes
   • No nucleus!
   • Cell wall: peptidoglycan
   • Endospores: Bacillus, Clostridium
   • Flagella for motility
2. Three basic shapes
   • Coccus
   • Bacillus
   • Spiral
3. 3 common arrangements
   • Strepto = chains
   • Staphylo = clusters
   • Diplo = pairs
4. Size:
   • E. coli: 1 - 2 um
   • Epulopiscium: 500 um
5. Nutrition & Energy
   1. Most are chemoheterotrophs: organic compounds
   2. Some are photoautotrophs: Light + CO2
   3. A few are chemolithotrophs: Inorganic chemicals
6. Growth
   1. No nucleus means no mitosis!
   2. Most divide by binary fission
   3. Can double in numbers every 15 minutes!
7. The roles of bacteria
   1. Disease-causing bacteria: pathogens
   2. Producers: food and oxygen
   3. Nutrient cycling & decomposition
   4. Biotechnology & Bioremediation
   5. Food production & safety
8. The Diversity of Bacteria
   1. Gram negative bacteria
      • Enterobacteria: E. coli and Salmonella
      • Symbiotic bacteria: Rhizobium
      • Spirochetes: Borrelia
      • Photosynthetic bacteria: Cyanobacteria
   2. Gram positive bacteria
      • Staphylococcus: a common skin inhabitant
      • Streptococcus: "strep throat"
      • Lactobacillus: a "probiotic"
      • Bacillus and Clostridium: endospores make them tough to kill
      • Actinomycetes: fungus-like, common in soil
      • Mycobacteria: TB and leprosy

B. Domain Archaea

1. Unicellular prokaryotes
2. No peptidoglycan in their cell walls
3. Extreme habitats
   • Halophiles: salt-lovers
   • Extreme thermophiles: Pyrococcus loves boiling water
   • Thermoacidophiles: Sulfolobus bathes in hot acidic water
   • Methanogens: anaerobes that make methane

C. Domain Eukarya

1. The protists
   • Algae
   • Protozoa
   • Slime molds
2. Kingdom Fungi
3. Kingdom Plantae
4. Kingdom Animalia

D. The Viruses

1. Size
2. Structure
3. Metabolism
4. Reproduction
5. Notable points
   1. Viruses can cause cancer
   2. Viruses mutate easily
   3. Viruses account for a majority of emerging disease
   4. Viruses can remain dormant in their host
   5. Viruses can infect plants, animals, protists, fungi & bacteria
   6. Viruses do not respond to antibiotics